[BidClub_]
Lex Fridman Podcast · · 222 min

Dave Hone: T-Rex, Dinosaurs, Extinction, Evolution, and Jurassic Park | Lex Fridman Podcast #480

Lex FridmanDave Hone

YouTube ↗
TL;DR

  • T. rex’s durable advantage was an extreme package of scale, force and locomotor efficiency, not cinematic sprinting. At roughly 12 meters long, seven-plus metric tons and perhaps 40 kph only at the upper estimate, it was “an orca on land,” power-walking on spring-efficient feet while a 2.5–3-meter tail muscle drove each stride. Hone said some contemporaneous carnivores were only a little bigger than Velociraptor; Lex compared that ecological gap to lions alongside a weasel, while its likely prey base contained abundant juvenile megaherbivores.

  • The best-supported hunting thesis is lower-risk endurance predation on juveniles, combined with opportunistic scavenging. Modern and fossil evidence suggests carnivores typically take prey around 5–20% of their own mass; young dinosaurs were smaller, poorly armored, inexperienced and pushed into inferior feeding grounds. Healed tyrannosaur bites establish active attacks, while bites laid over weathered bone establish scavenging: “They’re obviously both.”

  • Paleontology’s core model risk is mistaking one preserved event for a species-wide strategy. A Microraptor containing one fish does not establish fish specialization, three parallel tyrannosaur trackways do not establish coordinated hunting, and several bodies in one quarry may have washed together. Hone’s preferred standard is converging, independent evidence—mechanics, isotopes, stomach contents, bite marks, tracks and living-animal analogues—paired with explicit alternative explanations.

  • The commercial fossil market is pricing celebrity and scarcity far more aggressively than scientific utility. Stan sold for $31.8 million, while the less complete Stegosaurus Apex later reached roughly $40 million; yet Sophie, described as by far the most complete known Stegosaurus, sold about a decade earlier for roughly £250,000, or $400,000. Hone’s reaction is essentially art-market logic: “It’s worth what people will pay for it,” with the 100-fold repricing difficult to explain through specimen quality alone.

  • The highest-return research capital may be infrastructure and repeated sampling rather than trophy acquisitions. Given $10 billion, Hone would spend perhaps half a billion on a first-rate museum, fund excavations from a durable endowment, and buy productive quarries so trained workers could send every find directly to public collections. His sharper point is that paleontological data are perishable—“our science is literally disappearing”—while drones, seismic sensing, radioactivity detection and medical scanners have not displaced people walking exposed rock.

  • Jurassic Park demonstrates how scientific authenticity can compound—or erode—an entertainment franchise’s cultural value. The first film broadly captured T. rex’s size and power-walking gait, but the franchise embedded inventions such as motion blindness, giant featherless Velociraptors and assumed pack hunting; later films even regressed from accurate models despite accuracy requiring “no more hassle.” The offsetting legacy is tangible: the Jurassic Foundation has funded dinosaur research and helped young scientists enter the field.

  • Evolution rewards scale and specialization during normal conditions, then reverses those gains under regime change. Bigger animals gain efficiency, dominance and dietary reach, but require more land and food, reproduce slowly and carry less population-level genetic diversity; the asteroid-driven climate shock therefore hit large terrestrial dinosaurs especially hard. Birds—10,500–11,000 living dinosaur species—show that survival came through small-bodied lineages, while T. rex shows why the locally dominant incumbent can still be the most exposed when the environment resets.

Digest · the substance, structured for research

1. T. rex was an orca-sized predator operating on land

  • Hone begins with scale that museum mounts flatten into abstraction: T. rex was roughly 12 meters long, 4.5–5 meters to the head and seven-plus metric tons. His downstairs skull cast is not unusually large, yet he could fit through its mouth; colleague Tom Holtz’s compression is exact: “an orca on land.”

  • That makes a large savanna elephant, at five or six tons, lighter than the biggest T. rex—and the dinosaur was both bipedal and carnivorous. A 200-kilogram lion is not remotely comparable; the operative impression would be “just how absolutely vast they are.”

  • Hone’s zoo analogy explains why public intuition stays weak. Elephant houses, doors, barriers and food are all built to elephant scale, while mounted dinosaurs sit beyond rails and above platforms; only underneath one does the reference point click: “the foot finishes at my knee.”

  • Its recognition is similarly oversized. Alongside lions, elephants, giraffes, tigers, hippos and rhinos, T. rex is among the few animals almost everyone can name, so it “just dominates conversations” for dinosaur and tyrannosaur researchers.

2. The skull was built around crushing force, while the arms were fading away

  • T. rex carried a boxy, heavily reinforced skull with forward-facing, tennis-ball-sized eyes and teeth thick enough to withstand enormous loads. A similarly long Carcharodontosaurus tooth is only about one-third as wide; T. rex combined that thickness with “this uber-powerful bite” capable of driving through bone.

  • The arms tell the opposite story. Their deltopectoral crests were modest, radius and ulna thinner than a human’s, claws less curved than those of many theropods, and ligament pits exceptionally small for a tyrannosaur—all signals that the two functional fingers were “not doing very much at all.”

  • Scale resolves the visual confusion: the arm looks dangerous beside a person, but not on a seven-ton animal whose individual teeth approach finger size. A sometimes-preserved extra metacarpal is not evidence of a working third digit.

3. Locked feet and a massive tail made bipedal gigantism efficient

  • Tyrannosaur metatarsals formed an interlocking arrangement in which the middle bone narrowed and was braced by its neighbors. The same feature evolved independently in ornithomimosaurs and other groups; by preventing the foot from splaying, it redirected each landing into ligaments and cartilage that returned a little energy “every single step.”

  • The real engine sat in the tail. A huge muscle across its first third to half—perhaps 2.5–3 meters long in T. rex—attached to the femur; when it contracted, the planted foot stayed still and the body moved forward. Humans use the butt for comparable work, while dinosaurs used “a giant set of muscles” behind the hips.

  • Detailed speed estimates have moved repeatedly, but Hone cites roughly 25 mph, or 40 kph, as a recent upper bound and expects somewhat less. T. rex probably power-walked rather than entering a gait with both feet airborne, yet a four- or five-meter stride still covered ground rapidly.

  • Lex’s robotics analogy lands because the problem is energy management, not merely top speed. Hone adds that cinema itself began with biomechanics: Eadweard Muybridge’s triggered photographs resolved a bet about whether a galloping horse became fully airborne, then became a moving photographic sequence.

4. A human might survive because T. rex was cautious—or because we were uneconomical prey

  • A T. rex had no learned category for a primate-like animal. Hone notes that animals isolated from humans sometimes approach them without a response; a tyrannosaur might find people unfamiliar, threatening or simply “off-putting,” while basic animal caution could delay an attack.

  • Prey economics offers a second possibility. Hone’s work on Microraptor and modern carnivores places typical prey around 5–20% of predator mass; at the lower end, a human may be beneath the worthwhile range of a seven-ton adult, though a one-ton subadult would present a very different calculation.

  • Motionlessness would not make someone invisible: “It’s nonsense. They can see really well.” If one approached in open ground, Hone’s desperate option would be an accurately thrown rock; in woodland, a person could pivot around a large tree faster until the animal lost interest.

5. Juvenile herbivores offered the best risk-adjusted prey

  • Documentaries favor an adult Triceratops showdown, but a predator injured by meter-long horns, a crushed foot or a body slam may never hunt again. Even killing a five-ton hadrosaur is inefficient because one T. rex cannot consume the carcass before much of it rots.

  • Fossils align with lower-risk targeting: swallowed remains and healed bite wounds from large theropods repeatedly involve young animals. “Juvenile” need not mean hatchling—a one-ton Triceratops could still be rhino-sized—yet it remained smaller and less formidable than the adult.

  • Young animals were vulnerable along several dimensions at once: incomplete horns, frills or armor; limited knowledge of predators; inefficient foraging; and higher food requirements relative to size. Adults could also displace them from the best patches into marginal areas or the forest edge “where the T. rexes hide.”

  • Hone treats this as a broad ecological rule of thumb, not dinosaur exceptionalism. Comparable patterns run from fish, starfish and mantises through crocodiles and large cats: juveniles are “dumb, but they’re inexperienced,” and direct dinosaur evidence fits that expectation.

6. Bite marks only become behavioral evidence after reconstructing what happened to the corpse

  • Hone’s governing warning is that fossils “basically can’t” be taken at face value. Several theropods in one quarry might have lived together, but fish scales, debris and bone orientation may instead show that water transported separate bodies into one channel.

  • A Mongolian hadrosaur provided unusually clean sequencing. Erosion marks lay beneath tyrannosaur bites, meaning the carcass died, washed downstream, weathered on a sandbank for days or perhaps weeks, and was bitten later: “It pretty much can’t have happened any other way” than scavenging.

  • Every bite occurred on the humerus. Deep punctures at the ends indicate the large side teeth removing bone, while close parallel scratches clustered along the muscle-bearing deltopectoral crest match the small, flattened front incisiform teeth pulling tissue away.

  • Hone’s analogy is scraping cream from an Oreo after taking off the top. The large teeth killed and dismembered; the small front teeth selectively fed—a distinction recoverable because the pristine remainder of the skeleton carried no comparable damage.

7. T. rex probably pursued prey over distance and scavenged whenever the opportunity arose

  • The energy-efficient foot and long stride point toward persistence rather than cheetah-like acceleration. Hone pictures something more wolf- or hyena-like: approach a juvenile prey animal, begin the chase with distance already closed, and exploit endurance even if the quarry is initially faster.

  • Open habitats make hiding a four-meter-tall predator difficult. Hone therefore suspects some combination of nocturnal activity, excellent smell and large eyes optimized for low light; darkness would let T. rex “sneak”—with the word heavily qualified—close enough to make pursuit viable.

  • Its hunting success need not have approached 100%. A one-ton Triceratops might escape often, but a tyrannosaur already near top speed after covering the first few hundred meters could keep enough pressure on an inexperienced animal to win sometimes.

  • The hunter-versus-scavenger debate is false: weathered bones bitten after death prove scavenging, while healed bones containing tyrannosaur teeth prove attacks on living prey. Hone still guesses active predation predominated because obligate scavengers require the ultra-efficient, long-range travel seen in soaring vultures and condors.

8. Dinosaur diversity remains radically undersampled

  • Hone places T. rex finds from Alberta down toward New Mexico; some tyrannosaurine teeth farther south may or may not be T. rex. Mongolia instead had Tarbosaurus, its exceptionally close relative; dinosaurs more broadly reached Antarctica even near the extinction boundary.

  • Paleontologists have named roughly 1,500–1,600 valid dinosaur species, acknowledging disputes around individual names. The field has nevertheless added around 40–50 species annually for at least 10–12 years, with “no signs of slowing down.”

  • Large geological inventories remain lightly explored. Hone cites India, newly recognized beds in Ecuador, fossil-rich Argentina and Australia as places where known potential greatly exceeds excavation effort.

  • The true historical species count is much harder. Preservation, rock exposure, species duration and sampling push estimates in opposite directions, leaving a range where a numerical guess might be “very accurate or very far out.”

9. Most fossil discovery still means walking the right rocks and noticing millimeters

  • Exceptional feather-bearing deposits are often commercially quarried lithographic limestones with extremely fine layers. Because a good fossil may occur only after hundreds of tons are split, researchers depend on quarry workers already processing the stone rather than assigning paleontologists to shift it all.

  • Elsewhere, the method is largely unchanged since the 18th century: identify rocks of the right age and depositional type, walk exposed surfaces and look. Surface skeletons rarely endure; wind-blown sand, moisture, freezing and porous bone rapidly reduce them to fragments.

  • Hone’s ideal specimen began as less than a centimeter of claw protruding from a northern Chinese hill. Excavation revealed a more than 90% complete Velociraptor relative, later named Linheraptor: “Every so often behind that is a whole skeleton.”

10. Excavation is an engineering problem governed by rock, access and transport

  • Technique begins with the relative strength of fossil and matrix. Soft Chinese or Mongolian sandstone can sometimes be cleared by hand, while fragile bone in hard rock rules out vibration-heavy equipment and may require slow chipping around every surface.

  • Preparators stabilize porous fossils with Paraloid, a consolidant that penetrates bone but can later be dissolved with acetone. That reversibility lets teams strengthen a specimen in the field without permanently locking future researchers into the treatment.

  • After tracing enough bones to infer the skeleton’s orientation, crews remove overburden and isolate a block. That can mean ten people with pickaxes, a backhoe in the desert or 20–30 feet of hill removed across a large area before the fossil layer is even reached.

  • Burlap, plaster and sometimes wooden beams turn the block into a transportable jacket. Where protected land bans wheeled vehicles, teams must subdivide it or shave away every safe gram to meet helicopter limits; a Stan-sized excavation can span months across three or four years.

11. Documentation converts an impressive skeleton into historical evidence

  • Grids, photographs and now drone photogrammetry preserve each bone’s original position. Long bones aligned with one another suggest current flow; absent small bones imply sorting; one anomalous element may belong to another animal washed into the same deposit.

  • Stan required more than 30,000 hours of cleaning, preservation, restoration and documentation. It is roughly 70% complete by bulk and 63% by bone count, with an exceptionally preserved skull that became a standard reference; discovered in 1987, it remained with the Black Hills Institute until about 2020.

  • Borealopelta, a roughly 112-million-year-old armored herbivore, preserved armor, skin, keratin sheaths and stomach contents despite being deposited miles out in an ancient sea. Preparator Mark Mitchell spent close to two years exposing it; color-pattern evidence tentatively supports a darker back and lighter underside, “give or take some very large uncertainties.”

  • Its adults resemble “nearly armored pine cones,” while juveniles appear much less armored. Hone infers that defense was real but probably not the armor’s original primary driver: if preventing predation alone explained it, the most vulnerable babies should have possessed it too.

12. Trophy-fossil prices have detached from completeness

  • Stan’s $31.8 million auction price shocked a market accustomed to major T. rexes selling for a few million. Lex noted that the result required more than one serious bidder to reach that level; the buyer was later identified as Abu Dhabi’s Department of Culture and Tourism.

  • Hone compares the market with art: beyond small fossils, a dinosaur “is worth what people will pay for it.” Apex, the Stegosaurus that subsequently broke Stan’s record at roughly $40 million, strikes him as large and good but not obviously singular enough to explain the premium.

  • Sophie in London is a young, smaller specimen, but Hone calls it “by far” the most complete Stegosaurus, missing only a limited set of plates and bones. It reportedly sold for around £250,000—perhaps $400,000—about a decade earlier, versus roughly 100 times more for the less complete Apex.

  • Size and public recognition deserve some premium, and T. rex sits above even famous names such as Stegosaurus, Triceratops and Diplodocus. Lex framed Apex as roughly 50% more expensive than Stan, but Apex was not a T. rex, making that comparison even harder for Hone to reconcile with specimen quality.

13. Research capital would compound through museums, land and open access

  • Given $10 billion restricted to dinosaurs, Hone would put perhaps half a billion into “the best museum you’d ever seen.” The purpose would be dual: communicate research publicly and provide stable, suitable storage so fragile fossils remain available for study.

  • A further billion could fund excavations and embedded researchers almost indefinitely if invested and spent through its returns. The remainder could acquire productive land and commercial quarries, including exceptional-preservation sites now controlled by miners or passive private owners.

  • His operating model would train every worker, reward discoveries and transfer specimens directly to museums. Researchers would no longer pay for access, and institutions would not need a new donor whenever an important fossil might otherwise end up in “some Silicon Valley billionaire’s foyer.”

  • The emphasis is not merely possession. Owning the source terrain would align search incentives, public preservation and scientific access—turning extractive sites into a durable sampling network.

14. Fossils are a perishable data stream that remote sensing has not rescued

  • Hone jokingly argues that all science funding should temporarily go to paleontology because black holes or panda genetics can still be studied later, whereas exposed fossils erode away. The serious kernel is stark: “Our science is literally disappearing.”

  • A unique giant could emerge from a hillside, weather for six months and vanish before anyone recognizes it. Researchers would then lose not only a marketable object but a biological observation that may never have been preserved anywhere else.

  • Technology has delivered less than Jurassic Park promised. Seismic “thumpers” do not reveal clean skeletons; drones struggle to match binocular human vision and head movement; unusually radioactive bones are detectable but not reliably discoverable from afar.

  • MRI and related imaging also falter because fossil bone absorbs minerals from its matrix and can approach the surrounding rock’s density. Paleontology lacks the funding to customize every promising technology, so for now “humans are quite incredible” at the essential task of looking.

15. Tyrannosaurs spent 100 million years turning a modest design into T. rex

  • Tyrannosaurs extend from roughly 160–165 million years ago to the extinction around 66.5 million years ago. The earliest known forms were two or three meters long, chest-high, long-armed and superficially similar to other small carnivorous dinosaurs.

  • Important traits arrived early: paired nasal bones fused into a rigid snout, flattened front teeth resisted pulling forces, and feathers are directly preserved. By the Early Cretaceous, Yutyrannus reached roughly six to seven meters and perhaps half a ton to a ton while remaining definitively feathered.

  • Later evolution split into long, narrow-snouted alioramins built for faster, lighter bites and robust tyrannosaurines. The latter line progressively enlarged the head and teeth, reduced tooth count and intensified bone-crushing power through Albertosaurus, Gorgosaurus, Daspletosaurus, Tarbosaurus and Tyrannosaurus.

16. Size created daily advantages and catastrophic tail risk

  • Cope’s Rule captures the broad tendency for lineages to grow. Some of it is diffusion from a small starting point, but larger animals can take more prey, travel more efficiently, win contests and dominate territories or mating opportunities.

  • The same strategy fails under extreme stress. Large animals need more food and land, occur in smaller populations and reproduce slowly; a mouse population breeding every eight weeks offers selection far more genetic variation than elephants breeding perhaps once every five years.

  • Dinosaur ecosystems supported several 10-, 20- or 30-ton herbivore species and terrestrial carnivores above one ton—far beyond modern land systems. T. rex was probably the largest expression, but the normal advantages of gigantism lasted only until the environment crossed a threshold it could not service.

17. T. rex was an arch predator in an ecosystem with almost no carnivore peer

  • Hone resists “apex predator” because ecology often uses it for predators of other predators, such as great white sharks consuming tuna or sea lions. Darren Naish’s alternative, “arch predator,” better describes an enormous top carnivore primarily eating herbivores.

  • Hone’s point was that T. rex’s niche was exceptionally lopsided even among giant tyrannosaurs: some contemporaneous carnivores were only a little bigger than the Velociraptor skull. Lex’s analogy was Africa containing lions, then “a weasel about this big,” with nothing substantial between them.

  • That gap does not mean T. rex routinely ate smaller carnivores. An adult Velociraptor-sized animal would be mouse-scale prey to it and probably not worth pursuing, while juvenile Triceratops, Edmontosaurus, Parasaurolophus and even sauropods offered far more return.

  • Against comparable land predators, Hone favors the heavier animal with the stronger bite: T. rex. Carcharodontosaurs likely grappled and slashed prey until it weakened; aggression might upset predictions—“the size of the fight in the dog”—but Velociraptors attacking T. rex would resemble “meerkats killing a lion.”

18. Jurassic Park’s inventions became public default settings

  • The motion-blind T. rex appears to be Michael Crichton’s fiction; Hone searched for the research hinted at in The Lost World and found none. The franchise similarly turned Velociraptor into a tall, cheetah-fast, highly intelligent, featherless pack hunter despite the real animal standing roughly thigh-high.

  • Some fundamentals were strong. The first film made T. rex approximately the right size and shape, and its Jeep pursuit shows a power-walking gait with one foot grounded; Jurassic Park III’s Pteranodons and its reconstruction of Spinosaurus also impress Hone.

  • Later entries regressed. Jurassic World’s Pteranodons could not grasp and fly away with people using their real feet, while its Gallimimus model was actively given teeth despite the animal having a beak—an edit barely visible during its brief appearance.

  • A Hollywood creature designer told Hone accurate revisions require about the same work as inaccurate ones: “It’s no harder to make it accurate.” The first film’s Jurassic Foundation partly repaid paleontology through research grants, but audiences should still treat the franchise like James Bond, not a documentary.

19. Group fossils do not establish coordinated pack hunting

  • The famous Deinonychus–Tenontosaurus association was interpreted as hunters beside their kill, but Hone asks the load-bearing question: “Well, why did they all die there?” Lions do not routinely die beside wildebeest; alternatives include transport, a predator trap or toxins accumulating carnivore bodies around prey.

  • A reported tyrannosaur “group trackway” amounts to roughly four or five prints from three similarly sized animals moving in similar directions. Game trails or males following a female hours apart can create that pattern without social contact, much less cooperative hunting.

  • Even true sociality does not answer the hunting question. Spotted hyenas live in complex clans and appear in dramatic group hunts, yet the scientific literature says they mostly hunt alone; fossil co-occurrence could show shared living without shared pursuit.

20. The gold standard for pack hunting would preserve interaction through time

  • Hone’s hypothetical decisive trackway would contain overlapping sequences: early prints from animal A lie over B, then later B lies over A. That reversal requires contemporaneous movement rather than animals passing minutes or hours apart.

  • If seven or eight such trackways converged on one herbivore and the surface then became chaotic, coordinated hunting would become highly persuasive. Repeated bite marks from differently sized attackers on disproportionately large prey could provide another supporting line, though tooth similarity complicates identification.

  • Deinonychus isotope and feeding studies may eventually strengthen its case; Hone is “not anti the idea.” His objection is transferring even credible behavior between relatives: lions hunt socially while leopards and tigers do not, and spotted hyenas differ sharply from other hyena species.

  • Crocodilians, iguanas and ground hornbills demonstrate that reptile- or bird-like brains do not preclude cooperation. Hone expects some dinosaurs were social and some pack-hunted; his honest conclusion about which ones is: “No idea.”

21. Sexing dinosaurs exposes how little a skeleton can certify

  • Eggs inside a body identify a female immediately, but only a few such specimens exist. Medullary bone offers a broader signal: egg-laying females temporarily grow highly vascular tissue in large bones so calcium can be mobilized rapidly into shells.

  • Its absence proves little. Males, juveniles, females outside breeding season, sick females and those that already laid eggs all lack it; the method identifies “laying female from everything else,” not female versus male.

  • Human pelvic sex differences are poor dinosaur analogues because they reflect childbirth through an unusually demanding birth canal. Horns, crests and body size can also mislead: maned female lions, maneless males and winter-antlered female reindeer show how variable living species remain.

  • Tyrannosaurs nevertheless carried nasal ornament and small horns without obvious mechanical roles. Hone groups likely mating, rivalry and communication functions under “socio-sexual selection,” because signals that attract mates may simultaneously intimidate competitors.

22. Honest signals convert biological cost into credible information

  • Dark-maned lions illustrate the trade: females prefer darker males and rivals find them intimidating, but black hair increases overheating risk near the equator. The signal remains honest because carrying the cost while surviving demonstrates condition.

  • Black swans provide a mutual version. Both sexes prefer curlier wing feathers, and females with curlier feathers tend to win nesting disputes; because the modified flight feathers make flying harder, they effectively announce, “Look how tough I am.”

  • Theropod crests may have worked similarly. Bright, oversized ornaments reveal a predator to prey, but an animal that still hunts successfully despite conspicuous red-and-yellow structures displays its quality; giant herd-forming herbivores face less need to hide and can push the same logic into enormous horns and frills.

23. Beauty can run away once preference and inheritance reinforce each other

  • The “sexy sons” mechanism does not require an initial survival benefit. If females arbitrarily prefer a novel color, daughters can inherit the preference while sons inherit the color, creating a feedback loop in which each generation becomes both redder and more attracted to red.

  • Wild female mollies preferentially choose male swordtails, which look familiar enough to register as mates but different enough to be exciting. Hone’s interpretation is that variation itself may be attractive because it carries genetic diversity useful against environmental change, parasites and disease.

  • Peacock tails probably mix both mechanisms. Their pigment, size and effect on flight impose a handicap, but extreme form and eye spots likely include arbitrary preference; “pure beauty” is therefore not fully separated from condition, inheritance and historical accident.

  • Sexual reproduction scales this option value across organisms producing dozens, hundreds or thousands of offspring. Humans naturally reason from few children, while many animals can afford vastly more variation and failed experiments.

24. Population samples matter more than isolated spectacular fossils

  • Signals in both sexes may hint at mutual sexual selection and cooperation in reproduction. Puffins, penguins, starlings and parrots need substantial contributions from both parents, so males as well as females benefit from choosing the strongest available partner.

  • Yet more than 90% of dinosaur species are known from one specimen, sometimes only a few bones or a tooth. Hone estimates fewer than ten species—perhaps five or six—have enough good skeletons for serious within-species comparison.

  • Protoceratops is the exceptional dataset: more than 100 good skeletons, perhaps 70–80 in accessible museums, spanning embryos and hatchlings through adults, mostly from one Mongolian locality and a window of roughly 100,000 years. That permits population-level questions about growth, ornament and dimorphism.

  • Hone’s 110-specimen gharial study showed why even that may fail: large females overlap small and medium males, leaving only the biggest males obvious. Drilling a Protoceratops mass-death assemblage for medullary bone might finally separate breeding females; scientifically, “another hundred Protoceratops” could beat 50 novel species.

25. Independent evidence is the antidote to seductive one-off stories

  • Microraptor specimens preserve a mammal, bird, lizard and fish in different stomachs. Each isolated paper could announce a specialist, but together they more plausibly describe generalists—while still leaving open that individuals learned different diets or scavenged unusual meals.

  • The strongest reconstructions ask whether mechanically and historically independent signals converge. One striking fossil is not a “silver bullet”; bone mechanics, habitat, isotopes, gut contents, bite marks and living analogues become powerful when they reach the same answer without depending on one another.

  • Lex’s vanished-human thought experiment clarifies the method. A healed compound fracture would imply months of care and therefore society; widespread treatment of major trauma and bone cancer would imply technology. As Hone puts it, dozens of ordinary skeletons may say little, while “the right one” reorganizes the inference.

26. Spinosaurus was probably a giant wader, not an underwater pursuit predator

  • Spinosaurs combine independent aquatic signals: crocodile-like skull mechanics, near-circular conical teeth suited to gripping wriggling prey, repeated association with watery settings, isotope signatures resembling fish and crocodiles, and fish scales inside the British Baryonyx. Hone cautions that water association is common in the fossil record because burial often occurs in aquatic settings, but argues the spinosaur pattern is stronger than that background effect.

  • Hone does not infer an exclusive fish diet—terrestrial dinosaurs and pterosaurs also carry relevant feeding evidence—but concludes the group lived differently from ordinary theropods. His shorthand for Spinosaurus is “a very weird, giant stork” or heron: water-associated and wading, but “not very” aquatic.

  • Spinosaurus may have reached 15 meters linearly while remaining lighter than T. rex, with a narrow body, elongated rosette-tipped jaws, recessed nostrils, sail, large arms, short legs and a thin paddle-like tail. Related Baryonyx and Suchomimus retained the head and arms without the full exaggerated package.

  • Hone and Tom Holtz “savaged” the strong-swimmer interpretation, and some original proponents later moved toward a non-swimming position. Against T. rex, Spinosaurus’s long weak jaw and neck poorly suited to rotation meet the tyrannosaur’s exceptionally strong neck and crushing bite: “No, I don’t buy it.”

27. Brains, cannibalism and extinction all reward conservative inference

  • Endocasts reveal relative olfactory and optic regions, while CT scans of the bony inner ear can estimate favored sound frequencies. Intelligence is harder: both brain volume and dinosaur body mass may be wrong by 20–30%, letting assumptions manufacture either a genius or a dullard.

  • A controversial estimate placed T. rex near three billion neurons; a rebuttal produced roughly 250 million–1.7 billion, closer to crocodilian expectations. Hone’s scaling check is blunt: most of the T. rex brain cast is smaller than a chimp’s, while the animal weighed seven tons—crocs are capable, “but they’re sure as hell not monkeys.”

  • Cannibalism rests on firmer evidence. Tyrannosaur bones carry tyrannosaur teeth or repeated feeding scrapes without healing; in a T. rex ecosystem, no other carnivore was large enough to make those marks. It was probably occasional because eating one’s own parasite-loaded species is riskier than ordinary prey.

  • The asteroid around 66 million years ago supplied the ultimate reminder. A roughly Everest-sized object traveling about ten times the speed of sound triggered rapid climate and ecosystem collapse; large terrestrial dinosaurs had maximum exposure, while some isolated populations may have persisted briefly—Hone says he would be amazed if none did—but were extraordinarily unlikely to rebuild global dominance.

28. Birds survived because dinosaur evolution had already diversified beyond giants

  • Birds are not merely descended from dinosaurs in a loose sense: “They literally are” dinosaurs, just as humans are apes and mammals. Roughly 10,500–11,000 living species remain, and their lineage coexisted with non-avian dinosaurs for perhaps 100 million years before the impact.

  • Feathers predated birds and occur in tyrannosaurs, dromaeosaurs, troodontids, ornithomimosaurs and other groups. Their likely early functions were dual: insulating warm-bodied animals and enabling communication through colors, erection, seasonal replacement and age-specific plumage.

  • Evolution’s scale is the mechanism. A female ocean sunfish may release up to 300 million eggs; across huge populations and millions of years, rare variations become inevitable. Evolution is not merely rolling dice—it “gets to keep the sixes.”

  • Yet the result is modification, compromise and repurposing rather than perfection. Swim bladders precede lungs, display tusks become digging tools, and one structure can fight rivals, deter predators and acquire food; organisms are “bodge jobs,” while selection keeps editing an inherited plan.

Dave Hone

T. rex is definitely weird, even compared to all the other giant tyrannosaurs that are very closely related to it, because it is by far—ludicrously by far—the largest carnivore in its ecosystem.

Lex Fridman

So it doesn't really have competition, actually.

Dave Hone

I mean, this is a Velociraptor skull. There are some carnivores that are a bit bigger than this, but not enormously so, which were knocking around with T. rex. The skull's the same type of toothed crap.

Lex Fridman

But think about that. That's like going to Africa and going, “Okay, there are lions. What's the next biggest predator?” And it's like, well, there's a weasel about this big. It's that kind of size difference, and you don't get that normally in ecosystems.

It would eat those—the juveniles of the herbivores—but not—

Dave Hone

Oh, yeah, it's going to be eating Triceratops and Edmontosaurus and Parasaurolophus. There's even a couple of giant sauropods knocking around.

Lex Fridman

Got it.

Dave Hone

In some places, it's going to be hoovering them up, but how often is it going to eat something the size of an adult Velociraptor? I mean, they're a fraction of our size, and we're probably too small. This is like lions hunting mice. You're just not going to bother. Unless one virtually runs into your mouth, you're not going to try and eat it.

The following is a conversation with Dave Hone, a paleontologist, expert on dinosaurs, co-host of the Terrible Lizards podcast, and author of many scientific papers and books on the behavior and ecology of dinosaurs. This was truly a fun and fascinating conversation. This is the Lex Fridman Podcast. To support it, please check out our sponsors in the description and consider subscribing to this channel. And now, dear friends, here's Dave Hone.

Lex Fridman

Let's start with the T. rex dinosaur, possibly the most iconic predator in the history of Earth. You have deeply studied and written about their evolution, biology, ecology, and behavior, so let's first put ourselves in the time of the dinosaurs and imagine we're standing in front of a T. rex. What does it look like? What are the key features of the dinosaur in front of us?

Dave Hone

It's gigantic. It's almost trite now because everyone knows T. rex is massive. But yes, if you actually stand in front of one, you would be seriously impressed by just how absolutely vast they are.

I've got a copy of a T. rex skull downstairs from my office, and I could fit comfortably through its mouth. So it would be just about capable of swallowing me whole, and I'm a pretty big guy.

Lex Fridman

Your body—you could fit it in its mouth?

Dave Hone

I can fit through it. I can fit through it.

Lex Fridman

Wow.

Dave Hone

Yeah. And it's not even a particularly big one. It's a copy of the one that's in the Smithsonian, and they get bigger than that.

Lex Fridman

You have a to-scale copy.

Dave Hone

Yeah, it's a cast, so it's just a giant mold made and then pulled out like the dentist does your teeth, but very, very big.

So, yeah, they are 12-ish meters long. What's that? 14 yards. Four and a half, maybe 5 meters to the top of the head, standing up. So another 6 yards high. And then 7-ish metric tons. What's that? About 8.5 short tons.

A colleague of mine, Tom Holtz, described them as an orca on land. That's it: a killer-whale-sized animal, but on legs, on land. And those are massive predators.

So you're looking at something absolutely colossal, and I think that is what will stun you. I think people don't realize how big a lot of animals are, which sounds weird, but I used to work in a few zoos. Something I think you notice is that when you go and see things like elephants or giraffes or rhinos, everything's built to the scale of the animal. The elephant house is huge. The doors are huge. The bars are huge. The food is huge.

And so you don't see them in the context of something that you have a good frame of reference for. I learned this when I was at London Zoo and was going into the basement of the old elephant and rhino pavilion. A rhino stuck its head out from a gap in the wall, and the head was twice the size I thought it was once you stood next to it.

And the same with an elephant. I once stood next to an elephant closer than you are to me now, and you go, “Oh, they are so much bigger than I thought.”

And I think it's similar in museums. Even when you get up relatively close to a T. rex skeleton, there's a bit of space between you and it, and then some bars. And then it's usually raised up a little bit on a mount to hold the platform. Then you stand back from that, and you don't actually get to stand under them. When you do that, you realize that the foot finishes at my knee.

Lex Fridman

So is a T. rex bigger than an elephant? Would that be fair to say?

Dave Hone

Yeah. A very large African savanna elephant is 5 to 6 tons, and we're looking at 7-plus. And a biped and a carnivore. So, yeah, a big lion—a big lion is 200 kilograms, so 430 pounds.

Lex Fridman

Well, that's why they consider it to be probably the most epic predator in the history of Earth.

Dave Hone

Yeah, and I think more than that, I think it's one of the most iconic animals, period. If you're listing things that the average person has heard of—lion, elephant, giraffe, tiger, hippo, rhino—there are a few more, but T. rex is coming somewhere up in that list. That's how prominent it is as an animal.

So, yeah, it's almost inescapable as a paleontologist, and then doubly so for me, who works on dinosaurs, and doubly so again because I do work on tyrannosaurs. But, yeah, it just dominates conversations.

Lex Fridman

Well, some of the other features, maybe we can go through.

Dave Hone

Yeah, sure.

Lex Fridman

So, big skull, big head, small hands.

Dave Hone

Massive head. Very boxy. It's very robust. Big, forward-facing eyes. Massive eyes—tennis-ball-sized eyes. These things had amazing eyesight. Giant teeth. There's a cast of a—

Lex Fridman

What?

Dave Hone

Tyrannosaurus rex tooth.

Lex Fridman

What? How—

Dave Hone

I know. So—

It looks a bit bigger than it is. This is all root; this would be stuck in the jaw. This would be supporting it.

Lex Fridman

Right. But that tip part is—the tooth?

Dave Hone

But that—the tip, as you call it. And, yeah, that would comfortably go through pretty much any part.

Lex Fridman

Wow.

Dave Hone

And then you realize just how thick it is. So this is a cast of a thing called Carcharodontosaurus from Africa. You get it down in Niger and a few other places like that. They're very, very big—not as big as T. rex, but not a million miles away.

If you look at the teeth in profile, they're a surprisingly similar shape and not far off in size as well. Then you look at them that way on, and you realize it's a third of the width. So this isn't just massive; it's thick. And, of course, being thick, it makes it strong.

With that giant head, with all that extra bone and then all the extra musculature attached to that giant head, they've got this uber-powerful bite and the ability to just chomp through basically anything they want to. So, yeah, they are truly unusual in that regard. Even compared to a lot of the other very big tyrannosaurs, they're often a step above in their proportions.

Lex Fridman

So, incredible crushing power in the jaw?

Dave Hone

Yeah. And then, as you say, this really short, bull neck, because you've got this massive weight of this head up front that you need to hold up and not tip forwards. Really quite a massive body.

Again, there are 2 or 3 other big carnivorous dinosaurs which people argue, “Oh, maybe they're a little bigger than T. rex, maybe they're a little smaller,” but it's always in terms of length, which is one way of looking at things. Pythons are very long, but they're nothing like as massive as a lion or a tiger. Same thing. T. rex is massive. It is built.

So, really big, barrel-shaped chest, making the body very, very big as well. And so that's why there are things like Giganotosaurus and Mapusaurus from South America. Maybe they get a bit longer, another meter or so in length. But in mass, we're talking about maybe only two-thirds, three-quarters. So T. rex is just massively bigger than basically any other big carnivore we know of.

And then, yeah, little arms, as you say. This is not great, but it's a cast of a T. rex arm. It's not the biggest animal. They do get a bit bigger than this. But as I love showing, it's not a million miles off the size of my own. And I could do with a diet, but I don't weigh 7 tons. So, yeah, it really is pretty small.

Lex Fridman

2 claws, 2 fingers.

Dave Hone

Yeah, 2 fingers. You will see sometimes that they say there's a 3rd. This is a slight misnomer. You do see this extra little bone here? This doesn't turn up in all of them, and it's an extra hand bone. So it's these—the metacarpals. But it's not supporting an extra digit.

Lex Fridman

So, mostly functionality-wise, it wasn't very functional.

Dave Hone

They're not doing very much at all. This is what's called the deltopectoral crest. It's really important for big arm movements because it's deltoids and pectorals. The radius and ulna are really quite thin, thinner than ours. The fingers are pretty stocky. The claws look big and curved, and they are, but other tyrannosaurs, and indeed other carnivores generally, have much more curved claws.

And then they have these little things—where can I see it? There, you can see there's a little mark. That's a ligamentous pit.

What you can imagine is, if you're trying to hold onto something and something's wriggling, you want grip. And there's a risk that you'll just dislocate your fingers. So we have ligaments that hold bone to bone.

If you just put it flat to flat, there's only so much surface area you can attach. Whereas if you turn that into a little hemispherical dip, you get a lot more surface area for your ligament, if that makes sense.

Lex Fridman

Yeah.

Dave Hone

So if you have a really big ligamentous pit, it means there's a really big ligament, which means your fingers are really strong and they're really resistant to being wiggled around and pulled, as if you've grabbed something that doesn't want you to kill it.

Well, T. rex has probably the smallest ligamentous pits of any tyrannosaur. So that kind of suggests it's not doing very much. And again, when you look at the claws, proportionally, they're not that big and they're not that curved. So even though it looks like quite a wicked thing to us, remember, put this on a 7-ton animal whose individual teeth are the size of entire fingers. Suddenly that arm doesn't look like it's doing very much.

Lex Fridman

What about the feet?

Steve Brusatte

So massive. Again, not surprisingly, you're supporting a colossal amount of weight. But they have this beautiful adaptation in the foot. The equivalent bones in the foot, the metatarsals, for us make up the flat of the feet. But these animals walk like birds. They have 3 toes on the ground, and then the metatarsals stick nearly vertically. That overall extends the length of the leg, so you can walk a little bit faster. You get a slightly bigger stride length.

Don't worry, I've got the right bone here.

Lex Fridman

Nice.

Steve Brusatte

But they also have this really neat adaptation in the middle bone. You can see it on this one quite well. This is actually not a tyrannosaur; this is an ornithomimosaur, one of the really ostrich-like ones, Gallimimus from the first Jurassic Park. It has the same thing.

You can see the normal bones would be really quite long and square and then flat at the top. Instead, this thing shrinks in the middle and turns into a flattened diamond shape. What that means is the bones on either side lock it. In fact, at the top end, it tends to wiggle a bit. It goes left and then right. Of course, what that really does is help these things lock together.

This is an adaptation to lock the foot and make it stable, and we see it in a whole bunch of things that evolved independently. Early tyrannosaurs don't have this. Early ornithomimosaurs don't have this. The oviraptorosaurs—the early ones don't have this, and the later ones acquire it, as do a couple of other groups as well. It's about making the foot stable.

What that really does is make the foot energy-efficient. You can imagine, as an animal, we have some cartilage and ligaments and tendons joining all the bones together and holding joints stable. When you push down, that's going to compress them to a little degree, and when you lift that weight off, they're actually going to spring back. You're going to get a tiny little energy return.

It's the idea of those air soles they put in all the trainers and stuff in the ’90s. It's that same principle. You'll get a little bit of energy return, but of course, with a big force, particularly for a big, heavy animal, it's going to take the path of least resistance. If your bones are all loose in the foot, what they're going to do is tend to splay out, and you're actually going to lose that energy. But if you lock the feet together, the bones can't move, and instead, that's going to further compress those soft-tissue bits and give you a bit more spring.

Lex Fridman

And this is all about the mobility, about the dynamics of the movement.

Steve Brusatte

It makes you more efficient. It means you're putting less energy in to walk, because you're just getting a little bit of spring out of every single step.

Lex Fridman

I should say that I deeply admire people like Russ Tedrake, the Boston Dynamics teams, and the Tesla Optimus robot teams that look at bipedal and quadruped robot movement. They try to make human-like movement—basically, efficient movement. And so the question here is, how the hell is a T. rex of its size, being bipedal, able to move as a predator? It's a weird body shape, is it not?

Steve Brusatte

The big head makes it look more odd, but you look at dinosaurs as a whole, and over a third, probably 40 or 45%, are in the group called theropods, which were all bipeds. T. rex, Allosaurus, Velociraptor, Spinosaurus, and many others that people may have heard of—they're all bipeds built in this way.

There's a whole bunch of ancestral groups that were doing something very similar, including various crocodiles or relatives of crocodiles, and then the birds are bipeds. Birds are actually doing it in a much weirder way than theropods are. Theropods are basically a lizard on its back legs. I'm oversimplifying a lot. I can hear paleontologists screaming, as I've just said, “It's a lizard standing up.” It's not a lizard standing up, but they're doing a lot of the same stuff in the same way.

Functionally, it's really about where you put muscles, because what you really want to do to walk forwards is pull the leg back so that you're pushing the body off. The way they do that is with the musculature on the tail. We don't have a tail, and indeed, even mammals that do have one, like elephants and lions, have a piddly little thing. There's not a lot of muscle there.

But if you look at a lizard, particularly if you look at something like a crocodile, you see this massive block of muscle sitting on the first third to half of the tail. That's what dinosaurs are doing. It's the same thing as lizards and crocs. They have this giant set of muscles on the first half of the tail that's anchoring on the femur—the thigh bone—on the back of that. Muscles contract. That's the one thing they do.

But now you've got a giant muscle. In T. rex, this muscle is like 2.5 or 3 meters long. It's going to be this wide in the middle. So when that contracts, the leg goes back, the foot's stationary on the ground, and the animal goes forwards.

Lex Fridman

So the tail is—

Steve Brusatte

Integral to movement.

Lex Fridman

So it's a huge part of the biomechanics of the movement.

Steve Brusatte

Yeah, we do it with the butt. We're weird in how we organize our muscles. But this is generally probably a better way of doing it, because you can get a really long muscle. And of course, the longer the muscle, the more contraction you can have.

The hyper-version of this is kangaroos. Kangaroos supposedly get more efficient the faster they move. They get so much energy return that when they're moving faster, they get more compression from the landing, meaning they get more spring.

Lex Fridman

So we should be imagining this gigantic, thick tail, big body—

Steve Brusatte

Oh, yeah.

Lex Fridman

Big head.

Steve Brusatte

Yep.

Lex Fridman

And bipedal. How fast does it move?

Steve Brusatte

So this is one of those things that's gone backwards and forwards and backwards and forwards. There was a paper arguing that we'd probably been overestimating various speeds, primarily based on footprints. There have been I don't know how many papers trying to calculate T. rex speed.

The most recent one that was pretty detailed, I think, had it clocked at 25 miles an hour, so 40 kph was the very upper end of the estimate. So probably a bit less than that.

Lex Fridman

Well, that means it can move.

Steve Brusatte

Yeah, so that's the thing. Big things move quick. I've seen rhinos and hippos going at full tilt, and they're a lot quicker than you'd think. At least part of it is simply stride length. When your legs are 3-ish meters long, it's hard not to cover a lot of ground with a single step.

And yeah, big theropods—T. rex—is going to be a power walker. It's not going to run in the conventional biomechanical sense, where both feet are off the ground at once.

Lex Fridman

So it's not running. It's power walking.

Steve Brusatte

Yeah. But when you've got a 4- or 5-meter-long stride, it doesn't really matter whether you're airborne or not.

Lex Fridman

Power walking, so you're never—when you're running, there are moments in time when both feet are off the ground, and you're saying that likely here, one foot is always on the ground.

Steve Brusatte

Yeah, it pretty much has to be for loading.

Lex Fridman

Just because of the mass of the thing? Okay. All right.

Dave Hone

You know, that's the origin of cinema?

Lex Fridman

What's that?

Dave Hone

It's where—this is Eadweard Muybridge. So the origin of cinema was a bet as to whether or not, while running, a horse had all 4 feet off the ground. No one really knew this for sure.

A guy called Eadweard Muybridge—he was British, but he was living in the States—was a keen photographer. He basically did what people have seen the Wachowskis do for The Matrix. He set up a whole row of cameras and a whole bunch of triggers and had a horse run through them, so they took loads of photos. Lo and behold, in one of them, the feet were off the ground. The guy won his bet.

But he also realized that we already had things like zoopraxiscopes—you know, the little thing you spin with a slit? So you see the—

Steve Brusatte

Right.

Lex Fridman

So he did that with horses. And now you have a moving photograph. That's pretty much the origin of cinema: a bet about biomechanics.

Yeah, it's always a good question and a bet, and there you go. You're off to the races. All right, so we're standing in front of this thing.

Steve Brusatte

Yes.

Lex Fridman

How screwed are you and I? We're back in the time of the dinosaurs. What's the probability of our survival?

Steve Brusatte

There are 2 big things to weigh up, which are going to be interesting. Would they even consider us a potential meal? Because we know that animals have never encountered things before. Animals have to learn stuff. And so animals that have never encountered things before often don't have a response because they don't know what their response should be.

Lex Fridman

We should say that during that time, there was nothing that looked like primates.

Steve Brusatte

No. Absolutely nothing.

Lex Fridman

So we would look very weird, right?

Steve Brusatte

We would look weird, yeah. There are lots of really cool records, particularly down in Indonesia and places, where you've got these insane volcanic spires, and they lead to these tiny little valleys. People go in there, and they say, “Yeah, the animals walk up to us.” They've never seen a human. They don't know what it is.

So it might look at us. Animals are fundamentally cautious. It doesn't know if we're a threat. Maybe it might just find us weird or, in some way, shape, or form, off-putting, and so we may not even be considered on the menu.

The other thing is that we might be too small. My suspicion is that we’re not. Carnivores typically take stuff that is much, much smaller than them, despite basically every dinosaur documentary and movie ever showing T. rex hunting an adult Triceratops, which is about the same size as it. Every documentary has to have lions taking down a wildebeest or even a buffalo. These are weird and rare outcomes; they don’t usually happen.

The vast majority of active predation is on stuff much, much, much smaller than you. I totted some of this up for a paper I did on Microraptor, this really small gliding dinosaur from China, where we actually have a bunch of specimens with various stomach contents in them. We were coming up with numbers of about 5% to 20% of the mass being typical for the prey versus the predator.

That’s actually very similar to what we see with modern carnivores, and it’s not far off what we’ve seen even with things like tyrannosaurs, where you occasionally find consumed bones from prey. So, if we put the lower end of that at 5% of the mass of a T. rex, we might actually be okay. If it doesn’t consider us worth the hassle, then assuming you’re encountering a big adult and not a half-size one that maybe only weighs a ton, we might be all right.

Lex Fridman

What would be the survival strategy? There’s something that you criticized as not being true—I guess in Jurassic Park—not moving.

David Hone

Yeah, it’s nonsense. They can see really well. Like I said, T. rex has giant eyeballs. People don’t realize that because, like whales and elephants, they look small compared to the size of the animal. What’s really important for vision is absolute size, not proportional size.

Absolutely, their eyes are gigantic. A guy called Kent Stevens did a paper, and he’s got a really nice graphic of it. If you just put “Stevens T. rex” in there, it’s the one with the googly eyes. There we go. That’s a baseball- or tennis-ball-sized eyeball. When you think about the incredible visual acuity of something like an eagle, which has eyes not much bigger than ours, think about what that’s going to do.

We absolutely know—there have been loads of studies on this in mammals and birds and other things as well—that eyeball size correlates with visual acuity. That can fold in 2 different ways. It can be general sharpness: How well can you see a long way away? For eagles and vultures, that’s really important. Or it can be good vision in low light.

Lex Fridman

And I now discover that there’s a Nature Was Metal subreddit—

David Hone

On Reddit, yeah, for—

Lex Fridman

—which is looking at—

David Hone

—gnarly, gnarly paleo things. Yeah, I come across it occasionally.

Lex Fridman

For dinosaurs, let’s see what the top post of all time is.

David Hone

Oh, that’s a glyptodontid.

Lex Fridman

An Argentinian farmer recently found a 20,000-year-old fossilized glyptodont.

David Hone

These are giant armadillo-like animals with club tails.

Lex Fridman

Interesting. Wow.

David Hone

Oh, that’s Black Beauty, and that’s at the Royal Tyrrell Museum. So, with giant eyeballs, they can either see very well and see a very long way in daylight, or they can see very well at night. My suspicion is that it’s the latter. I think they’re probably primarily nocturnal when they get that size.

Lex Fridman

Well, not moving might be a good strategy because it’s cautious; it doesn’t understand what these primates are.

David Hone

Yeah, but I think if it starts coming toward you, if you’re truly in the open, then you’re in real trouble, and I’m not sure what you do. The one advantage humans have over almost anything else on Earth—there are a handful of exceptions—is range. I can pick up a rock and hurl it with reasonable accuracy.

Most things can’t do that, and animals probably don’t like being hit in the face or hit in the eyes with a rock at a range because, again, they’re not going to know how it happened or how to respond to it. All they know is that they’re taking damage, and that’s bad. That might genuinely be enough to do it.

I wouldn’t want to try, but again, if I was dumped on a plain or a prairie with nothing else but a T. rex that was interested in me, it’s worth a shot. If you’re in the forest, I would try to get behind a tree. They’re quite good at turning. There have been a couple of nice papers looking at the mechanics of the foot and the ankle and how quickly they could pivot.

But we’re much better because we’re just so much smaller. It would be very Looney Tunes, but I think you could go round and round a big tree—yeah, but much faster than it could. It’s going to get bored or lose interest sooner or later.

Lex Fridman

So let’s zoom out. What did it eat?

David Hone

You could go for the classic joke of “whatever it wanted,” but the reality is that, with the relatively big herbivores that were around at the time, it was probably largely leaving them alone. Again, just consider the classic dynamics of predators, even so-called superpredators like Tyrannosaurus. They’re still real animals. If you get injured and you can’t hunt, that’s probably the end of you.

You don’t want to tackle an adult Triceratops that weighs the same as you, has 1- to 1.5-meter-long horns on its head, and is potentially pretty aggressive. Then even the big hadrosaurs—the classic duck-billed dinosaurs—weren’t present with any obvious defenses. They didn’t have armor, horns, spikes, or anything like that, but they were simply massive.

Yes, T. rex had the teeth and the bite, and even if its hand claws were a bit rubbish, just grappling with another animal that was the same size as it carried a risk. You could get a foot trodden on, or it could get off some kind of body slam or whatever. Even if you did bring it down, you’re never going to eat it.

If you bring down an animal that weighs 5 tons, it’s nearly your own mass. You’re not going to eat it before it goes rotten. That’s a huge amount of—not wasted energy, exactly, but you’ve probably put a lot of effort into this, and you’re not getting that much reward out of it.

Again, there are exceptions. Lynx are the classic one. Lynx are not very big cats, and yet they’ll hunt adult deer that are way bigger than them. Lions hunt things like buffalo, but they’re operating in a group, so it’s a bit of a cheat. There are some things that do this, but fundamentally, the vast majority of carnivores tackle stuff that’s way, way smaller than them, and that’s what we see.

Every record we have of basically any large carnivorous dinosaur where we have stomach contents, or evidence that it consumed something, or healed bite marks, shows this. We have quite a few. There’s a handful of cases where there’s obvious damage to a bone, and in more than a couple of cases there’s a tooth broken off in the bone, and then the bone has healed over it, so you know the prey got away.

They’re juveniles. They’re relatively young animals. That’s what they’re targeting. It makes ecological sense. It’s what modern animals do for very good reason.

Juveniles are relatively small and weak. They don’t have the horns, frills, armor, shields, and other defenses. They’re naive. They often have to learn what predators are, how to avoid them, how to check the wind, or even physically see them before they know that they’re a threat. They may have to see them kill something else before they know that they’re dangerous.

Juveniles forage badly. They’re relatively inefficient, so they actually need to eat more for their size than an adult does. On top of that, they’re not very experienced at foraging in the right areas. Even if they can find a good patch, the adults will often beat them up and chase them off.

Lex Fridman

You’re talking about juveniles across various species?

David Hone

Everything. This is just a universal pattern of being a smaller animal versus a larger one, or a younger animal versus a larger one.

Lex Fridman

So hunting young—

David Hone

Young things.

Lex Fridman

—young things is easier.

David Hone

Yeah, because—

Lex Fridman

Because they’re dumb.

David Hone

Right. They’re dumb, but they’re inexperienced.

Lex Fridman

Inexperienced.

David Hone

But they’re often feeding in suboptimal areas. This is the place with all the best food, but the adults will kick you off, so now you have to feed somewhere else. Maybe the food isn’t as good, in which case you need to eat more of it, so it takes longer. Or maybe it’s the area next to the edge of the forest where the T. rexes hide.

Either way, you’re stuck there, and then you don’t really know what you’re looking for and you haven’t got the armor, so guess who’s getting eaten? Again, there are lots of exceptions. You can’t have nature without things like that. But this is the absolute rule of thumb for how foraging, growth, and predation operate across everything from fish to starfish—fish as predators, starfish, praying mantises—all the way up to things like big cats, via animals like crocodiles.

That’s how it works, so it would be very weird if it didn’t also operate for dinosaurs. As I say, we’ve actually got direct evidence for this from bite marks and stomach contents. They’re taking small stuff.

Lex Fridman

Bite marks give a lot of information. That’s a powerful signal in paleontology.

David Hone

Yeah, absolutely. I’ve done quite a lot of work on it, and they can tell you an awful lot if you have the right understanding of the burial conditions. A weird thing that I think a lot of people don’t appreciate is that you basically can’t take fossils at face value, particularly when you’re trying to get into things like behavior and ecology.

Between the animal dying and the paleontologist digging it up, potentially quite a lot has happened. That’s where it’s really easy to start misinterpreting things. I had one like this not too long ago where I was an editor on a paper, and the authors had done a pretty good job, to be fair, but it was a discussion of whether or not several animals were together at the time of their death.

So, multiple theropods together in this quarry—and it's like, right, but there was loads of debris. You had loads of things like fish scales and other small bones. It's like, okay, but this looks like these animals potentially died somewhere else, and then a flood or a river washed them into this bay or a channel, or the water level dropped and they ended up together. But that doesn't necessarily mean they were together when they died. Just because you've got 3 animals together, what is potentially the story of how they got there?

Lex Fridman

So you have to consider multiple explanations and then try to figure out what is the most likely.

David Hone

Yeah, or what can you test with various bits of evidence? So there were some tyrannosaur-inflicted bite marks on a duckbill from Mongolia that I worked on years ago. The specimen was from Mongolia, but it was held in Japan, in a Japanese museum. I was working with the Japanese on it. I'm not a taphonomist—I'm not an expert in the study of decay and the history of specimens. I am in no way, shape, or form a geologist. I did zoology for my degree, but the guys I was working with were really hot on erosion and damage, and they were looking at some of the ways the bones had been damaged. They said, "Okay, we're pretty confident that the bite marks are sitting on top of erosion."

Lex Fridman

What does that mean?

David Hone

It means that the animal had died and was found in sand, in what would have been a river channel. This animal had died, washed downstream, and ended up on a sandbank. The sand is whipping past, because I've been in a sandstorm in China. It is not fun, and that's starting to etch some of the bones and damage them.

Lex Fridman

And after that, there's a bite mark?

David Hone

After that, you're getting bite marks coming in. That can only be scavenging. That thing had been dead and sitting out for days, possibly weeks, before something came along and chewed on it.

Lex Fridman

Wow.

David Hone

It pretty much can't have happened any other way.

Lex Fridman

And you have to take these really subtle signals to reconstruct the story.

David Hone

Yeah. But then you can start piecing some other stuff together. In this case, the skeleton is pristine. It's one of the best hadrosaur skeletons out there. It's certainly the best from Mongolia I've ever seen. All the bite marks are on one bone: the humerus, the upper arm bone. We went over the rest of the skeleton—nothing. The humerus is chewed to bits. There are bites all over it, but when you look, there are 2 really distinctive patterns.

There are deep, circular punctures. Remember what the shape of this thing looks like at the ends. Then, along the deltopectoral crest—it's much, much bigger in a hadrosaur, but this bit, remember, that's where all the big muscles attach—there are all of these types of close, parallel scratches. This is from a different bone and a different animal, but all these types of close, parallel scratches.

That looks like selective feeding, because it's using its giant, crunchy teeth at the ends to get the bone off. This is off a buried skeleton. T. rex has really small teeth at the front of its mouth, right in the front where our incisors are. They're called incisiform teeth. They look like incisors. They're a fraction of the size of the big ones, and they've got a really weird, flat back. That's what these are. It's hitting this with the front of the mouth and pulling.

Lex Fridman

And that's mostly for eating?

David Hone

Yeah, and that's why it's just on the deltopectoral crest, because that's where all the muscles are. I always liken it to getting something like an Oreo: you take the top off and then scrape the cream out with your teeth. I think most people have done that. That's what it's doing. It's got this little row of teeth, and everywhere you get lots of muscle, you get little rows of teeth together, pulling.

Lex Fridman

So there's different bite marks for sorting, fighting, killing, and then there's different bite marks for eating.

David Hone

Yeah, so it kills and dismembers with the big teeth up the side, and then it feeds with the little front teeth.

Lex Fridman

And all of that has evidence in the bones? What hunting strategy does it use? Can we figure that out?

David Hone

That comes down to that foot stuff. They're relatively efficient compared to a lot of other things, and particularly compared to the herbivores. That means they're probably looking at long distance rather than speed, and that makes sense because, even though the kind of stuff we're talking about—like I said, maybe they get into 20–25 miles per hour—that's pretty quick, but some of the smaller stuff is going to be a lot faster than that. Remember, that's a real upper estimate. They're probably not that quick.

Lex Fridman

They're just jogging after you.

David Hone

Right, but they've got the distance. It's much more of a hyena- or wolf-like strategy than a cheetah going for hyperspeed, or a lion going for a relatively quick burst: it either gets you or it doesn't.

People then just go, "But that's ridiculous. They're not even that quick." It's like, yeah, but if you're hunting something big that's not that quick either, that's a misconception. When I'm talking about juvenile dinosaurs, I don't mean just out of the egg and weighing 1 kilogram. A juvenile Triceratops can still weigh a ton and be the size of a rhino. They're not that fast. Again, if you get a head start on them because, as I said, I suspect they're nocturnal, that's the other thing: it's really hard to hide a T. rex. Even lions and tigers struggle to hide in long grass. When you're 3.5–4 meters tall, you can't hide. Maybe in a forest, but even then, you're probably going to stick out, and it's going to be hard to maneuver between the trees.

We've got big tyrannosaurs living in what we know to have been relatively open environments. Maybe there are some stands of trees, but it's not a woodland or a forest or anything like that. They're living in the open and surviving in the open, so they've got to have a way of doing this. I think it's some combination of being nocturnal—so it's relatively easy to "sneak"—and then just running things down. "Sneak" isn't quite the right word, but you can approach things to cut the distance down for your initial strike.

Maybe a 1-ton Triceratops or a 1-ton hadrosaur is rather faster than you, but if you've covered the first couple of hundred meters to get up to your top speed before they start running, then you're probably much closer to them. Will they exhaust faster than you'll keep going? Probably not 100% of the time. No predator's that effective. But I suspect that's what they're doing, and it fits with what we know of their size and their vision. They have a very good sense of smell. Again, that makes sense at night. It makes less sense if you're diurnal and operating primarily in the day. You've got to hide this thing, and we know they're pretty efficient versus relatively fast but not that efficient prey.

Lex Fridman

Well, there's a bit of a debate of scavenger versus hunter.

David Hone

They're obviously both, because we've got things like the bite marks I just described, which is pretty much definitive scavenging. Then we've got the healed bite marks with T. rex teeth buried in bones, which is pretty much definitive active predation. So we've got evidence of it doing both.

Lex Fridman

But can we possibly figure out what was the primary strategy?

David Hone

That gets much harder. My guess is they're probably still primarily actively carnivorous. If you look at stuff that's reliant on being a scavenger, the true scavengers, like the vultures and condors, have to be ultra-long-distance, very energy-efficient travelers. They're soaring in thermals. They're barely using any energy to fly.

Lex Fridman

How far were they spread? Where did they live?

David Hone

The ones we've found, you've got them from Alberta down to probably New Mexico. There are some tyrannosaurine teeth—so, very close to T. rex—that may or may not be T. rex in New Mexico. There are similar teeth in Mexico proper, down in Coahuila, so about halfway down Mexico.

Lex Fridman

Mongolia also, or no?

David Hone

In Mongolia, you have a thing called Tarbosaurus, which is a very, very close relative of T. rex. It's the nearest genus that we have. But T. rex probably occupied almost all of western North America. At times, the east was split off and separate.

Lex Fridman

But the entire surface of Earth had dinosaurs on it. Well, most of it.

David Hone

Yeah, we've got them in Antarctica. We've got them in Antarctica even close to the mass extinction event.

Lex Fridman

Just an insane number of dinosaur species all over the Earth, just the same kind of variety we have in the animal kingdom today, you just have in the dinosaurs.

David Hone

I mean, how many dinosaur species were there? I basically wrote an entire book chapter about this because there are so many. This would make the number high, and this would make the number lower. There are counterarguments to both, so you can guesstimate almost any number and probably be very accurate or very far out.

Lex Fridman

Yeah, but we should say that a large number of dinosaur species are constantly being discovered.

David Hone

Yeah, so we've named, give or take, in the realm of 1,500–1,600 valid species. Not everyone agrees on every species, but most people would be satisfied with that number. We also name in the realm of 40–50 a year, and we've been doing that for at least the last 10–12 years. That number is rocketing up. It shows no signs of slowing down.

We still haven't really explored India very much. We're starting to find entirely new beds in places like Ecuador.

Lex Fridman

Argentina, we know, has a ton of stuff, but we've never excavated there very much. Australia, we know there's a ton of stuff, and we haven't excavated there very much. So there's lots of places, even now, to still go through.

This is a good moment to take a brief tangent and look at paleontology. How do we find these fossils? What's the magic? What's the science? The art?

David Hone

The same way, more or less, that people did in the 1750s, or whenever you first started getting them. For dinosaurs in particular, but this is true of the vast majority of stuff, there are essentially 2 ways of doing it.

The simple one is where you have quarries of particularly fine things like lithographic limestone, or printing limestone, or stuff that's very similar to that. Sometimes it's volcanic. You get these super, super fine layers of sedimentation, and that's where you get these places of exceptional preservation.

Whenever you see feathers, or almost-feathers, almost always, whenever you see feathered dinosaurs, it's like, “Oh, we got the skin, we got the claws,” and the whole skeleton's laid out. Archaeopteryx, being the first bird, is an absolute classic example. It's from these beds. You find them by basically splitting limestone.

We don't usually dig for them. It's because there are quarry workers and people who are already doing this because the stone is useful, because there might be 1 decent fossil for every few hundred tons of rock you shift. In which case, you could get every paleontologist in the world there for a couple of years, and you wouldn't find very much. You rely on the fact that hundreds of guys are doing this constantly, and then sooner or later they'll find something, and then you've got it. That's the super-easy way.

The only slightly more complicated way is you go to somewhere where, geologically, we know it's the right age and it's the right kind of rock, and ideally fossils have been reported from there before. Geologists mapped all the world's geology years ago in quite a lot of detail. There are gaps, there are places where we don't have the details, but in general, we know. Then you go there, walk around, and look. That's basically it.

Lex Fridman

You're looking for something that's sticking out of the rock.

David Hone

Yeah. You always get this constant—and I think borderline myth—of the idea that dinosaurs and mammoths and lots of other fossil things entered lots of Indigenous cultures because it's impossible that people were wandering around, say, Dakota, and the Native Americans didn't come across some dinosaur fossils.

I'd agree with that. It's pretty much impossible they didn't come across some dinosaur fossils. Did they come across a whole skeleton laid out on the ground? No, because those don't usually exist. Even if they're tougher—or it doesn't matter if they're tougher or weaker than the surrounding rock—dinosaur bones are, in some way, shape, or form, lithified. They turn to rock, and they will absorb some of the minerals from whatever they've been buried in.

Even in places like Mongolia and northern China, where I've been, where the fossil bone is actually quite a lot tougher than the sandstone that it's embedded in, you can find a bit of bone and pull it out, almost rub it with your hands, and the sand comes off, and there's your bone. They will decay pretty quickly. Sandstorms—sand just etches stuff. The tiniest bit of moisture, particularly in winter, gets into the cracks. Bones are incredibly porous. That freezes, expands, cracks, and the bones just shatter.

You find shattered bone on the surface everywhere. What you rarely find is a decent bone on the surface, let alone a skeleton.

Lex Fridman

So there has to be something that's sticking out just a tiny bit—

David Hone

So that you can see it, but it's still buried. Right. And it happens. The greatest one that I saw—or that I didn't see—happened with a friend of mine when we were in northern China. He went, “Yeah, I can see a bit of a claw sticking out of a hill.” It was this much. You could see less than a centimeter coming out of a hillside.

Lex Fridman

That's the dream, right?

David Hone

Dig a little bit, and there's a little bit more. Dig a little bit, and there's a little bit more.

The system we were running there was that some guys were searchers and some guys were diggers. He and I were searchers. We were told, “Okay, you guys have...” He found it. “You found something; go and look for something else. We'll dig it out.”

We came back a couple of days later and checked in on the digging team. “So what is it, then?” “Oh, it's a complete skeleton.” It was a very, very close relative of Velociraptor. We ended up naming it Linheraptor, so “the raptor from Linhe,” which was the nearest town.

The legs were a little messed up because water had got to them, and the end of the tail was missing, but that was about it. It was a 90-plus-percent-complete skeleton, and it had been found with 5 millimeters—a couple of sixteenths of an inch—of bone sticking out of a hill. That's what you want, because every so often, behind that is a whole skeleton. If you're looking for skeletons on the surface, they're going to be gone before you get to them.

Lex Fridman

When it's a near-complete skeleton, you did a show, Terrible Lizards, on Stan.

David Hone

Oh, yeah.

Lex Fridman

The T. rex fossil that sold for $31.8 million.

David Hone

I've seen some of them.

Lex Fridman

That's a nice, big adult T. rex. Looking at a fossil like this—for $31.8 million—what's the excavation process when you have a claw sticking out, like you were mentioning, and you're getting that whole thing out without damaging the bones? What can you say about that process?

David Hone

It depends where you are. It depends how many people you've got. It depends on your budget, and it really depends on the rock.

Again, going into China or Mongolia, where this little guy's from, the bone tends to be relatively strong compared to the sandstone that it's in. That means that, first, it's fairly tough and resistant, but it also means that it's really easy to dig. I've dug stuff by almost pulling it with my hands or getting my fingers in. If you get something like a chisel or a hammer, you can just cruise through this rock.

Lex Fridman

But you have to be really careful not to touch the bone, I guess?

David Hone

It depends how strong it is. Some bone is incredibly strong; some isn't, because they've all fossilized differently. What we're usually doing is applying glue to it, though. There's this wonderful stuff called Paraloid, and it's a special glue for fossils. As I said, bone's super porous, so it's really good at sucking up liquids.

Lex Fridman

So you're basically filling it with glue so it makes it stronger?

David Hone

Yeah. Paraloid's really great because you can dissolve it with acetone, and it basically doesn't react with anything. You can fill your fossil with glue, but then, if you want to take all that glue out, you can pretty much just dissolve the glue back out again.

Lex Fridman

Very cool.

David Hone

What you would normally do is, for something in China, where the rock is relatively soft and the bone's relatively tough, and where we don't have any manpower and shipping problems—which is a real issue in other places—you basically map out where you think the skeleton's going.

In the same way that you can imagine a cake, and someone said, “Put a toy dinosaur in there,” and you've got to find it without damaging it, you'd stick your finger in the cake and just dig until you hit the edge of it. Then you go in somewhere else, and keep going in. That's what we're doing. We're just going in from all sides.

Once you've hit 3 or 4 bones, you know which way it's going into the hillside, usually. Sometimes they're very weird and mixed up. Then you can almost trace the outline of it, and you'll just dig all the way around that. That might involve taking the top off a mountain, depending on where you are. In the desert, it tends to be a bit easier.

We've had stuff where the first 3 days were just 10 people with pickaxes digging a hole to get down to the right level.

Lex Fridman

Sometimes the excavation requires large equipment, right?

David Hone

Yeah, we've used jackhammers and stuff. We've used a backhoe, and we've literally driven it into the desert and just dug a big hole next to the fossil.

Then there's the classic thing of covering it in a plaster-of-Paris jacket: strips of burlap sacking, plaster of Paris, and some water; wooden beams if you want to make something really big and really solid; and just basically wrap it all up and then take it out. Again, that's what they were doing 150 or 200 years ago. That hasn't changed.

Where it gets more complicated is if you've got really hard rock that's very hard to get through, particularly if the bone is fragile. Then it becomes difficult, because if you want to get a jackhammer in, the vibrations mean you're going to shatter your bones before you've even cut through the rock. So then you might be down to doing it manually.

Lex Fridman

And manual is—

David Hone

Hand-chipping it out.

The other way you end up with that is the classic Jurassic Park thing. Was it the second scene where they're digging in the desert and there's the whole skeleton laid out, with 5 or 6 guys all digging around it and exposing it? That's actually quite common in the States. The reason is that huge amounts of those excavations are being done on government land, national parks or whatever, or protected land.

And very often, the rules are: you're not allowed wheeled vehicles—full stop—at all, to protect the environment. You can walk in and walk out, but you can't drive. When we're in the desert in Mongolia or in China and we're allowed to do this, my boss literally drove into town, hired a guy with a JCB, and the guy drove out, picked it up with a bucket, drove it back into town, put it on the back of a flatbed, and we drove it to Beijing.

If you're out in a protected area and you can't, you've got 2 choices. You can take it out by hand, but that means it's got to be light enough that half a dozen people can lift it. If it's a block of stone the size of this desk—a couple of meters by a couple of meters by a meter high—that's basically impossible. So that means you've either got to carve chunks off: take the head off, take the arm off, and whatever, and you can get it out that way, but it's not ideal.

There's always the risk of breaking it, and you're losing some information. If you want to make a really spectacular display, you don't want to join through every big bit of bone. You want to show the public one piece. So the alternative is to get rid of every bit of rock you possibly can to make it light enough to helicopter it out.

Lex Fridman

Wow.

David Hone

And so normally—so in China, if we hit that bit of bone going in, we're just going in around the sides until we've hit it. Take the top off, take the bottom off, and just take it out so the skeleton is completely encased in rock and it's as safe and secure as it can be. Then we'll do the preparation work back at the lab.

Lex Fridman

That's heavy, though.

David Hone

If you're going to have to lift it with a helicopter and they've got a weight limit of only a couple of tons, then you need to pay twice as much for a more expensive helicopter. So you take off every gram of rock that you think you can to get the weight down so you can ship it. It varies massively. Something the size of Stan—that's months of work. You're probably doing that across 3 or 4 years with a team of half a dozen people.

Lex Fridman

So can we just talk through, using Stan as a case study? Stan was first discovered in the spring of 1987 by amateur paleontologist Stan Skekanson in the Hell Creek Formation near Buffalo, South Dakota.

David Hone

Yeah. But it was the Larson brothers from the Black Hills Institute who dug it up. They're a commercial outfit, so they dig stuff up to sell it. But they also make casts and sell them. I do have a cast of one of Stan's teeth.

Lex Fridman

Oh.

David Hone

You can buy casts of Stan's teeth. You could buy casts of the head. You could buy the whole skeleton.

Lex Fridman

So it's a famous skeleton.

David Hone

You see Stan in a whole bunch of different places. There's a Stan just up the road from here at Oxford. Oxford's got a cast of Stan. I was just at Lyme Regis, the famous fossil locality in the south of the UK, a couple weeks ago. One of the fossil stores has a skull of Stan in the window. Stan turns up again and again and again.

Lex Fridman

So the process, as written here, involved removing the overlying rock using heavy equipment like a Bobcat.

David Hone

Yeah, so we call that the overburden: all the rock that's sitting above the layer with our fossil in it. When you're lucky, that's a foot of sandstone, and you shovel it out in an hour. I've seen guys in South America do this. There was a team in Argentina—I think my old boss, Ollie Rowhurst, showed me this—and they took 20 or 30 feet off the top of a hill to get down to this fossil. It was probably half an acre in size, with 20 or 30 feet of rock.

Lex Fridman

This is incredible. I wonder if you could speak to some of these other components: carefully extracting each fossil bone by hand with picks and brushes; plotting and diagramming the bones; using a grid system at the dig site; wrapping the bones in burlap and plaster for safe transport to the BHI lab. Some of this stuff you've spoken to. What's with the diagramming? What's with the plotting and the diagramming?

David Hone

So you may well have seen something like this on archaeology shows or something like that. Nowadays, tech's getting better. People are using drones and stuff for this, or taking hundreds of photos and then building photogrammetry models. You just get a 3D model in the computer.

Lex Fridman

Or just modeling what we're looking at here?

David Hone

Yeah, but it shows where you found everything. It goes back to that stuff we were saying about the process of fossilization, or the process of what's happened to that animal from death to discovery. A classic thing is bones being in a line. You can imagine that bones are lots of weird shapes, but certainly lots of bones—ribs, arms, and legs, things like this—are quite long bones. So if they're in a current, they will tend to spin on their axis so that they are facing the current.

If you're finding all the bones are in a line, that probably tells you that this thing has had quite a lot of water washing over it. You're then probably going to be missing most of the small bones because the big, heavy bones won't be shifted by that current, but maybe the small ones will.

Lex Fridman

Mm-hmm. Got it.

David Hone

So it might tell you where to go and dig further down the hill, quite literally, but it can also just tell you, "Okay, this thing—there's no way this thing died here. It absolutely got moved, so we need to factor that in when we're trying to interpret it."

Lex Fridman

Okay.

David Hone

Or we've got this one weird bone and we can't work out what on earth it is. Well, maybe it's from something else, because if we know a whole bunch of stuff washed together, maybe that's a random bone from a different animal.

Lex Fridman

Yeah. Maybe that was eaten, or there might be a different story if it was washed like you were describing.

David Hone

Any of that kind of thing. So that's where you want to have as much information as possible.

Lex Fridman

It says here, "Once at the lab, the bones underwent more than 30,000 hours of cleaning, preservation, restoration, and documentation." Stan's skeleton is notable for its high degree of completeness—about 70% by bulk, 63% by bone count—and the exceptional preservation of its skull, which has become a scientific standard for the species.

David Hone

Yeah. So there's this unbelievably beautiful skeleton, Borealopelta. This is a helicopter lift. Absolutely.

Lex Fridman

It's awesome.

David Hone

Phenomenal preservation from northern Alberta.

Lex Fridman

What?

David Hone

Its full name is Borealopelta markmitchelli, and it's called markmitchelli because it was named after Mark Mitchell, the preparator, who basically spent, I think, the thick end of 2 years on this. This was his job. He did other stuff as well—he's doing some other preparation, he's doing some fieldwork—but Mark basically went in every day, 9 to 5, cleaning the rock because the rock was hard and the bone was soft, and it's extraordinarily well-preserved.

Lex Fridman

Borealopelta is a genus of plant-eating armored dinosaur. It sure as hell looks armored. This is an incredibly preserved specimen.

David Hone

Yeah.

Lex Fridman

From the Early Cretaceous period, about 112 million years ago, found in what is now Alberta, Canada. Amazing.

David Hone

Yeah.

Lex Fridman

Look at this thing.

David Hone

So Borealopelta is one of the ones where we've even got some of the evidence of patterning, and it suggests that it's darker on top and lighter underneath. This illustration—I think Julius Chattoni did that. He's a Canadian paleoartist, and so that color pattern is roughly accurate.

Lex Fridman

Oh, wow. So this is true to color?

David Hone

Well, give or take some very large uncertainties, it's going to be something like this.

Lex Fridman

Look at this thing.

David Hone

So these guys are nearly armored pine cones.

Lex Fridman

That's hard to eat, that thing.

David Hone

Yeah. Though it's very much the adult condition. The juveniles seem to be far less armored, if not unarmored.

Lex Fridman

We're back to the juveniles thing.

David Hone

Right. But that's why we— That armor is absolutely going to be effective as antipredator armor, but it's probably evolved primarily for combat and display between members of the species, because otherwise, if it stopped you being eaten, the babies would have it.

Lex Fridman

This fossil is considered one of the best-preserved dinosaur specimens ever found, with armor, skin, keratin sheaths, and even stomach contents all intact. Incredible. And for that, he really did the work.

David Hone

It was also found miles and miles and miles out to sea—or the paleo-sea. This is from a site which normally gives us big marine reptiles: predatory plesiosaurs, ichthyosaurs, and then mosasaurs and stuff like that. And then it turned up an ankylosaur—well, a nodosaur in this case.

Lex Fridman

Yeah. Wow. This is incredible. So, okay, let's complete the journey of Stan to the museum. You get to the process of cleaning everything, stitching it all together.

David Hone

Like Mark suggested, even with an animal that size—Borealopelta is 4 or 5 meters long—we've only got the front two-thirds of it. This can be needle-level stuff.

Lex Fridman

That's how you get to the 30,000 hours.

David Hone

Yeah, exactly that, if it's that quality and you want to get everything open. Something like Stan has a really complicated skull. The skull's full of lots of little bones, and the bones are really fragile, so that just adds to the time.

At least with the ankylosaurids, the skull is just this giant solid block of bone, which makes life a little bit easier. So, yeah, they're going to put those hours in, and that's really going to help them sell the animal, which is ultimately what happened. Stan sat in the Black Hills Institute for decades. They discovered it in 1987, and they sold it in 2020, so they had it for 30 years sitting in their kind of little museum.

Lex Fridman

And then my understanding was basically that the brothers broke the company up, and that's why they sold it.

David Hone

Yeah. But it was still incredibly surprising that it was sold for $31 million.

Lex Fridman

Yeah, far more than I think anyone thought it was going to.

David Hone

Well, if you're not buying teeth or an ammonite in some small fossil shop, when you're talking about things like whole dinosaurs and whole tyrannosaurs, I think it's a bit like the art market: it's worth what people will pay for it.

Lex Fridman

Plenty of T. rexes had sold for a few million dollars, and therefore everyone thought it might be $5 million. $10 million would be an absurd sum of money. And then it went for $30 million, and it's like, "Okay, well..."

David Hone

Two.

Lex Fridman

I was going to say, someone wanted it that badly, but clearly not 2 people wanted it that badly, because if only 1 guy is prepared to bid $30 million, then it goes for a million more than the next-highest bidder. But presumably 2 people, if not 3, bid it to get that high.

David Hone

Yeah, it was anonymous at the time, but Abu Dhabi's Department of Culture and Tourism has since come out and said they were the ones.

Lex Fridman

I know they've got it.

David Hone

And that record has since been beaten, apparently, by—

Lex Fridman

Apex, the Stegosaurus, which I still haven't seen, though a friend of mine has sent me some photos of this thing. Is it impressive to you, this thing?

David Hone

No, not especially. That's why I can't imagine that it sold for that much. It's a really nice Stegosaurus. It's a pretty big Stegosaurus.

Lex Fridman

Well preserved.

David Hone

I've seen other very good Stegosauruses, and I don't understand why that's worth that much more than something like Stan. But it shows you the market.

So, we're here in London. There's a Stegosaurus called Sophie in the Natural History Museum in London. Sophie is a young animal, so she's not very big. I mean, it's a sizable specimen. I'd say 5-ish, 6 meters, off the top of my head, total length. But Sophie's truly exceptional. There's a couple of plates missing, a handful of ribs, a couple of bones in the tail, and I think a couple of toe bones. This is, by far, the most complete Stegosaurus out there.

Lex Fridman

Wow.

David Hone

That sold for, I think, 250,000 pounds, so maybe $400,000, about a decade ago. So this has now gone up 100-fold for an animal which is quite a bit bigger but is way less complete. For me, those 2 things kind of balance out, because size is always impressive, and that's what the public likes, but also a complete one is better than half of one or two-thirds of one.

Lex Fridman

So how has the price gone up 100 times, or from $400,000 to $40,000,000 in 10 years, for roughly the same thing?

David Hone

A T. rex is a little bit more epic than—

Lex Fridman

Well, that's the thing.

David Hone

—a Stegosaurus.

Lex Fridman

T. rex has a massive premium on it. A Stegosaurus is one of those top-tier—you can virtually do the list. T. rex, Triceratops, Diplodocus, Brontosaurus, Stegosaurus. It's in that first 6 or 7. These days, Velociraptor, thanks to Jurassic Park.

There's the list of 7 or 8 things that any random human who doesn't care about dinosaurs and doesn't know anything about dinosaurs has probably heard of. They'd have an idea of what it looked like. "Oh yeah, it's got the big stuff stuck along the back." You'd get that answer from almost any—99% of people on the street. But yeah, it's not a T. rex.

So how is it worth 50% more, and it's not even a particularly complete skeleton, to my understanding? I don't get it.

Actually, since we're on the topic of money, if I gave you, let's say, $10 billion, how would you spend it? I'd force you to spend it on dinosaur-related things. How would you spend it?

David Hone

I mean, I'd probably drop half a billion or so on the best museum you'd ever seen.

Lex Fridman

So, put together a museum. You're one of the great communicators, one of the great scientists, and so you would want to push forward the whole field.

David Hone

Yeah.

Lex Fridman

And one of the ways to do that is a great museum, actually.

David Hone

Yeah, but it's twofold. There's the communication and the education part of it, which I'm massive on, and I think research is pointless if you don't communicate it at some level. I'm not saying everyone needs to communicate everything. If you're working on the nuances of a calculation of the volume of a black hole or something, it probably doesn't need a press release or a new museum exhibition. But fundamentally, we should be talking about our work.

Also, you've got to store this stuff. Many fossils are fragile. They need to be kept, not necessarily in climate control, but at least you want a basement that is much more even than just sticking it in a box in a warehouse somewhere. So you've got to be able to store this stuff to be able to study it, or it's kind of pointless.

With the rest of that money, I'd buy a ton of land, like the quarries that gave us Archaeopteryx in Bavaria and have given us a ton of other stuff. I've worked on a load of pterosaurs, the flying reptiles from there. This stuff is mostly commercially run, or just straight-up privately owned and not being commercially run. Someone's just inherited it and is sitting on this stuff.

Lex Fridman

So if somebody's building stuff on land, does that threaten the possibility of discovering something on it?

David Hone

It's more that they're not necessarily exploiting it with fossils in mind.

Lex Fridman

I presume you have to balance the search efforts and the land.

David Hone

Yeah, but $1 billion on its own would go a very, very long way—almost infinitely—if you're just creaming off the interest and then funding excavations and supporting scientists who are already embedded in other museums, universities, or other research institutes.

Lex Fridman

So the rest is for buying up land so that those people can do their work.

David Hone

Yeah, you look at somewhere like Brazil, and there's—I can never remember the name of it—but there's, again, one of these zones of exceptional preservation where superlative pterosaurs, fish, a handful of dinosaurs, and a whole bunch of other stuff have come out. It's just a giant commercial mining operation.

When they think they're close to a fossil, they stop and pull it out, and they'll send it to a museum. More often, they'll sell it to a museum, and museums only have so much money. Whereas what if I owned that quarry, made sure everyone who worked there was trained, gave them a bonus every time they found anything, and then just handed everything they dug up straight into a museum?

Lex Fridman

So there would be some element of crowdsourced paleontology?

David Hone

Yeah, but it's more that no researcher ever needs to spend money to access that. No museum needs to go and find a new donor to give them half a million to go and buy this one specimen, knowing that it might still go to some Silicon Valley billionaire's foyer or whatever. It's like, "Well, I own the land, so it's mine. Problem solved." That's what's in my head.

Lex Fridman

It just would be wonderful to scale up the effort to where we can map out the whole story of this time, because it's such a fascinating time in the history of Earth.

David Hone

I've jokingly written a couple of times about how all science funding in the world should go to paleontology. The idea being that if you want to investigate black holes or neutrinos or chemical crystallography or panda genetics or whatever it is, you can do that any time you want. That's not going to change a million years from now as it will from tomorrow.

But fossils are in places that erode, and if we don't dig them up, they're gone. So we should dig all the fossils up now, and then we've got forever to study them. But if we don't dig them up now, who knows? Maybe there's something twice the size of T. rex, and it sat on a hillside for 6 months. Then the wind got to it, and it's gone. That was the only one that ever preserved. Well, we'll never know now.

To be clear, this is a joke. I'm not suggesting we should stop doing cancer research, physics, and other things, but we're in a fundamentally different field where our science is literally disappearing.

Lex Fridman

Yeah. I mean, I know it's a joke, but there's some truth to it. On the flip side, one of the hopes is that technology will somehow ease the search and discovery process, but as you said, so far most of it—

David Hone

It hasn't.

Lex Fridman

So far.

David Hone

Yeah. Jurassic Park, '93: you've got that little scene where they've got the thumper or something they call it, and it hits the ground with seismic, and then they go, "Look, look! Here's the whole skeleton." They tried it. It doesn't really work.

We've tried looking for stuff with drones. That helps you get into some inaccessible areas, but until the resolution is probably better, you've still got that problem of looking with human eyes, which are binocular, and being able to just tilt your head completely changes how you see something in a way that flying over just won't.

I know they've tried looking—because the bones are porous, they tend to suck things up, so actually dinosaur bones can be really radioactive if they're in areas where there are things like uranium. There are drawers which have lead boxes around them and stuff like this for dinosaur bones, or just signs saying, "Do not handle." They're very low-level radioactive. You'd have to stick it in your pocket for 6 months to run any real risk, but they're radioactive, much more so than the background.

So can we do that? Hmm, turns out, not really. So again, maybe technology will advance.

Lex Fridman

Humans are quite incredible.

David Hone

Yeah, we are. But also, paleo's kind of at the bottom of the pile, you know.

There aren't many of us. We don't have a lot of funding. It takes real money to adapt stuff. We're scanning stuff with MRIs and things like that in hospitals, but it mostly doesn't work very well because the problem you've got is, as I said, the bones take on some of the properties of the minerals in which they're embedded. That means their density is really similar, and things like MRIs or seismic activity are basically looking for differences in density.

If it's the same density as the surrounding material, it's like I put some green plasticine in some blue plasticine: there's going to be a bit of a join, and they're going to be very, very slightly different. But ultimately, you're not going to be able to detect that through most means if you're looking for density or mass or anything like that.

Lex Fridman

Personally, I think there are few things as important to understand as the history of life on Earth. There are books, right? Or maybe you could think of it as chapters, and one of the chapters is the time of the dinosaurs. Then there's a great extinction, so it just goes up and up.

David Hone

I mean, that's not a million miles off. I think Darwin had an analogy like that: we've got a few words on a few pages spread out, but between them you get an idea of what the story is and where it's going.

Lex Fridman

I think what humans don't quite realize is we may end up being just a chapter in a book. It might be our extinction event, self-created—perhaps a nuclear war, perhaps robots take over. Perhaps we don't know.

David Hone

Well, or dumb luck. The dinosaurs were doing absolutely fine until a dirty great rock hit them. You can't, Ben Affleck and Bruce Willis movies aside, do much about that.

Lex Fridman

Hey, you take that back. There's nothing they can do wrong.

All right. Quick pause. Bathroom break? We've taken a few tangents, but let's continue on the thread of T. rex. Go to the skull. The skull of T. rex is iconic. You describe it as being incredibly robust and overbuilt.

David Hone

Yeah. There's a lot of bone on there. We mentioned a couple of other things, like Giganotosaurus, this giant carnivore.

Lex Fridman

That's the one.

David Hone

Yeah, that's from my old blog. It's not my image.

Lex Fridman

What are we looking at, on the left and the right?

David Hone

You've got T. rex on the left, in orange, and Giganotosaurus on the right, in red. As I said, they're pretty similarly sized, but just look at the robusticity. The front of the snout of T. rex is all bone, and yet the major openings—the antorbital fenestra, the opening in front of the orbit—is absolutely massive in Giganotosaurus. It's like half the skull.

The opening at the back of the skull is much bigger. The opening in the lower jaw is much bigger. Actually, the jaw, side to side, is much thinner. Their heads are the same size, and as animals, they are about the same linear dimensions, but you can just see there's way more bone in T. rex.

Lex Fridman

It's incredible.

David Hone

It's not overbuilt; it's obviously evolved so that this is the right amount of bone for the stresses and strains, for what it's doing and how it's acting. But you compare it to anything that's not a very large tyrannosaur, and suddenly you see just how much bone has gone into it.

It's an absolutely large head, but it's a very heavy head with a lot of bone. A lot of that bone is there to resist all the forces of all the muscles, because it has this giant, super-powerful bite. Again, you can see that in the teeth.

Lex Fridman

So the bone and the muscles kind of evolve together—

David Hone

Yeah, yeah.

Lex Fridman

—to get bigger and bigger and bigger and bigger. You need this kind of structure for the power that the crush has.

David Hone

One of the big things tyrannosaurs have—and this goes all the way down to the earliest tyrannosaurs—is fused nasals. The earliest tyrannosaurs were our size: little diddy things, 2 or 3 meters long and a meter and a half tall.

They're a pair of bones that, in us, don't amount to a lot, but obviously in something like a dog or a baboon with a long nose, they make up the whole top of the snout. There are 2, 1 on each side. In tyrannosaurs, they fuse together, so they form a solid bit of bone. The whole top of the nose is solid.

That makes the skull fundamentally more rigid and able to take more power through it. The very early ones weren't super-biters, I suspect, but they do also have the little flattened teeth at the front. I strongly suspect the fused nasals, at least originally, were for resisting that. If you've got a long nose and you're pulling with quite a lot of force at the very tip, that's going to bend your snout. So you strengthen that.

Lex Fridman

Can you speak to the evolution from the smaller to the bigger T. rex? What were some of the evolutionary pressures? What's the story of the evolution?

David Hone

Tyrannosaurs go back to the Middle Jurassic. Tyrannosaurs were around for 100 million years, from about 160-ish or 165-ish million years ago until the extinction—66.5, I think, is the current dating for that. So you've got 100 million years of them.

The Middle Jurassic, annoyingly, is probably the bit of the Mesozoic—the whole dinosaur period—that we know the least about. By chance, we don't have many rocks exposed of the right age that are fossil-bearing. But we've got 2 or 3 tyrannosaurs from that time.

They're really quite diddy. They'd be chest-high to us, 2 or 3 meters long, including the tail—probably more like 3, a lot of them. Little heads, long arms. They look like every other carnivore going. There's not a lot special about them at this point. They've only just separated from their nearest groups, which are actually something like the ancestors of Giganotosaurus.

They do have the fused nasals early on. They do have these special little teeth at the front of the jaw very early on. They're feathered early on, definitively. We have skeletons with feathers on them that are early tyrannosaurs, at least until the Early Cretaceous.

They're knocking around as relatively small animals in Europe and Asia. We have a couple from the UK. We have a whole bunch from China. There's stuff from Kyrgyzstan and places like this. I think there's one relatively early one from Russia.

When they get into the Early Cretaceous, they start getting quite a bit bigger. Someone like Yutyrannus—

Lex Fridman

There you go.

David Hone

Yutyrannus is fuzzy. We have 3 specimens definitively feathered. It gets to 6 or 7 meters long.

Lex Fridman

There's something funny-looking about the sexy, smaller, earlier version of the T. rex.

David Hone

But again, this is 7 or 8 meters, maybe weighs half a ton or a ton. We are very much on the menu for an animal that size. It's massive and dangerous.

Quite what triggered them is hard to say. There are general patterns in evolution of size change, and one famous one called Cope's Rule, which I've worked on a fair bit, is the idea that over time, things tend to get bigger. They do for various different reasons, one of which is almost like diffusion. If you start small and you evolve, you can't get much smaller, but you can always get bigger, so you'll naturally diffuse away. Whereas if you're a blue whale, you probably can't get much bigger, and its descendants will probably end up being smaller.

There are reasons that bigger things do better. You can hunt more stuff. You are more energy-efficient. You can move more efficiently. You're dominant in contests, particularly with conspecifics. If you're trying to win a territory or win mating rights, bigger things usually beat up smaller things. So there's going to be selection favoring them.

But then big things don't usually do well in extinction events, so that tends to reset the clock by killing off the big stuff, and then smaller stuff does better again.

Lex Fridman

So mostly, there are evolutionary advantages, but—

David Hone

But a fairly big one. It's the classic thing: there's a day-to-day advantage to being bigger, and that might last for a few million years, right up to the point that suddenly there's the biggest drought the Earth has encountered in 5 million years, and then all the big stuff just gets nailed.

Lex Fridman

We should probably say: is it accurate to say that the bigger you get, the fewer of you there are?

David Hone

There are, yeah. There's just less fundamental space. There's more mice than there are elephants. There are more elephants than there are whales. There's only so much biomass that an ecosystem can support.

Lex Fridman

And bigger things are just worse at repopulating in extinction events—

David Hone

Right, so they're less likely to survive because they need more fuel. What would feed a mouse for a year won't feed an elephant for a week. If there's an extinction event, the mice are going to have an easier time finding a few little seeds than an elephant is going to have finding tons of food.

Then they've got less genetic diversity. There might be 5,000 mice; there might be 200 elephants. So who's likely to have more genes, or who's likely to have selection acting on those genes to produce a survivor? The one with 5, 10, or 1,000 times the population.

On top of that, you've then got the very slow reproductive cycle, which again gives evolution not a lot to work with if, as an elephant, you're breeding once every 5 years, and as a mouse you're doing it once every 8 weeks.

Lex Fridman

What can we say about the evolution of just the massive bone-crushing power of—

David Hone

That starts kicking in seriously around Eotyrannosaurus and up. That's when you start getting not just bigger animals that are getting to a comparable size to the other big dinosaur carnivores of the time; you start getting those bigger heads.

But even then, relatively late in tyrannosaur evolution, getting into the middle part of the Late Cretaceous, you see a split, and we have a group called the Alioraminous, which have really, really long, thin skulls. They look much more like a giant Velociraptor-ish animal than a tyrannosaur.

Still relatively small arms, but it has a very long snout. This is a fast-biting animal with a relatively light bite, so it's probably taking really quite small stuff proportionally. On the other side, you've got the tyrannosaurines, which are the really big-headed ones. That includes a few ancestral things like Albertosaurus and Gorgosaurus, both from Alberta, then Daspletosaurus, a thing I named called Jiuchengtyrannos in China, and then Tarbosaurus and Tyrannosaurus.

You've really only got 3 or 4 of these ultra-giants, which are all kind of 10 meters plus in size and have the really broad skull with a real excessive bite force. But even things like Albertosaurus, which is a big animal—7 or 8 meters and a ton or so—they're not quite T. rex, but they're definitely more robust than the other contemporaneous carnivores.

There is this progression of getting bigger, getting a bigger head, the teeth getting bigger but fewer in number, building up the bone-biting and the power. But there are some interesting evolutionary offshoots, in the way that cats are largely much of a muchness, but then you get things like bobcats and lynx, which are actually quite bulky, stocky little cats that don't have the long tail and are doing something quite different.

Lex Fridman

Can you just speak more generally? T. rex is one of the great apex predators in the history of Earth. How does an apex predator evolve? Why did T. rex win? Why isn't there a vicious race to the top where everyone's—

David Hone

I have a problem with the term “apex predator” because, ecologically, apex predators are generally defined as things that eat other predators. A great white shark is one because it's eating things like tuna and sea lions, which are themselves predators, so it's a predator of predators. Whereas people love saying lions are apex predators, and they love saying T. rex is an apex predator. They're eating herbivores.

This is not some weird and unusual thing. They're the largest predator in their ecosystem, and they are a giant one. My friend Darren Naish has moved to using the word “arch predator,” so it's some kind of massive thing, but avoiding the term “apex” because I think that leads into a—

Lex Fridman

An important one. I just learned something new today. I didn't understand. I thought I was using the word “apex predator” to mean that.

David Hone

But that's because everyone keeps using it when I don't think they should. Now you're getting into linguistics: if everyone uses it to mean that, does it now mean that rather than what it should mean? I'm probably losing that argument, because you'll probably find way more stuff calling it an apex predator than you will an arch predator, but here we are.

Lex Fridman

Arch predator. Beautiful. I learned something today.

But you're saying T. rex didn't eat other predators?

David Hone

Well, it's probably not going to. We can get into—though I'd prefer not to, because it's tedious—the argument of whether or not there are these small things which some people have said are a different group called Nanotyrannus, or a different species called Nanotyrannus.

Fundamentally, T. rex is definitely weird, even compared to all the other giant tyrannosaurs that are very closely related to it, because it is by far, ludicrously by far, the largest carnivore in its ecosystem.

Lex Fridman

So it doesn't really have competition?

David Hone

I mean, this is a Velociraptor skull. There are some carnivores that are a bit bigger than this, but not enormously so, that were knocking around with T. rex.

Lex Fridman

Right, but think about that. That's like going to Africa and going, “Okay, there are lions. What's the next biggest predator?” And it's like, well, there's a weasel about this big. It's that kind of size difference, and you don't get that normally in ecosystems.

So it didn't have some of the other big dinosaurs around it?

David Hone

Not carnivores. There are huge herbivores.

Lex Fridman

Oh, I see. It would eat those juvenile herbivores.

David Hone

Oh, yeah. It's going to be eating Triceratops and Edmontosaurus and Parasaurolophus. There's even a couple of giant sauropods knocking around in some places.

Lex Fridman

Got it.

David Hone

It's going to be hoovering them up, but how often is it going to eat something the size of an adult Velociraptor? Again, Velociraptor isn't there, but they're a fraction of our size, and we're probably too small. This is like lions hunting mice. You're just not going to—unless one virtually runs into your mouth—go and try to eat it.

Lex Fridman

So the question still stands about arch predators: How do you win in evolution?

David Hone

There's no real winners; there's just turnover, because ultimately, the birds—it still lost out when things went wrong. As we were just talking about, things do tend to lose out when they're big. They're just so much more vulnerable to extinction.

Clearly, dinosaurian ecosystems had much bigger herbivores and, therefore, by extension, much bigger carnivores than any system we've seen before or after. Even in relatively sparse ones, like bits of the Late Triassic, when the dinosaurs were really just getting going, or the very Early Jurassic, you've still got some multiton herbivores and then some multiple-100-kilogram predators, so about as big as elephants and lions get today.

Once you're in the Jurassic and Cretaceous, it is entirely normal to have multiple species that are 10, 20, 30 tons plus as herbivores and anything up to 5 tons as a carnivore. T. rex is probably the biggest of them, but fully terrestrial carnivores that exceed a ton—there are dozens of species of dinosaurs.

Lex Fridman

Is it interesting to you that no other carnivorous predator was able to develop in that environment over millions of years?

David Hone

They're probably just ecologically dominant in the way that mammals are now. Crocs get bigger than lions and tigers, but they're fundamentally tied to the water. You don't see crocs roaming the Serengeti or anything like that.

The really big crocs even now get to over a ton, so those are very serious animals. I think big polar bears are in the 500-kilogram range, though, again, they hunt a lot of stuff in water. Things like grizzlies are at least partially herbivorous or omnivorous.

Lex Fridman

There was a very large marine reptile, Mosasaurus. Did T. rex ever come across that?

David Hone

In theory, at least, the really giant mosasaurs are much bigger, in the same way that, unsurprisingly, whales are much bigger than terrestrial carnivores now. Jurassic Park, unsurprisingly, has rather exaggerated it, so the one from, I think, Jurassic World is like twice the size it should be.

Some of these things were still 15 or 20 meters. Some of them were absolutely giant. We had one dug up in the UK just a couple of years ago, and I got to see the skull of it—or a cast of the skull—and it's about the same size as a T. rex skull.

Lex Fridman

If we take a ridiculous detour before we get back to science, what creature in the history of Earth would challenge a T. rex in a fight, would you say?

David Hone

On land?

Lex Fridman

On land.

David Hone

Nothing reasonable. The only other thing you can really add is—this might be a very British adage—“It's not the size of the dog in the fight; it's the size of the fight in the dog.”

Maybe there's something a bit smaller which is just hyper-aggressive, and that would be enough to win, like the classic honey badgers chasing off lions. It's not that a honey badger would win in a fight, but if the honey badger is prepared to put up that much of a fight and the lion really doesn't want to get hurt, then it kind of technically wins.

Lex Fridman

You can't imagine any of the cats—tigers, none of them can do it? I mean, the size difference, the power of the jaw, all of that kind of stuff.

David Hone

Going to T. rex, what could reasonably challenge it? There's a couple of other giant tyrannosaurs, and there's a couple of giant carcharodontosaurs from South America that I would say are comparable in linear measurements, but are probably rather smaller and rather lighter. In which case, your money is going to be on the bigger guy with the bigger bite. That simply is T. rex.

Lex Fridman

The bite is important.

David Hone

Yeah, I think it is. These guys, the carcharodontosaurs, are much more cutting. They're really killing stuff probably by grappling with the arms, because they do have big, muscular arms with big claws, and then slashing away at stuff.

I think they're probably doing something more like wolves or hyenas, or almost like a hunting dog, where they're harrying stuff and slashing at it, basically bleeding them out and wearing them down.

Lex Fridman

What about that strategy? Maybe you could speak to biting strategy. T. rex is a relatively slow bite but extremely powerful. What about animals that have very fast bites?

David Hone

It's very simple mechanics. If you have a very long jaw, you're going to close faster but with less power at the tip than if you have a really short one that's deep. That's really it.

Let's say there are things like the Alioramini, and then there are things like Velociraptor and a lot of its relatives—really very small but narrow. They are narrow-snouted. There's not going to be a lot of fundamental strength here. The teeth are very numerous and very small, so they're much more about grabbing something tiny. Velociraptors eating rat-sized stuff—that's probably going to be its primary diet or kind of diet.

Lex Fridman

I wonder if there are a bunch of smaller, fast-biting things that could just bleed a T. rex to death.

David Hone

They're going to struggle, though. I remember doing some work for one documentary where they literally wanted Velociraptor fighting a T. rex, and I was sort of like, “You do know this is, like—we're going to shoot some meerkats killing a lion.” You can film it, but no one would believe it because these ankle-high things trying to savage a shin bone are—yeah, I'm sure they'll make some holes and it'll lose some blood, and it may not be very happy, but I don't think they're going to win.

Lex Fridman

The size of a Velociraptor was exaggerated by Jurassic Park.

David Hone

Oh, enormously. I mean, they get a bit bigger than this in terms of the skull. But, yeah, they're kind of thigh-high to me, like a meter or so to the top of the head, 2 meters long, whereas in the movies, they're standing taller than guys who are 6 feet. So it's just massively, massively scaled up, and then these big, domey heads, rather than the really long, narrow snout.

Lex Fridman

Maybe we could take that and change it. What does the Jurassic Park and Jurassic World franchise get right and wrong?

David Hone

I mean, they get a hell of a lot wrong.

Lex Fridman

What are some of the really definitive things that are interesting to you that it gets wrong, and also what are the things it gets pretty close to right?

David Hone

I just want to preface my answer because I always get asked about this, understandably. I get that it's a movie. But if someone's going to ask me, “What does it get wrong?” I'm going to give them an answer. But I do get people going, “Ah, you're just nitpicking. Ah, you know it's fiction. Ah, you know it's made up.” Yeah, I do know. But someone asked the question, so here's the answer.

Lex Fridman

I should say that some of the things that I've heard you describe, I feel like it's the responsibility of those folks to get it right. I think there's something I really deeply admire. There's a show called Chernobyl. They don't need to be that accurate, but they really care about the detail of the kitchenware in a room, just to get the tiniest detail right. Who's that for? I don't know who that's for, but that's for great art. That's for the spirit of the thing. And if you focus on getting those tiny details right, some magical thing happens with the bigger story. If you don't care about the details, the story gets corrupted.

So I just wanted to say that some of the things you describe, like how many fingers—it's important to get that right, because if you do, some magical stuff can really emerge. It could become a legendary film as opposed to just a summer hit. That's my take.

David Hone

Again, I've worked on documentaries where they're claiming that accuracy is absolutely critical and 100% important, and they won't put anything on screen that I haven't told them to. Then many of those things turn out not to be quite as true as advertised once you get around to it. So I'm aware that even documentaries will take massive liberties. You can't be too harsh on popular fiction.

On the other hand, I am also aware that it is, by far, by a ludicrous degree, the most popular bit of any kind of media that includes my work, as it were, or something that I'm actively engaged in and know about. And so, whether or not it should have that influence or the filmmakers should have responsibility, it does. It does have that knock-on effect.

It's as simple as the idea that a T. rex can't see if you don't move. Yeah, it could. I don't know where that came from. As far as I can tell, Crichton just dreamed it up. In The Lost World, his sequel book, he hints that there's a research paper that says it, and that's where he got it from. There's a second paleontologist character who's advising Dodgson, the evil BioSyn guy, and he says, “Oh, no, well, that's from such-and-such's research.”

I tried looking it up. As far as I can tell, it doesn't exist and never did. So I think it's just straight fiction. It works for the book and it works for the movie, but as far as I can tell, it's straight fiction and Crichton just made it up. If it's buried in some bit of literature, he's done better finding it than I have, and I've had a really good look and I know how to look. I've never come across anyone who's found it, either.

But it just warps the perception. Velociraptor: cheetah speed, pack hunters, super-intelligent, giant-sized animals. And, okay, 1993, it's a bit more forgivable, but even then, we were pretty confident they had feathers.

Lex Fridman

Is any of that true? Wait, so—

David Hone

Probably not.

Lex Fridman

The pack-hunter aspect of it?

David Hone

That's something I've written quite a lot about. The evidence for pack hunting in any dinosaur at all is almost nonexistent. It basically doesn't exist. And that's going exactly back to that stuff we were talking about: bite marks and taphonomy, the history of specimens, and how you interpret stuff.

Lex Fridman

What kind of evidence would show, like, maybe bite marks from multiple sources?

David Hone

It's really, really tough. The main one which was put forward is this famous association in Montana of Deinonychus, which is often confused with Velociraptor, including in the books and movie. Basically, a bigger version of this that's rather older, from the Early Cretaceous, and a thing called Tenontosaurus, which is kind of iguanodontian—an Iguanodon with spiky thumbs. Basically, otherwise, a fairly run-of-the-mill herbivore.

There are 2 sites, I believe, for this, but there's 1 that's much more important, where you have a Tenontosaurus carcass with Deinonychus carcasses. The interpretation of this is, well, this is a group that brought down the herbivore. Of course, the immediate counterargument to that is, “Well, why did they all die there?” When lions kill a wildebeest, they eat it. They don't all just die next to it.

Or even if they did kill it and start eating it, and then got into a fight and killed each other, lions as a species are not going to hang around for very long if every time they kill something they get into a mortal fight and kill half their pride. There's nothing obvious that killed them, but it's at least possible that this was something like a predator trap.

Predator traps are really neat. La Brea Tar Pits is a classic example. The idea is a herbivore stumbles into something like tar. You've got your deer or wildebeest or mammoth or whatever it is, waist-deep in tar and going, “I'm dying, I'm dying,” and making horrible noises. Smilodon walks over and goes, “Great,” and wades out after it, and he's now stuck.

Then the next one, and then the next one, and the next one, and the next one. And then, lo and behold, you now have something like La Brea, where they've got—the numbers are something absurd. I think they've got 3 mammoths and 1 ground sloth, and then 100 dire wolves and 40 Smilodon, because it's just sucking the carnivores in.

Lex Fridman

Wow.

David Hone

You get these really distorted ratios. I don't think that's the case with the Deinonychus-Tenontosaurus stuff, because there are ways that you can probably rule that out. But there are probably places like this where it's happened. Again, the other one is the toxin one, whose name—

Lex Fridman

Yeah, Cleveland-Lloyd, so it's just coming up on your screen.

David Hone

That's another one with loads of dinosaurs. There's Allosaurus. But we've definitely seen it with—I think this has come up with something like lions or wolves. They found loads of them dead by a lake, or this pond, and it turned out this pond had some really nasty algal-bloom toxin in it.

The interpretation was the same kind of thing: a couple of deer were drinking, this stuff's toxic and kills you within minutes. It keels over and dies. A wolf smells dead meat, comes over, starts eating it, has a drink, keels over and dies. So you're not getting physically sucked in and trapped; you're just dying from the toxicity. But the same effect can happen, and you just end up with a pile of dead bodies.

Lex Fridman

Fossil discoveries, including parallel trackways and bone beds containing multiple tyrannosaurs, suggest that these large predators sometimes moved and possibly hunted in groups. You, as a person who wrote a book about the behavior of dinosaurs—

David Hone

Yep. Let me deconstruct that almost instantly. It's really easy, because this is exactly the kind of thing I'm talking about in my book on dinosaur behavior. The tyrannosaur trackways of a group of tyrannosaurs are, I think, 4 or 5 tracks total. So it's 2 from 1 animal, 2 from a second animal, and 1 from a third animal.

That's not the end of the world. That's somehow how trackways form. The rock's broken up. They stood on mud, and then they didn't. Whatever.

Lex Fridman

Just to clarify, trackways means footprints from multiple steps?

David Hone

Yeah. One of them has got a left and right, and the other 2 don't.

It's very fragmentary, but that's not a problem with the interpretation. The problem is that this is interpreted as a group of them moving together. Why? Because they're going in roughly the same direction, and they're roughly equal sizes.

I've seen solitary animals moving in groups. A guy I know quite well in South Africa—I go to South Africa regularly for my teaching, actually—is one of the big guys at South African National Parks, and he gives me the skinny on all kinds of weird stuff. He was telling me a few years ago that one of his park rangers had observed leopards hunting together in a group.

Now, leopards are basically not just solitary; they're antisocial. They beat the hell out of each other if they come near each other. But I've also seen game trails. Game trails are paths that single animals take. If a female is in heat, males will track her down and follow her.

You'll get one set of footprints, and then a couple of hours later a male will come past, and a couple of hours later another male will come past. Now you've got 3 sets of footprints all traveling in the same direction on the same bit of path, but they live on their own. That's without even considering hunting together, which is a massive step above this.

The one I've talked about quite a bit in my book is the spotted hyena, Crocuta crocuta, which is the one everyone knows. There's a whole bunch of hyenas, but this is the big laughing hyena. You can see plenty of Attenborough-type documentaries of them—7 or 8 of them, or even 10 or 12 of them—going into a herd and ripping apart wildebeest or zebra or whatever it is.

But actually, if you read the scientific literature, this is really rare. They mostly hunt on their own. Now, they do live in these social clans with hierarchies and complex social interactions. They are very social animals, but they mostly hunt on their own.

Even if you find loads of trackways of them moving together, again, there's 1, if not 2, examples for tyrannosaurs where we've got multiple tyrannosaurs together, and that's been argued for pack hunting. At best, that argues they might have lived together, but it doesn't tell you whether or not they hunted together.

Lex Fridman

So how can we make a decision one way or the other?

David Hone

I tend to be ultra-conservative in this context, and I think we should probably avoid saying things that we're not quite confident about. I don't want to ever go down the, "We must have really definitive, 100% convincing evidence" route, because this is paleo, and we don't have that kind of data.

But just as I talked about with things like the predator-prey size ratio stuff, there is data we can start to use on living species about what tends to trigger hunting in groups or living in groups, and what data there might be from things like brain sizes or other trackways. We do have bite marks indicating prey size. If you start finding repeated attacks on big prey from relatively small predators, that would be quite convincing. As you said, maybe we had bite marks of multiple different sizes.

Now, that on its own is difficult, because, obviously, with scavenging, tyrannosaurs are an exception. Most carnivorous dinosaurs have pretty similarly shaped teeth, so how easy is it to tell an adult from a juvenile, or an adult from a different species that's just a bit smaller? Probably pretty tricky.

For me, I think the kind of gold standard—which I don't think we're ever going to find, but you never know—is that you could, in theory, get a trackway of something like a herbivore with a whole bunch of carnivore tracks coming by it. We do have a couple like this, but they don't have what I really want to see.

If you trace the footprints of the individual carnivores, and A's footprints go on top of B's early on, but later on B's go on top of A's, they must have been there at the same time, because there's no way they could have been even minutes or hours apart. If you had that, then those 2 must have been together, or at least within sight of each other, and one wasn't turning around and roaring or having a fight.

If you can do that with 7 or 8, all converging on 1 herbivore, and then everything goes manic, that's really pretty convincing.

Lex Fridman

It is so fascinating and awesome, the Sherlock Holmes aspect of paleontology—figuring things out when you have very little signal and you have to figure out the puzzle from that. You're brilliant. You're giving so many brilliant examples of how, if A steps on top of B, and then B steps on top of A, that's a strong signal that they were walking together.

Steve Brusatte

I am a bit of a Sherlock Holmes fan, and he references Cuvier. Baron Cuvier was this legendary French anatomist. He was the first guy to posit that things went extinct, working on mammoths. He said, "Well, there's nothing like this alive today, so extinction happens," which, before that, we didn't really know.

Holmes has a line about, "Just as Cuvier can restore an animal from the smallest bone, so I can restore the events from the smallest detail."

Lex Fridman

Damn.

Steve Brusatte

I'm paraphrasing, but I'm not far off.

Lex Fridman

Yeah, there's truth to that. You have used an analogy that Conan Doyle specifically used for Holmes, going back to paleontology.

Steve Brusatte

I mean, it's obvious. It's clear. It's right there.

Lex Fridman

That's how on the nose you are with that one.

So, basically, you clarified and showed all the things Jurassic Park got wrong.

Steve Brusatte

Yeah, we got off-topic before we even got onto Jurassic Park.

Lex Fridman

And just Velociraptor—you said the size, the pack hunting, all of that.

Steve Brusatte

The pack hunting, just to round off on that, I don't know. Maybe there's actually been some more recent stuff on Deinonychus, looking at things like isotopes in the teeth, feeding traces, and some other stuff that's hinting that maybe there is more going on there, which is great. I'm not anti the idea that this exists, but you absolutely get this buildup of the idea that Velociraptors are pack hunters from Deinonychus, and I think the evidence from Deinonychus is really weak.

Okay, lions are group hunters. We know they are. Does that mean that leopards are, and tigers and pumas? No. So why on earth do you think that just because Velociraptor—group hunting has all kinds of more complicated dynamics going on than just close relatives tending to do it?

You can flip that around. African hunting dogs, wolves, things like bush dogs—there are various canids that all hunt in groups, but then you've got things like maned wolves, which are effectively solitary. The hyenas—spotted hyenas are these super-social animals, but the brown hyena, the striped hyena, and the aardwolf are solitary. You just can't do group versus solitary based on close relatives or anything like that.

I am very sure a ton of dinosaurs were aggregating, living in groups to some degree. I'm very sure some of them were social, with complex lives and hierarchies, and even pack hunting. Which ones? I have very little idea, because I think the data is so sparse that we can't really say it with any confidence for anything, in my opinion.

I think that can be gotten at. I think we need to start getting at it with the sort of stuff I'm talking about: getting a better understanding of what drives sociality in lions versus tigers versus leopards—relatively close relatives that overlap. Don't forget, in India, leopards and tigers overlap with lions. The Asiatic lion is still there.

You can talk about ecosystem structure, prey size, prey type, and all this stuff. Maybe we can start piecing that together a bit better and then apply that to things like the trackways, the isotopes, and all the rest of it—bite marks and these mass-mortality sites.

I think it can be done, but personally, what were pack hunters? No idea. I don't think any of them were, in the sense that I don't think we've got good evidence for any of them. But there probably exists on Earth definitive evidence one way or the other.

Lex Fridman

But there probably exists on Earth definitive evidence one way or the other.

Steve Brusatte

Yeah, probably for some of them. I think it's well within their scope. One of the papers writing about this, ironically arguing against pack hunting in Deinonychus, said, "Well, it's probably not the case because you don't really see pack hunting in birds. And so if you don't see it in birds, then dinosaurs being their ancestors—well, if birds can't evolve it, then maybe dinosaurs couldn't have evolved it."

I'm not sure that's a great logical argument, because of the complexities of social behavior anyway.

But then there are a couple of birds which actively hunt in groups. Things like the ground hornbills in Ethiopia and South Africa are a really good example of that. So that point is incorrect.

Then, if not true sociality, we see cooperation in crocodilians, and we're seeing degrees of social behavior in things like iguanas. The idea that, “Well, birds are super advanced and dinosaurs can't do it because the stupid reptiles are too stupid, and therefore dinosaurs are more like them,” which isn't quite what they're saying, but it's sort of the unwritten idea. “Well, we have social behavior and cooperation behavior in crocs and in lizards.”

So that really gives you the impression that dinosaurs, theoretically at least, are perfectly capable of that. So there's pack hunting, but there's also sociality, which is such an interesting idea. How did they live? This is something paleontology doesn't often touch—the lives of these animals.

Lex Fridman

Yeah, because animals are doing complicated things. So, in the case of lions, a large part of this is down to territoriality, in that the males ultimately are defending the territory, and that's effectively protecting the females. But, of course, what they're mostly protecting them from is other males.

So there's a ludicrous bit of self-interest. But that's effectively how it's operating as a system.

Steve Brusatte

But it could just be predatory-type behavior. Cheetahs are my go-to example for this. Cheetahs are the weird ones compared to the other cats because females are solitary, but males are social.

So, when the female has 5 or 6 cubs, the brothers will stay together in a group, and then the girls will go off on their own. If you're the only brother or the only survivor, you will usually hook up with a gang of other males. So cheetahs are pack hunters if you're male and solitary hunters if you're female.

So it's not about territory defense or occupation for them. It's about prey type.

Lex Fridman

Is it possible to know the sex of a T. rex or any of the other dinosaurs? What can paleontology show us?

Steve Brusatte

In theory, yes. In practice, it's way more complicated. Unless you get very lucky, we have a handful of specimens that still have eggs inside them—an instant giveaway. But this is 2 or 3 specimens.

What you can look for is that both reptiles and birds have a thing called medullary bone. When you're laying eggs, you need a lot of calcium very quickly because the eggshell goes on basically at the last minute during egg development. So you need a lot of calcium very quickly.

During the laying season, these animals grow this really weird kind of bone texture on big bones like the femur and the humerus—really big bones in the body. It has a weird texture because it's full of blood vessels, and it's full of blood vessels so that you can basically apply a lot of blood supply to it quickly, suck up some of the calcium from that bone, take it through the system, put it on the eggs, and lay your eggs.

We can find that. If you have a dinosaur bone and it's the right kind of thing—you can't do it on a finger or a claw or a bit of rib, but on a nice big bone—you could cut a chunk of that out, grind it down to the point that it's virtually transparent, a fraction of a millimeter thick, put it under a microscope, and have a look.

If you see the right bone texture, there are some exceptions, but that's very probably medullary bone, and you have yourself a female. So the instant assumption is, “Okay, so you can tell female from male.” No, we can tell a laying female from everything else.

Males won't have medullary bone. Young females won't have it. Females outside of the breeding season won't have it. Females inside the breeding season that have been really sick that year don't have it. Or, if they laid their eggs early and now they don't need it anymore, they won't have it.

Occasionally, if you cut up a bone—which, of course, we try not to do that much—you can get the signal of medullary bone and infer that you have a female in the breeding season.

Lex Fridman

But so there's no large bone-structure differences?

Steve Brusatte

Well, maybe there are, but we haven't seen them. You look at things like kudu or blackbuck and all kinds of antelope, or even most deer, and the males have horns or antlers and the females don't.

Then you look at something like Triceratops and all the ceratopsians. There's a big clade of—oh, it must be 40 species by now—and every single one of them has the frill and has some kind of horn somewhere. You don't have the hornless ones or the frill-less ones in the way that we do with a lot of these animals.

Lex Fridman

I'm trying to figure out: in how many of the species is it obvious that there are pelvis differences, all that kind of stuff?

Steve Brusatte

Pelvis differences work on humans and apes and maybe a couple of other mammals, but it's mostly not very good. That's because we give birth to such a gigantic baby with a gigantic head compared to our size that women have different pelvises from men.

Lex Fridman

And then there are size differences. The skull is not as reliable as the pelvis.

Steve Brusatte

It's not. And then again, you just need to look at humans. Humans are always slightly dodgy with this because of our evolutionary and cultural history. There are population differences. There are maned female lions in places, and there are maneless male lions in places.

Reindeer females have antlers in winter. So Rudolph was a girl, because every illustration of Santa and his reindeer ever shows them with antlers, and that's a female reindeer, not a male, if it's winter.

Lex Fridman

So basically, we don't know much about the dating and the sex lives of T. rexes.

Darren Naish

Well, not much, but you can make some inferences. For example, all tyrannosaurs have at least some kind of crest on the head. The early ones have this midline crest. It really doesn't work on a human. They have a midline crest running along the top of the nose that sticks up.

The later ones largely don't, but they do have this weird armored structure along those fused nasals, and then they have little horns over the eyes. Those, as far as we can tell, don't really have any kind of obvious mechanical function. Outside of the feathered dinosaurs, the vast majority of carnivorous dinosaurs have some kind of crestal display feature on the head.

Lex Fridman

When you say “display feature,” meaning for sex appeal, to attract mates?

Darren Naish

Or something like that. I've always favored the term “socio-sexual selection” to cover both sexual display and sexual dominance and communication, but also social ones, because those 2 things are hard to tell apart.

Female lions find males with darker manes sexier, but male lions find males with darker manes more intimidating. So one of them is sex, but one of them is social.

Lex Fridman

Nice. I guess it goes hand in hand, sure. Yeah.

Darren Naish

It can, but then you get things like the other example I go for: black swans, these beautiful Australian birds. They have these really weird, curly feathers on their wings.

Males and females both have them. Males prefer females with curlier feathers, and females prefer males with curlier feathers. There's an obvious sexual link, but then females fight too. Females fight over the best nesting spots, and the females with the curliest feathers tend to win those fights.

Lex Fridman

How does that make sense?

Darren Naish

This gets into classic sexual selection theory. It's what's called an honest signal. You couldn't have those curly feathers if you weren't able to support them, because they're the primary feathers on the wings, and what they actually do is make it harder to fly.

So you're basically going, “Look how tough I am. I've grown this big, and I can fly and carry on with my giant, curly feathers because I'm really tough and I'm in good shape.”

It's the same with the lion. The reason you get pale lions in the south is because it's close to the equator, because it's too hot. So there's the trade-off: if you have a really black mane, all the males know you're a badass and all the females know you're super sexy, but you just die of overheating.

The trade-off is, if the heat's going to kill you, you're probably better off being a bit paler and surviving in order to reproduce than you are being jet black but just dying instantly as soon as it gets hot.

Lex Fridman

So there are trade-offs there, okay.

Darren Naish

Yeah, and that's probably what's happening with the theropods. All the little crests and horns—Ceratosaurus, Dilophosaurus, tyrannosaurs, allosaurs have big crests over the eyes, and all kinds of others.

I've written about this. I think this is the trade-off. You're going for the sexiest look, and the sexiest look is the biggest horns or the biggest spikes and whatever's on the head, probably also with the brightest colors and the most display patterns. But this also gives you away to your prey.

If you're trying to hide or you're trying to sneak up on something, being brightly colored or having stripes or all this extra stuff on your head means you get spotted.

But then that's the trade-off: if I'm this big, and my horns are this big and this red and yellow, and I can still—whoop—I can still run those guys down and hunt them and kill them and eat them, then look how great I must be. Whereas that little guy, he's only got weedy little crests, and they're really dark because he's so bad at catching stuff. He doesn't have the extra energy to grow big crests.

And that's why, when you're a herbivore, you don't have that pressure, particularly something like—this is Protoceratops—but somebody like Triceratops and these guys, they're living in big groups. You can't hide from a predator when you're a group of 20 animals that are 10 tons each, so who cares? You just grow the biggest signal you can possibly grow, and lo and behold, they have giant frills and giant horns.

Lex Fridman

What can you say about beauty in evolution? Something that's—maybe you can educate me—but something that's not quite an honest signal, that's just pure beauty, like peacock feathers?

Darren Naish

So there are things which we think operate closer to that. These are the 2 classic ideas of sexual selection, and both are probably true to certain degrees in various different species. One is the honest signal, or the—it's the kind of handicap hypothesis, because you're holding yourself back whilst proving you can still do it. I ran the marathon carrying a couple of weights. You're obviously stronger than the guy who ran the marathon without.

And so that's why it's an honest signal, and it's why it's a handicap. But the other one is what's called the sexy sons hypothesis. The idea is a female might just find a male attractive for no other reason than random. There is some component of her brain, or whatever it may be, that just looks cool, and you can actually sort of get this as a human. Forget human beauty: you can look at a bottle and go, “That bottle's kind of nice, and that bottle's kind of ugly.”

Lex Fridman

Where do you put birds? Birds are interesting with this. Where do you put peacock feathers?

Darren Naish

So they're probably more of a handicap hypothesis because of the colors that go into them and the sheer size and shape.

Lex Fridman

Oh, I see. Yeah, yeah, yeah.

Darren Naish

These things basically can't fly. They're really vulnerable to predators.

Lex Fridman

Can the handicap hypothesis explain just how beautiful peacock feathers get?

Darren Naish

So, probably not entirely. There's almost certainly randomness going on in there as well. And the eye spots—we know that eye spots are attractive—are probably encoded in some way. But yeah, going back to the sexy sons, the idea is females prefer something different for whatever reason, and there might actually be some reasons females prefer things that are different. Different usually means separate and outside, and that usually comes with variation inherently.

Lex Fridman

Oh, so variation is an evolutionary turn-on?

Darren Naish

Yeah, basically.

Lex Fridman

Wouldn't it? Man, you're rolling the dice, though, aren't you?

Darren Naish

You've got to remember, again, it's really easy to look at that sort of thing with a human perspective where, at maximum reproductive output, I think the record—there's some obscure record—is something like 66 children, which is probably apocryphal, for a Russian woman who had loads of triplets and quads. But humans don't have many offspring, whereas most animals lay dozens of eggs or hundreds of eggs or thousands of eggs at a time.

Lex Fridman

So diversity pays off more there?

Darren Naish

So diversity can pay off. We think that's probably a major part of the reason that sex evolved in the first place: it gives you resistance to a changing environment, and it gives you resistance to parasites and diseases, which often reproduce way faster than you do. Bacteria can divide in a few hours. We reproduce every 20 years. That's quite a difference.

If we were all asexual clones and you're vulnerable to some disease, you're probably going to get wiped out. Look at the Irish Potato Famine, or something like that. So different may be appealing simply because it is different—variation. And there's at least some evidence for that.

There are swordtails. If anyone's a tropical fish keeper, swordtails are really quite common little tropical fish that you can get in all kinds of aquarium shops, and they're a very boring fish shape. Their tail has a big spike on it, and that's the name. They're really close relatives of a group called the mollies, which basically don't have that.

In the wild, these are Mesoamerican fish; they don't usually encounter each other. But even if you go and get—not even the domesticated form, because these things have been bred for decades at this point—you can go and get some wild mollies and give them a wild male swordtail, and they think he's so much better than all the male mollies. They will go for that one, and they will preferentially mate with that one.

We don't know the exact mechanism, but it appears to be: he looks similar enough that I recognize it as a potential mate, but different enough that this is exciting. And then this is where the sexy sons kick in, because the females are now assuming those animals are successful, and they can hybridize, or maybe it's just a male who happens to be a little bit blue or a little bit red or whatever it may be.

Well, the female offspring, the daughters, are probably going to inherit their mother's preference: “I really like red.” And the males are probably going to have red in them because their dad had more red. So guess what the next generation does? There's more red, and the females like more red, and you don't have to come back much further, and suddenly all the males are bright red. And that's closer to beauty than I think almost anything else would be, with still a naturalistic explanation.

Lex Fridman

We kind of started talking about beauty from how much social life a T. rex might have, so just to take that to a place of what we know and what we don't know: can we know something about their social life, where they lived, how they lived?

Darren Naish

The very fact that they have these apparently socio-sexually selected signals—the little crests and stuff on the head—points to a branch of sexual selection called mutual sexual selection, and the black swans are an example of this. The classic sexual selection is your peacocks and your lions and things like this. Males are bigger and more flamboyant and whatever it is, and they're doing all the competing.

But mutual sexual selection—and this is really common in a whole bunch of things that people are familiar with but don't know—occurs in loads of seabirds, starlings, the common starling that we have in Europe and that has been introduced into the U.S., parrots, and various other things. Basically, males and females invest similarly in rearing the offspring.

The idea generally, both with handicap and sexy sons, but particularly with handicap, is the idea that males are proving their worth. They're basically saying, “I'm the biggest, strongest, healthiest, I've got the best genes, I should be the father of your offspring.” They go around showing off and then mate with as many females as possible.

The females then do all the work and make the nest and look after the chicks and rear them or give birth or whatever it may be. Yada, yada, yada.

So the idea with mutual sexual selection is, what if there's not much food around? Things like puffins or penguins in the Arctic, where the male sits with the egg and the female toddles off, gets food, and then comes back 2 months later or whatever it is. On their own, they can't rear the offspring. They have to have male investment.

Well, suddenly the male's now putting loads of effort in, so the male's now in the same position that a female would be in under normal conditions. You don't want to be the sexiest, toughest, biggest male, and you can only mate once, all right? There are various cheats, but we won't get into that just yet.

You're only going to mate once, and you're going to put all your effort into helping rear offspring, rather than chasing down as many girls as possible. Are you going to go for the biggest, fittest female as well, or are you going to go for the small, weedy one that doesn't look very well? You go for the best one.

Well, how do you know that? Well, because she's got a crest as well, and so suddenly you now get mutual ornamentation, just like the black swans, where the males are checking out the curliest females and the females are checking out the curliest males, and you'll see they mutually pair up.

This is what we see with things like starlings. Males like the brightest females, females like the brightest males; they tend to form pairs. The darkest and least bright ones are obviously kind of left with each other at the bottom of the pile. They tend to pair up.

But it means that when you've got signals in both males and females, like every Triceratops or every Tyrannosaurus, it at least hints that they're going down this route and that they might cooperate for reproduction.

Lex Fridman

Wow. Another weak signal that tells a powerful story.

Steve Brusatte

Yeah, and the problem is it's compromised by lots of things. So that goes back to your earlier question about telling males from females apart. The vast majority of dinosaur species, like 90-plus percent, are known from a single specimen, and a specimen is not necessarily very complete at all. It might be a couple of bones, it might be 1 bone, it might be a tooth in a couple of cases.

The actual number where we've got a decent number of real whole skeletons that we can actually compare to each other is less than 10—probably more like 5 or 6.

Lex Fridman

Can I ask you a weird question? Let's say all humans died right now: press a button, poof, gone. How much of human civilization would you be able to reconstruct from just the skeletons that are in the ground? You just start collecting skeletons.

Steve Brusatte

There's a lot of them. There are billions of them.

Lex Fridman

Would you be able to start telling a story, like urban centers?

Steve Brusatte

Yeah, probably, because—

Lex Fridman

You could probably reconstruct a lot, right?

Steve Brusatte

And if nothing else, just the superlative brain cavity will tell you quite a lot.

Lex Fridman

Yeah, the intelligence.

Steve Brusatte

Must have been very, very smart with—

Lex Fridman

You could—

Steve Brusatte

—a brain that big.

Lex Fridman

You can probably reconstruct some of the behavior—a lot of the behavior, social behavior. A lot of this stuff.

And you're going to see stuff like the famous one of—I think it was a Neanderthal. There was a famous question: “At what point do you think society exists?” Maybe it was one of the Leakeys, but the answer was basically this skeleton, because it was someone with a real, properly busted leg that then fully healed. If that person was on their own, they would have died. Someone had to look after them for months to get that level of healing. You only do that to someone you're really devoted to, and probably a group of people, because even one person can't look after one other person, right? So that's your society.

And yet you think about the pathology of skeletons in the human race. How many of us have broken a bone? Most adults have probably broken a couple of bones, even if it's just a finger or a nose or something. But then you think about what medicine has done, and you would be able to see treatments of complete compound fractures of guys who survived horrific car crashes, and treatments of cancer, bone cancers, and stuff like that. You would see that. How is that happening? Either they're magic, or they've got some kind of—

Steve Brusatte

That just hints at the fact that the evidence collection and the reasoning mechanisms that paleontology and archaeology use are really powerful.

Lex Fridman

Yeah, it is. And so it could be very effective even just with a small amount of data. I mean, you could—

Steve Brusatte

But it's the right amount of data. That's the thing. We can find dozens of skeletons that we can't do very much with, and then the right one—things like stomach contents, or bite marks, are super powerful bits of data, but they don't turn up that often. It's not like you can get them off every skeleton. That's the thing: it's the pool of data, and I think that's what people miss.

We, as paleontologists, get caught up on single superlative specimens and then try to treat them as a silver bullet almost. So Microraptor, which I mentioned before, is a little flying dinosaur—a crow-sized, or gliding, dinosaur—from China. We've got at least a dozen good specimens of it by now, and multiple ones with stomach contents. There's one I've described with a little mammal foot inside it, there's one with a bird inside it, there's one with a lizard inside it, and there's one with a fish inside it.

On their own—and this happened for at least 2 of the papers describing these things—it's like, “It ate fish. These are fish-eating animals.” No, that one ate one fish once. That one ate one bird once, that one ate one mammal once, and that one ate one lizard once. So what have we actually got here? I suspect we've got a group of generalists, and we just happen to have found them eating different things at different times.

But equally, it's also possible that this is one of these things, and it had learned to eat fish when the others hadn't. Maybe this was mostly fish eaters, and the others ate whatever they could get. Maybe one caught a bird up a tree in a nest. Maybe one found it dead on the ground. You don't really know. One of these things on its own is fascinating, but potentially misleading.

Lex Fridman

Well, the way you're describing it now, it seems like, yes, it's potentially misleading, but in your whole way of being and the way you've been talking about this stuff, I can see that it's not just the direct evidence you're mentioning. It's a bunch of intuitions you build up. It's like you're stitching together a bunch of little things. It's the Sherlock Holmes thing—not just this one piece of evidence.

It's like, “Okay, what do I know about the general other dinosaurs that are on the Earth? The different animals, how animals usually behave around this period, about the environment?” All of that comes together, and then you're figuring out which is true.

Steve Brusatte

And that's—so one thing I've definitely written about is the independent lines of evidence. Can you get stuff that is, as far as possible, truly independent from the other data, and does it give you the same answer? And then when it does—

Lex Fridman

That's powerful.

Steve Brusatte

—that's incredibly powerful. So Spinosaurus, or the spinosaurs as a whole, is my go-to example for this. They're the guys with the famous big sail on their backs and the weird crocodile-like head, though some of them look rather different from that.

If you look across all the species and specimens that we have, they're incredibly fragmentary and very badly known, but they're all basically associated with—when you look at the gestalt, you see a whole bunch of stuff for these things. They do have a surprisingly crocodile-like head and crocodile-like teeth compared to every other carnivorous dinosaur. When you do the mechanical analysis, you see they function in a very similar way.

And indeed, teeth—here's a spinosaur tooth with a very nearly circular cross section, really distinctive, similar to crocodiles, similar to dolphins, similar to fish-eating fish. So, points to fish. Crocodile-like head, points to fish. Crocs eat other stuff too, but still.

They're usually found in or near aquatic systems. Fossils in general tend to turn up in aquatic systems because you've got to be buried to become a fossil. Water association is common, but even so, that's true. They turn up in places where lots of other dinosaurs don't tend to turn up, including carnivores, which suggests they're eating something else.

If you look at the isotopic signature of the teeth, it often correlates with crocodiles, fish, turtles, and stuff that lives in water, and doesn't correlate well with other land-living dinosaurs that lived at the same time and in the same place. So you put all of that together, and it's really hard to argue against it.

In addition to the tiny detail of Baryonyx, the British one, being found with fish scales inside its chest cavity, you put all of that together, and, yeah, I'm not saying it only ate fish. I'm sure it ate big shrimp and turtles. We know they were predating on terrestrial dinosaurs and pterosaurs because, again, of stomach contents and teeth and stuff. But fundamentally, this is an animal, or a group of animals, doing something different from the other carnivorous dinosaurs, and it's probably linked to water, and it's probably linked to fish as a predominant way of living.

Lex Fridman

We should mention that you're working on a book out in early 2026?

David Hone

In the UK, it will be out in November. In North America, January or February 2026.

Lex Fridman

It's called Spinosaur Tales: The Biology and Ecology of Spinosaurus.

David Hone

Written with Mark Witton, who did that picture.

Lex Fridman

It's a beautiful creature.

David Hone

Which I think is in there. Mark's done a ton of new artwork. He helped write the book, but he's also the artist.

Lex Fridman

I mean, can you describe a little bit more about this creature? There's a bunch of stuff like what you just mentioned. There's some debate about the degree to which it's aquatic.

David Hone

Not very, is my take.

Lex Fridman

So, does it live in the water?

David Hone

Yeah. I think it's basically a big wader. It's a poor analogy, but it's a very weird, giant stork.

Lex Fridman

Oh, got it.

David Hone

Or heron.

Lex Fridman

Was giant.

David Hone

Yeah. So potentially bigger than T. rex—linearly, not in mass. Again, a really quite narrow chest versus that T. rex barrel. But potentially 15 meters long, so bigger than any T. rex we've found, at least in terms of length.

Lex Fridman

Can you describe what it looks like? I mean, there are some iconic features to it, right?

David Hone

Yeah. So, this really quite long head, with a kind of wavy jawline. Most carnivores have straight jaws. This one has a somewhat wiggly jawline. It really narrows at the front and then opens up again into a little—it's called a rosette. So you've got a little semicircle, and then a dip, and then the jaws go back, and the teeth line waves up and down.

These really conical teeth don't sound very exciting, but they make it different from every other carnivorous dinosaur. No other thing has a conical tooth. It's a classic fish thing, or at least a way of biting and holding onto something that wriggles.

The nostrils are not at the tip of the nose. They're pushed back, at least somewhat. It has a bunch of crests on the head. It's got quite a long neck.

Spinosaurus and at least a couple of its closest relatives—including a thing called Ichthyovenator from—I can't remember if it's Thailand or Laos. I think it's Laos—have this giant elongated bit to the top of the vertebrae, so it gives them this giant sail along the back.

Spinosaurus, at least, and possibly Ichthyovenator, but probably not any of the others, then has this weird, thin, newt-like expanse to the top of the tail, giving it a giant oar-paddle appearance. Mostly they have very large arms with giant claws on the hands. Spinosaurus, at least, appears to have really quite short legs, but the others don't.

But again, Spinosaurus is totally iconic. If you look at something like Baryonyx from the UK or Suchomimus from Niger, they've still got the same head, neck, and arms, but they don't have this sail, they don't have this tail, and they probably don't have short legs. So Spinosaurus is a super-weird and exaggerated version of what was already a kind of super-weird group of theropods.

Spinosaurus is properly strange. And then, as you hinted at, it's super controversial as well, because various papers have claimed it's a diver or a really good swimmer, and I think the evidence for that is very weak at best.

Lex Fridman

So, your book is going to be—you’re going to start some shit with your book. It’s going to be controversial.

David Hone

I think I already have, to be honest. I’ve written 3 major papers, and 1 in particular with my colleague, Tom Holtz, where we frankly savaged the idea that it’s a good swimmer.

Lex Fridman

Oh.

David Hone

Other people have since, including some of the authors who were on the original paper claiming it did swim well, effectively reversed their position and said it didn’t.

Lex Fridman

So, the Jurassic Park III fight between the 2 famous dinosaurs: In a real-life encounter, who wins?

David Hone

Probably still T. rex. I mean, the Jurassic Park Spinosaurus was pretty good for its time because some of the things that I’ve just talked about, particularly the short legs, were suggested as far back as 1910 or 1912, but it was really uncertain. Now it appears to be more likely the case than not. The tail was unknown at this point, so it was just given a very generic tail. But the crocodile-like head is pretty good.

The neck’s a bit short. The sail is a bit too simple; it’s almost just like a semicircle stuck on the back, and it’s a bit more complicated than that. But personally, I’m quite a big fan of the Jurassic Park III Spinosaurus. I think for its era, it’s really quite good. It is massive.

There is this massive pair of jaws, or snout, that’s in a collection in Milan. They’re from, I’m going to say, Morocco, because Spinosaurus is found throughout North Africa: Morocco, Algeria, and Egypt. That points to a truly monumentally sized Spinosaurus, which is where all these upper estimates of 15-plus meters come from: just this 1 set of jaws.

But yeah, it’s about right, but it’s just a bit too muscly and a bit too bulky. In gross appearance, it’s pretty good.

Lex Fridman

Does it have a chance against a T. rex?

David Hone

No. Because it’s got this unbelievably long, thin jaw, which, while much stronger than something like Baryonyx, is fundamentally not that strong. The jaws are very long and thin, and the teeth are big, but they’re not big, big. The whole idea that it grabs the T. rex’s neck and snaps it doesn’t work.

Spinosaurus’s neck is really strong going up and down and very weak rotating, or going side to side. So it’s got the weakest kind of neck possible for rotating and snapping the T. rex, and then T. rex has got the strongest neck of anything. You’ve got the weakest jaw with the weakest spin versus the strongest neck. So no, I don’t buy it.

Lex Fridman

So that brings it back to the topic we touched on a little bit. What are some of the things you’ve mentioned that the Jurassic Park series gets wrong? Maybe you could speak to more things, but also, what does it get right?

David Hone

A lot of very generic but quite important things it gets right. T. rex is about the right size and shape and is massive, and you don’t actually see it run. You see it power-walk. If you watch the Jeep chase again, you’ll see it only ever has 1 foot on the ground.

The weird thing for me is how much some of them vary. I’m a big pterosaur guy. I do lots of work on pterosaurs, the flying reptiles. The Pteranodons in Jurassic Park Two: The Lost World appear very briefly in 1 of the last shots, and they’re okay, but they’re not great. It’s clearly a throwaway shot.

The ones in Jurassic Park III, I think, are mostly excellent—really, really good. And then the ones in Jurassic World are terrible, like a massive regression. There are loads and loads of details that are right in Jurassic Park III that are completely wrong in Jurassic World, and you’re like, “Why did you take a really good model and make it much, much worse and less accurate?” I don’t understand.

Again, it’s fiction. At 1 level, who cares? But I don’t think it would affect how they’re perceived by the public. Some things I get. For example, in Jurassic World, the Pteranodons pick people up with their feet and fly off with them. Pteranodon’s feet don’t work like that. It would never be able to do that, and it would never have the lift. But I get that, for dramatic purposes, you might want to show that. This is your big sequence; you need that. Okay, fine.

But for the rest of the animal, it’s weirdly inaccurate, and I don’t think the public would know, and they might well care if it was much more accurate. I don’t think it would be any harder to make it accurate than to make it inaccurate. I’ve spoken to a colleague of mine, who I won’t name just in case I get him into trouble, who’s a big dinosaur nerd but also a big creature creator and designer and has done a whole bunch of proper Hollywood A-list movie stuff.

I asked him about this. I said, “Okay, but is it just easier to take the model that you’ve got and mess around with it than to, if I came in and said, ‘You need to fix that, and you need to fix this, you need to fix this, you need to fix that’?” And he basically went, “No, it’s about the same amount of effort.”

It’s not like we don’t have the director or the producer or the lead designer going, “No, I want that arm a bit longer. I want that tail a bit brighter. Can you add a few more bits there? I don’t like those scales?” He said, “We’re doing that constantly anyway. So doing it to 1 set of design specs versus another set of design specs is no more hassle.” In other words, he said, “It’s no harder to make it accurate than to make it inaccurate.”

If that’s truly the case, then just make it right. Then you can claim a level of accuracy and engagement that you can.

There’s a thing called the Jurassic Foundation. After the first Jurassic Park made an absolute fortune, I think it was Spielberg directly—it may have been through Universal—but anyway, they set up the Jurassic Foundation. It’s a small fund of money for research on dinosaurs and related animals, and academics can apply for it.

1 of my PhD students got some money from the Jurassic Foundation. That’s great. He didn’t have to do that. He went, “Paleontology’s helped give me this. I’m going to give back a bit.” After what must be 30 years now, it’s probably funded an awful lot of research and helped young researchers get a start.

So there’s a level of engagement there that I think hasn’t been in subsequent films, which you can kind of see once it goes from being a 1-off to being a franchise and it’s changed hands. How many different directors has it had now? Spielberg did the first 2, and then I don’t know about the next 5. It must be 2, if not another 3 more people, and 30 years later, it’s all changing.

Lex Fridman

Yeah, but that’s the path of creating a legendary film. The depth of accuracy—and it’s not that difficult to work on, but it also does something to the whole artistic creation if you create a culture where the details really, really matter.

David Hone

Matter. Yeah, and again, there are some oddities. Gallimimus, which I mentioned earlier, is 1 of the ornithomimosaurs. The model for Gallimimus in Jurassic World is nearly identical to that from Jurassic Park.

1 of the differences, which you can barely see on film, but I know this is true because I found it in a Jurassic World kids’ book when I flicked through it when it came out, is a close-up of the head with an arrow to the teeth. Gallimimus doesn’t have teeth. It’s got a beak.

Someone has taken the original model and actively spent time adding teeth to an animal that didn’t have them. I would understand it. I’m not saying I agree with it, but I’d understand if it was a rule of cool, like, “Yeah, but it would look so much better with all these gnarly big teeth.” You can’t even see it in the final thing. They’ve got tiny little heads.

In the film, all they do is run past the camera briefly. It’s not like they’re a big carnivore and they’re engaged in 1 of the big battles. Why? Why? You can barely even see them.

Lex Fridman

Well, yeah, again, just to linger on it, there is a lot of value to authenticity in all walks of life. When you’re talking about dinosaurs, it’s so valuable and so worthy, and it’s respectable for the long life of a film to be accurate. I just wish—I hope they do that.

There are certain directors that really dogmatically push that. Alex Garland comes to mind. Whenever he integrates quantum computing or AI into a film—

David Hone

Mm-hmm.

Lex Fridman

Nolan, with the black hole in Interstellar, ended up publishing a paper on the calculation to visualize that.

David Hone

I mean, that’s legendary.

Lex Fridman

Yeah.

That’s great. That’s really great. You think that has nothing to do with the story, the narrative of the film, but it does. It permeates everything. If you get that black hole right, everybody else steps up their game and really tells a story in this way that reverberates through time and really moves people.

David Hone

Yeah, I mean, as I say, I wish it was better. The only thing I’d flip it around with is a joke I’ve made more than once: just don’t take it as a documentary. No one watches James Bond and goes, “That’s how international espionage works.” He’s got the laser watch and the exploding car. Maybe treat it a bit as fiction.

I’ve heard from a friend of mine who worked at the Royal Tyrrell Museum, which I’ve mentioned before, in Alberta, which is an absolutely phenomenal place. She said after the first one, genuinely, it was not common, but more than once, people were annoyed that they didn’t have the real dinosaurs out back because they’d seen them and they knew that the real ones were out there.

That’s a testament to Industrial Light & Magic and Stan Winston, but also…

Lex Fridman

Wow.

David Hone

It's slightly horrifying that anyone watched Jurassic Park and literally thought that. Also, why would you go to a museum? You go to the zoo if it's alive.

Lex Fridman

There you will also meet—what is it?—King Kong and Godzilla. I don't think we quite touched on this. I really want to ask you about intelligence. What do we know about the intelligence of, let's say, T. rex? We talked about its big head. What do we know about it?

David Hone

Not much. So there's a T. rex brain, or at least a very rough cast of part of one.

Lex Fridman

Is that the actual look of it?

David Hone

Yeah. So dinosaurs—in fact, most reptiles—I don't know if you can see it on the Velociraptor. Not really, unfortunately.

Lex Fridman

It's elongated.

David Hone

Yeah, but it's more that they have—we are weird in that we have a brain that basically fills the inside of our skull. What most animals have is actually a little kind of sub-skull inside the main skull, which is called the endocast or endocranium, and the brain is in that.

And even then, it's not full of brain because we've packed an awful lot of brain into a limited space, and they then have quite a lot of goo and fat and other stuff around it. But it means for dinosaurs, and then reptiles and birds in general, in the old days you could basically cut one open, but now we'll CT-scan through them. You can take an internal mold of the endocranium, or the brain case, and then whatever filled that would've been the brain and its surrounding tissues.

And that's how you get something like this. In this case, someone literally cracked open an old skull and basically took an internal mold in the same way that you do an external mold for the skulls. And that tells you quite a lot about certain things.

So, for example, they've got a bulb at the front, which is the olfactory bulb. Brains are very stereotyped. Again, ours are super weird, so you have the olfactory bulb at the front, and behind that you have the optic bulb, or the optic lobe. So roughly how big they are will tell you roughly how much of the brain is devoted to, for example, sight and smell. If it's a lot, it's pretty good. If there's not much, it's not very good. That goes quite a long way already.

One thing we've done in the last few years is you can also get into the inner ear. It's not shown here and wouldn't be part of this, but we can CT-scan into the structure of the bony inner ear, and from that you can actually get an idea of what frequency of sounds the inner ear was structured to be pitched to.

Lex Fridman

Wow.

David Hone

Which doesn't actually tell you very much, but it's phenomenally cool that you can do it.

Lex Fridman

We should say you also have quite a bit of a background in biology. So you're trying to reconstruct biology, to go from paleontology to biology.

David Hone

Yeah. My go-to one-liner is, "I'm a zoologist, but I work on dead stuff." My degree was zoology. My official job title now is Reader in Zoology. I teach zoology. I don't teach paleo.

Living animals was always actually my primary interest, and I kind of fell into paleo, but then I wanted to drag that with me because I'd been trained in behavior and ecology, and it's what I was most interested in. So then applying that knowledge and understanding to these animals.

Lex Fridman

So to some degree, it is possible to reach toward the biology?

David Hone

Absolutely, yeah.

Lex Fridman

So with the ear, that's interesting. The brain.

David Hone

Yeah.

Lex Fridman

So we can know something about the brain?

David Hone

Yeah, but then when you get into intelligence is when it gets really awkward, because working out exactly which bits of this are probably linked to the main fundamental processing and what you'd link to actual intelligence is tough.

On top of that, we don't really know. The big challenge of the last couple of years with this question was: were T. rex and other dinosaurs super intelligent? Neuron density—how many nerve cells can you pack in per bit of volume? Birds have some weird tricks, which means they get a lot more brain per volume.

Just how much of the brain case was brain and how much was goop around it, we know varies, so you're getting a fairly big upper and lower band. Then the other big thing we always have to do is factor in size. Big animals need bigger brains to operate them.

So whales have really big brains, but whales weigh tens of tons. They're not smarter than us. The classic thing is a thing called the encephalization quotient. At a very simple level, it is the volume of brain scaled against the size of the animal. We have huge brains compared to how big we are, so we're massively up the chart.

And then you do have a few things with worms. I should probably stick to vertebrates, because there's some stupid stuff which has a surprisingly small brain for its size. Most things that aren't primates—and things like crows and parrots—sit very neatly on a couple of different curves. There's a curve for reptiles, a curve for birds, a curve for mammals, and things like this. Basically, that's it.

But also, our mass estimates for dinosaurs are good but not great. You could easily be out by 20 or 30% on the volume of the brain inside the brain case, and then you could be out by 20 or 30% on your mass estimate. Well, now suddenly, it's very easy to make the brain too big and the animal too light and it's super smart, or make the brain too small and the animal too heavy and it's super dumb. So that's awkward, unfortunately.

Lex Fridman

So apparently there's a controversial paper that suggests that T. rex has primate-level intelligence.

David Hone

Yeah, and then that was shot down within a few months by a team of paleontologists and a couple of other neuroscientists who really went to town on it.

Lex Fridman

Just counting the number of neurons, trying to estimate how many there are?

David Hone

Yeah, it was the neuron-density thing, and, unsurprisingly, I support the revised one—the Casper paper. I've spoken to Casper about it and to a couple of the other authors.

Lex Fridman

So they scaled down the number of neurons from 3 billion to between 250 million and 1.7 billion?

David Hone

Yeah, much, much lower.

Lex Fridman

Which is similar to crocodiles and other primates.

David Hone

Yeah, which is kind of what you'd expect. A couple of other people at various times have suggested they're really smart. Again, birds have this weird thing of neuron packing, and they can basically pack in a lot more than you'd expect. That's why crows are that smart despite having tiny brains, relatively even compared to their overall size.

But I'm being obviously overly facetious. If ultimately part of your scaling is how big the animal is versus how big its brain is, that's the size of a T. rex brain. It's a fraction of the size of a chimp brain, and chimps don't weigh 7 tons. It's a kind of Hitchens-like "extraordinary claims require extraordinary evidence," but you just look at it and go, that's about the proportion we'd expect for a croc.

Now, crocs are smarter than people think, but they're sure as hell not monkeys. You're going to have to come up with something much more convincing than, "Oh, well, if you just pack them in, if you scale them this way."

Lex Fridman

A bit of a ridiculous question, but is it possible to find evidence of tool use?

David Hone

I mean, in theory, it depends quite how you define a tool, so birds building nests is arguably tool use to a certain degree. I'm aware of—I suspect it's turned out not to be the case. I was shown a very rough, not very well-prepared fossil 15 years ago now, where someone said, "We think this might be an early bird nest and therefore potentially even a dinosaur nest," and nothing's ever been published.

So my guess is once they excavated it and had a good look at it, they went, "Nah, it's nothing really." I guess the question is, how would you know?

Lex Fridman

Yeah, it would be difficult unless it's obvious, widespread, primate-like—sapient-like, almost.

David Hone

Yeah, but even then.

Chimps make loads of tools, but it's mostly made of wood, and they're mostly just breaking stuff, and the odds of that preserving are very low. You do get things like chimps and sea otters. They have their favorite anvil and hammer stones to break stuff open.

But again, the reason they picked that stone is because it's really heavy and good at breaking oysters or nuts. It's probably not going to leave stereotypical points on the rock. And even then, you could just go, "Well, maybe it just got bashed up in a river or something."

Lex Fridman

So, in your book "Uncovering Dinosaur Behavior," you conclude that there's a lot we might not know. What's a particular lost behavior that we don't know about that you think might be out there?

David Hone

Something like latrine use. A whole bunch of animals and birds basically crap in the same spot. They have their spot, and that's where they go. Rabbits do this, sloths do this, aardvarks—even things like wildebeest and impala will tend to go back to the same place every day.

But the fossil record of coprolites, fossilized feces and fossilized waste from dinosaurs, exists, but it's extremely rough because, of course, this is the stuff that's already been digested and broken down. It's already kind of gooey and broken up and doesn't have a lot going for it.

If they do it in water, it's going to dissipate instantly. If it rains, it's probably going to fall apart. Things like dung beetles and flies will break it down. Even if it gets covered by sand or whatever from a sandstorm, it's probably still going to compress and separate.

So are you ever going to find it? Maybe. Going back to our trackway stuff, even if you do, what species left that? We know a big herbivore did this, but was it Triceratops or was it an ankylosaur? Those animals are very different things doing very different things, and it would tell you different things about their behavior.

Lex Fridman

Yeah, so one piece of behavior I forgot to ask you about.

So, T. rex engaging in cannibalism.

David Hone

Yeah, almost certainly. Well, certainly. I think we've got a T. rex bone with a T. rex tooth embedded in it, with overgrowth. I want to say it's an Albertosaurus rather than T. rex, but there is a tyrannosaur jaw in Alberta with a T. rex tooth stuck in it, and you can pull the little tooth out.

Then there's a T. rex foot bone with these distinctive feeding traces on it. This actually goes back to that early point about T. rex being weird, being the only big carnivore in its environment. If this was even in Mongolia at that time—or anywhere else—there were 3, 4, or 5 big carnivores. You find a bone and it's chewed up by a big carnivore, and we don't know who did it.

But when you see a big bone chewed up in a T. rex ecosystem, if it's anything bigger than this, you know it was T. rex. So when it's a T. rex bone with T. rex bite marks—

Lex Fridman

Yep, it's pretty obvious.

David Hone

QED. Yeah, so it must have been.

Lex Fridman

That's fascinating, isn't it? That they would attack themselves, their own species.

David Hone

Cannibalism turns up in a whole bunch of stuff, but it's very rare as a fairly habitual behavior.

Lex Fridman

But there are several reasons you might be engaging in cannibalism—or rather, teeth marks might tell various stories. It could be just fighting for dominance, right?

David Hone

It could, but it's unlikely. Again, we see loads of facial injuries in tyrannosaurs, in carnivorous dinosaurs generally, but particularly tyrannosaurs. They have really beaten-up heads. Half or even two-thirds of adults have scarring and facial injuries.

But you see healing on them, whereas this foot does not show healing, and it's got multiple different bites. The idea that you'd bite a foot whilst fighting someone and then go back and bite that one foot again? That's pretty unlikely.

Lex Fridman

So, it looks like it's eating, not fighting.

David Hone

Yeah, and they're more like feeding-scrape traces than they are big puncture wounds. Again, it's not impossible, but it's very weird for that to occur in a fight.

Lex Fridman

So fascinating.

David Hone

Yeah, they're fighting probably quite a lot, but whether or not you actually eat something that you've killed or that you stumble across as a body, it definitely happens occasionally. Otherwise, we wouldn't have a record of it.

There's a reason carnivores often don't eat carnivores, and particularly don't eat their own species: parasitism. Carnivores in general are loaded with parasites because they spend their whole lives eating food that has parasites and other things in it, and so they tend to accumulate a lot of them.

What's the one thing that's definitely going to have the most parasites in it that can infect you as, for example, a lion? It's another lion that eats the exact same stuff that you do. So while it is food, and particularly if you've just won a big fight, you might want to eat it, in general, cannibalism is pretty rare because it's generally not a good idea if there's other food available.

But if you're starving to death, or the other guy ripped your leg half off and you don't think you're going to walk for 6 weeks—not that you'd think, but you know what I mean—and now there's a body in front of you, it's 2 tons of meat. Well, maybe you should tuck in.

Lex Fridman

This is so fascinating, like, once again figuring out this puzzle. What does cannibalism tell you? You're piecing together the story of T. rex—its life, its hunting life, its social life—from its evolution to its biology to its behavior. That's so fascinating.

David Hone

Yeah, we try to. But the thing is, it's always getting better. That's what I tried to finish on in my book on behavior. I felt I'd written a couple of hundred pages of, “We keep screwing this up. We've overstated this. I think people have misunderstood this.” You know, like the trackways stuff: this is not as confident as we think, and you need to look at these alternate explanations. This behavior shows that that behavior probably doesn't correlate the way you said it does.

And then I felt like I'd just written a book trashing my entire field and all my colleagues, or at least many of my colleagues. But then you flip it on its head and go, “We've got techniques that were undreamed of 10 years ago. We've got data streams that were undreamed of 10 years ago. We've actually got a much better understanding of living species.”

On top of that, we're constantly finding new animals. Not just new species, which are often, I think, a lot less important, but new specimens of ones we know, because again, it's building up that database. We drifted off talking about sexual selection, but if you want to know growth, 1 or 2 animals doesn't tell you how an animal, a species, grows. 50 or 100 does.

And then that reveals a hell of a lot more about things like sexual dimorphism, growth rate, how vulnerable juveniles are, population structure, and maybe how they're reproducing. I'd like to think I knocked down a few towers that probably a few people were fond of, but I think we have the raw materials to build a much better, stronger edifice of behavior.

But as you say, it's always going to be based around often very piecemeal evidence, and possibilities and probabilities rather than certainties.

Lex Fridman

Let's talk about a sad topic: extinction.

David Hone

Yep.

Lex Fridman

How did the dinosaurs go extinct?

David Hone

Mostly, probably, pretty quickly. But it really is the answer that I think most people are now probably familiar with: it's an asteroid impact, or some kind of extraterrestrial body, that hit just off the coast of the Yucatán Peninsula in Mexico about 66 million years ago.

It basically atomized the asteroid, but also, importantly, the bit of ground it hit—or below the seabed that it hit—was basically the worst kind of rock. So it put up this enormous ash cloud, and basically you have a nearly instantaneous nuclear winter. There was immediate devastation. Anything immediately next to it was obviously just vaporized.

This is the sort of thing that's hot enough to set fire to the atmosphere. I think the one I read was something like a piece of rock about the size of Mount Everest traveling at something like 10 times the speed of sound. The momentum between that speed and mass is just beyond extraordinary.

Lex Fridman

But I think what does a lot of damage is the change in the climate.

David Hone

Yeah. There are 5 recognized mass extinctions in the history of life on Earth, and all of them are ultimately some form of climate change, whether it's volcanic eruptions, hyperoxygenation, an ice age, or whatever. It's climate changing too quickly for things to adapt to.

That just cripples entire populations and entire species. If you do enough damage to enough things, you start getting ecosystem collapse. This moth has died out. Well, it turns out that moth is the primary pollinator of this tree. That tree produced nuts, and that was the entire winter survival store for this squirrel. That squirrel was the main food of this cat, and now suddenly the moth dying out has killed 4 other things, and everything that's attached to that.

So that's really what did for them.

Lex Fridman

And sadly, the big things—well, everything dies, but the big things have a lot of trouble recovering.

Mark P. Witton

Yeah. This is a classic example. What is paleontology good for? Well, actually, really, it's extinction, which is very relevant right now. We have a very good handle on, when you have extreme climate stress, what tends to suffer more and what tends to suffer less.

As we say, big things fundamentally suffer. They require more resources and more area of land. You need to roam farther, which means if you're a mouse and you happen to have a little bit of land and that bit doesn't get hit, you're fine. Whereas if you're an elephant and you need all of this land and even a chunk of it goes wrong, that's probably not enough for you to survive anymore.

So, yeah, big things suffer disproportionately badly from these things. We also think terrestrial things generally do worse than things in water, because water's a great equilibrating medium. It takes ages to heat up and it takes ages to cool down.

Yes, if you live in specific coastal conditions or something, maybe you can't travel that easily. But whales can go from pole to pole quite happily, and plenty of other fish do too. If it's too hot or too cold or too nasty here, you can just swim somewhere else.

Whereas if you're an animal and you hit a desert, a mountain range, or a river, you stop moving, you're trapped, and then you die. So dinosaurs were the worst possible combination. They were mostly big and they were mostly on land, and it's not really surprising they did very badly out of it.

Lex Fridman

And then some species did survive. I guess I think you've said that it's very possible that some dinosaurs even survived for a time—that we might be able to discover down the line.

Mark P. Witton

I'd be amazed if they didn't. There have been various reports over the decades of dinosaurs surviving the K–Pg, or K–T, extinction—the Cretaceous–Paleogene or Cretaceous–Tertiary extinction—and none of them have held up.

It's usually been bioturbation, so literally things like prairie dogs digging. Of course, they'll dig a tooth up and then move it through the layers. Or things like this, or plant roots can move stuff. Soils can just get churned up.

But I would be shocked if they didn't. Not like, “Oh, yeah, the dinosaur survived, and the Loch Ness Monster,” and stuff like that. But, yes, it was a global devastation.

Yes, it’s what ultimately killed the dinosaurs, but I’d be amazed if there wasn’t some equivalent of Hawaii or New Zealand, or some other tucked-away island or valley, where dinosaurs were actually fine for anything from a few hundred thousand to a couple of million years. But on a global scale, it’s a dot on a map, and the odds that we’ll ever uncover any fossiliferous rocks of that age, have access to them, find a dinosaur in them, and then date it properly—I think that’s almost nonexistent.

It would just be weird if they didn’t survive somewhere for a bit, or even if quite a few of them survived in places.

Lex Fridman

So, a small, local population.

Mark P. Witton

We see it all the time: the lemurs in Madagascar, all the stuff in New Zealand. There’s tons of weird, archaic stuff hanging around in Hawaii, the Galápagos finches and tortoises—the tortoises that you don’t see anywhere else. In Australia, with the marsupials, they’re almost unknown outside of there, and then there are the monotremes.

This is a pretty normal bit of biology. For animals that were so dominant globally, we know there were patches that were largely unchanged. Otherwise, we wouldn’t have had the mammals surviving, and the crocodiles surviving, and the birds surviving, and newts and frogs and everything else that did survive. I’m sure a few of those patches had some dinosaurs in them, but the extinction event ultimately killed them.

Lex Fridman

What do you think is the chance that they would have survived? You take some local populations, and they flourish.

Mark P. Witton

It’s happened. Look at Australia. The marsupials have done pretty well there for a very long time. You can imagine if the next mass extinction flattens a large chunk of Indonesia, for example, kangaroos could island-hop pretty easily and make it to mainland Asia.

Lex Fridman

But then, to take it further, you take the dinosaurs—a small fraction survives—and then they eventually repopulate the Earth again.

Mark P. Witton

That’s extraordinarily unlikely, because once your population has been crashed like that, you do have problems such as inbreeding. Maybe you’re a great specialist to a certain area, or you’re surviving because you’re isolated—you’re in a valley or on an island—and then dispersing again, or breaking out into those areas, becomes much, much harder.

Lex Fridman

So, the great predators, like the T. rex—even though the T. rex is such a great predator, that doesn’t give you—

Mark P. Witton

You still had the extinction event, and the environment is no longer what you evolved into.

Lex Fridman

Right.

Mark P. Witton

Once those systems start to recover, those other animals are going to adapt much better to them.

Lex Fridman

How does that make you feel—that this stupid asteroid came from nowhere?

Mark P. Witton

At one level, I probably wouldn’t be here if it hadn’t.

Lex Fridman

That’s an interesting question. There are several ways of asking it, but if dinosaurs didn’t go extinct, do you think humans would still have been able to evolve?

Mark P. Witton

My guess is probably not. I don’t think it’s quite the idea that Simon Conway Morris proposed in What was it? Oh, Simon Conway Morris had that book. What was it? Inevitability of Man. That, like, even if you rewound it, everything would come back. I don’t think it’s that far.

I certainly don’t think it’s anything quite like the butterfly effect: if one mammal had been trodden on by one T. rex, then humans would never have evolved either.

Lex Fridman

We should say that the ancestor of the primates—or the closest thing to it; there’s a lot of debate around this—is a tiny creature, Purgatorius, that was our ancestor. This is us. This is what we evolved from.

Mark P. Witton

Scandentia, I think, is the group.

Lex Fridman

Basically a rodent.

Mark P. Witton

There were probably primates around in the Cretaceous. Some of the molecular-clock evidence suggests that primates were around alongside the dinosaurs, but we’ve never found any osteological evidence of that.

There’s been a back-and-forth about whether dinosaurs were already on their way out, or whether they were somewhat limited by the very end of the Cretaceous. I think the more recent analyses have shown that’s probably not the case. In other words, they were basically doing fine right up to the extinction event.

If the asteroid hadn’t hit, there’s no reason to think that they were on some kind of terminal decline. Something else may have hit. There may have been some other environmental disaster, or something else may have happened, or maybe they were more vulnerable to things than we know. But I don’t think there’s any really good reason to think they wouldn’t have carried on relatively well.

Even after the dinosaur extinction, you had a window in which the mammals and the birds were competing. There were a lot of big birds getting going, along with various big, carnivorous, terrestrial, hyperpredatory, ostrich-like animals, such as the phorusrhacids. So there’s no guarantee that mammals would have even taken over after the dinosaur extinction, since initially they were in a fair bit of competition.

Lex Fridman

So, based on current scientific understanding, human evolution would be highly improbable if dinosaurs hadn’t gone extinct 66 million years ago, because dinosaurs dominated ecological niches.

Mark P. Witton

For everything, basically.

Lex Fridman

Warm-blooded mammals?

Mark P. Witton

That’s the thing. You look through the Mesozoic, the Late Triassic, and dinosaurs are there alongside a whole bunch of other big, unusual, interesting reptiles and some other early, premammalian things that are closer to mammals than to reptiles.

But once you’ve gotten into the Jurassic, you’ve now got a solid 120–130 million years where, almost anywhere on Earth, if you saw an animal bigger than a raccoon, it was probably a dinosaur. That’s how incredibly dominant they were—at least as dominant as, if not more dominant than, modern mammals.

Lex Fridman

But is it fair to say that they were mostly dumb?

Mark P. Witton

I don’t think so, because that comes down to a bit of classic, almost Victorian speciesism. You get these insane hypotheses, like the idea that dinosaurs as a species or as a lineage became senile, so they forgot to breed. There’s the idea that mammals ate their eggs, and all of this kind of stuff. Dinosaurs lived alongside mammals for 100 million years. It would be weird if they all went extinct at the same time because egg-eating suddenly evolved.

But there’s also that general speciesism, which goes back to Linnaeus and his taxonomic ranks, and arguably even to Aristotle. You get this idea that humans are superior in some way, and we’re superior to the other mammals. Of course, mammals are closest to us, so they must be quite good. Then they must be better than lizards, lizards must be better than frogs, and frogs must be better than fish.

That gets you into the idea that reptiles must be stupid. They’re not.

Lex Fridman

I wonder if a human-level intelligence organism could have evolved from the dinosaurs.

Mark P. Witton

That’s been hypothesized plenty of times. Dale Russell, a Canadian paleontologist, came up with the famous human-like troodontid for a television documentary—I think the one Christopher Reeve narrated. That was a remake, but I’ve seen the original that Dale made for his television show, and it’s still sitting in the collections of the National Museum of Nature in Ottawa. It’s really, really cool. It’s a five-foot-tall dinosauroid.

Lex Fridman

“Model of the hypothetical dinosauroid on display at the dinosaur museum in Dorchester.”

Mark P. Witton

Oh, Dorchester. That’s in England. I knew there were a couple of copies of it.

Darren Naish

Troodon always comes back as the most intelligent dinosaur because it has a really big brain for its size. It does have a high encephalization quotient, so it’s always been tagged as a very good candidate for being the smartest dinosaur. Basically, Dale Russell just hybridized that with a human.

But why would these things end up as plantigrade quadrupeds? Why would they go back to five fingers? Actually, I think he’s only got three, to be fair, but he’s got very human-like feet. Why does it have no tail? Why would those things suddenly disappear? There’s no real reason other than human exceptionalism.

You could argue that some parrots and some crows are phenomenally intelligent and show extremely clever behaviors on par with apes. At some level, some dinosaurs were extremely intelligent.

Lex Fridman

This is a whole other conversation, but all the tiny details that lead to the explosion in our evolutionary tree that is Homo sapiens—what is it? Opposable thumbs, right? Is it the invention of fire and meat-eating?

Darren Naish

Fighting and sociality.

Lex Fridman

So many.

Darren Naish

Predation pressure, and then the changing environment. The shrinking of the forest pushed apes out of the trees into the open environment.

Lex Fridman

And probably the same kind of story could be told about the dinosaurs, or about anything, really.

Darren Naish

If you have 160 million years and global domination, that’s the thing. You talked about lost behaviors, but there are also the lost lineages. I wrote about this in one of my books, and if you want to find a weird animal, you go to a volcanic island. You go to New Zealand, Hawaii, or the Galápagos, and yet those are the places that basically don’t really form fossils.

You think the dinosaurs we know about are strange. What was the stuff knocking around there? We’re never going to know, sadly. But for everything you think is weird, you know, you think birds are cool—think about penguins compared to your average bird. They live on an ice shelf for 6 months of the year, can’t fly, and have massively modified skeletons.

You know, compared to your average bird, penguins are unbelievably weird. So yeah, take an average dinosaur and take it to penguin-level, ostrich-level, or hummingbird-level evolution. There’s going to be weirder stuff out there than we’ve found. Much weirder.

Lex Fridman

If you travel back in time, your mind will probably be blown by the weirdness.

Darren Naish

Yeah. Because those things are almost always in small, isolated places that don’t preserve fossils very well, so the odds of us ever coming across them are low. I mean, you see it to a degree. So you’ve got the stuff that comes out of what is modern Transylvania—what was Hațeg. That was a series of islands in the Mediterranean at the end of the Cretaceous, and some of the weirdest dinosaurs are from that chain of islands.

That’s not very isolated compared to something like Hawaii or New Zealand, but it’s fitting the exact pattern. You get dinosaurs on islands, they turn weird. We see that.

So again, dinosaurs were real animals. Again, it sounds really painfully obvious, but they weren’t monsters. They followed the same—rules might be pushing it, but certainly guidelines. Ecology operates in certain ways. If you’re bigger, you need more food, but you’re more efficient. You just are. That’s pretty much just physics and scaling.

So big dinosaurs are going to follow the rules of bigger animals, and small dinosaurs are going to follow the rules of smaller animals. They just will. Quite how they violate those rules in certain ways, by having unusually long necks or unusual physiology, eating an unusual diet, or because there was a weird plant alive then that isn’t now, or whatever it may be—there’s obviously a huge amount of variation and uncertainty.

But fundamentally, we know what makes animals and ecosystems work, and dinosaurs were animals in ecosystems. They’re not that strange at some level, and therefore reconstructing their actual biology is challenging, but far from impossible.

Lex Fridman

Strange question. As everybody knows, dragons are obviously real.

Darren Naish

I’ve been asked that on live TV before, only not with the sarcastic tone.

Lex Fridman

Do you dare disagree with this notion?

Darren Naish

Yes, I do. They don’t.

Lex Fridman

Well, they’re real to me, so—

Darren Naish

That’s fine. But again, we kind of touched on it, but I think there’s probably very little, if any, paleontological lore that ended up in things like Chinese culture, with the Chinese dragons and all of that stuff. That one comes up repeatedly.

The only one I do know of, again from Alberta, is buffalo stones that apparently some of the Native Americans had, which are actually bits of ammonites. Ammonites are curly, spiral-shelled cephalopods that are related to octopuses and squid. They have all these little segments to their shells, and the right species, when they break open, have two little pairs of legs, then a bulge, and then a little bulge, and it looks very roughly like a bison.

Apparently, these were thought to be somehow miniature bison. They’re very rare because, ironically, although the dinosaur bones are extremely common, it was very swampy, so you didn’t actually have a lot of sea coming in. You didn’t tend to get things like ammonites and other ocean-going animals. Then the shell would have to break in the right way.

But apparently, for the local tribes, like Sáptəṉilh [?]—I don’t remember who it is in that bit of Canada—these were quite valued. If you’ve got a buffalo stone—and I’ve seen a couple of them—yeah, you have to squint a bit, but as a little buffalo, it’s not far off.

But that whole question of whether they were finding mammoth legs, whether they were finding T. rexes, and whether this was inspiration for this animal or that mystical animal—I don’t think they were, because you just don’t tend to find them like that.

Lex Fridman

So where do you think—because dragons show up in a bunch of different myths—

Darren Naish

Well, right. But that’s the thing. They turn up in British mythology, and we’ve barely got any dinosaurs here at all. You only find them when you start digging for coal mines, which we weren’t doing—

Lex Fridman

Is it basically a dramatization of snakes and lizards and stuff like this?

Darren Naish

Yeah, and just general exaggeration and welding stuff together. I mean, that’s one thing you could potentially argue. We find tyrannosaurs in North America and in East Asia. In fact, there’s a whole bunch of stuff in the Early Cretaceous, which is often very common because it’s all relatively recent, in the grand scheme of things, in the history of the world.

The fauna of East Asia—China, Mongolia, and eastern Russia—is very similar to what you get in Canada, the USA, and down in Mexico. You find the same rough stuff. They may not be exactly the same, but you get ceratopsians, you get tyrannosaurs, you get the big-edged archosaurs, you get ankylosaurs, the armored ones, this, that, and the other.

So if these were influencing all those different cultures, why don’t Chinese dragons look like Mexican dragons, or equivalent thunderbirds, or whatever? Well, because it probably wasn’t influencing them. If they were all seeing the same skeleton, they’d probably all produce the same kind of mythical animals. They all produce—

Lex Fridman

Well, uh—

You have to understand, paleontology’s not perfect, so they were just misinterpreting it.

Darren Naish

Misinterpreting, yeah.

Lex Fridman

I mean, dragons aside, I’m sure, like we said with weirdness, there would be creatures that would be remarkable. You look at them and you might as well be seeing a dragon. And I mean, there are creatures alive in the sea today.

Darren Naish

Yeah. If you dredged up a colossal squid, I think you’d have— Even just dugongs and manatees. I mean, they’re really quite strange.

Lex Fridman

And if you allow yourself to marvel at the small things on Earth, like when I was in the Amazon jungle—the insects—they’re just like, “What is happening there?” There are so many things going on. They’re hairy and colorful, probably poisonous, and they have teeth. What? And they’re long and—

Darren Naish

Well, and all the little weirdos. Several times, I’ve pitched a book to publishers that basically makes the point that there is almost nothing—I mean, you can always dream up something totally ludicrous—there is basically nothing in science fiction that doesn’t already exist on Earth in some way, shape, or form.

Lex Fridman

Yeah, that’s why I think about alien civilizations and aliens out there. I’m very, very certain that there are aliens everywhere throughout the observable universe. It’s very strange that we haven’t seen them, but it’s fun to marvel at what they possibly look like, because there’s a huge variety of organisms and species here on Earth. You just expand that out to more and more Earths, and you can just imagine there’s a lot of weird—

Darren Naish

Well, that’s the thing. I think most people, understandably—I’m a biologist, and I particularly pride myself on finding out about particularly weird animals—but I think people would be stunned by some of the weird stuff that’s out there that they just wouldn’t realize is real.

Things like velvet worms—it’ll blow your mind. Caecilians and their reproductive behavior are just jaw-dropping. I love teaching about them. I do a class on diversity of life, and it’s about 8 weeks of vertebrate diversity. I love just dropping things in, and the students are like, “What do you mean that exists? What do you mean something like that’s normal for this group?”

Yeah, they do that.

Lex Fridman

What from that class—and from everything you’ve studied with the dinosaurs—have you learned about the evolution of life on Earth, that mechanism?

Darren Naish

It’s really good. It sounds obvious, but I think the bit that still fries my brain is just the raw numbers, because I think we’re very bad at considering them. I regularly talk about, “Oh, this is 70 million years old, but this is 78, and this is 104,” and people are just like, “Oh my God, how on Earth do you deal with those numbers?”

They’re just numbers, because I can’t conceive of them really any better than you can. They’re astronomical. Yeah, last Thursday was quite a long time ago. Sixty-six million years is mind-boggling. I can’t fathom it. I can’t fathom it.

But that’s it. I think the evolution thing is—my suspicion is quite a lot of it happens during stressful events. It’s not quite Stephen Jay Gould’s punctuated equilibrium, but I think stressful events probably prompt a lot more than less stressful events. Population crashes and all these things mean that odd things survive, and then that changes your genetic component and all the rest of it.

But you’ve just got to remember that it’s almost a numbers game. You know that bad analogy: “Oh yeah, evolution is just rolling dice and hoping you get all sixes.” A friend of mine said, “No, it’s rolling dice, but it gets to keep the sixes.” Suddenly, getting a hatful of sixes isn’t that hard.

But you’re also in the context of even rare species—ultra-rare, short of stuff that we’ve nearly killed off—having populations in the thousands or hundreds of thousands, and probably being around for hundreds of thousands of years. Very few, other than a few things like whales, apes, and elephants, mostly have dozens or thousands of offspring at a time.

So a few thousand animals that have a few thousand offspring, alive for a few hundred thousand years—yeah, it’s billions and billions and billions of them. And that’s the rare stuff.

You look at Mola mola, the ocean sunfish, though I think Mola has just been split up into about 5 species. It’s one of the weirdest-looking animals. I love it, love it, love it. I mean, what a fish that is.

Swims with a giant dorsal and, I think, a giant anal fin, and then they flap alternately.

Lex Fridman

Does it have a face?

Darren Naish

Yeah, yeah, yeah. Little one at the front. It ate jellyfish. Super open-oceanic. And they get really big. You can see that one with the diver. But I think these are the record breeders for animals, and they have something like 100 million eggs at a time.

Lex Fridman

Whoa.

Darren Naish

Don't quote me on that, but it is something in those kinds of numbers. So you don't need a very large population of sunfish to start having an awful lot of numbers.

Lex Fridman

Are you going to Google it and see if you can find it—number of eggs or something?

Darren Naish

Yeah. 300 million. Oh, I undercut it.

Lex Fridman

A single female can release up to 300 million eggs at one time during a spawning event.

Darren Naish

I undercut it.

Lex Fridman

A single female can release up to 300 million eggs at one time during a spawning event. Boy. These eggs are incredibly small, measuring about 1.3 millimeters in diameter.

Darren Naish

That's still a lot of egg size when you think about it.

Lex Fridman

It's not that small.

Darren Naish

Yeah. 300 million of 1 millimeter is still quite a bit. Fertilization is external.

Lex Fridman

Yeah.

Darren Naish

Females release their eggs into the water, where males then fertilize them.

Lex Fridman

Wow. Man, there's a lot of different ways to have sex, I guess.

Darren Naish

Yeah. But that's the bit of evolution that I think—I understand why people don't get it. We are mostly talking about millions in population times millions of years times thousands of offspring. It's kind of a numbers game.

Lex Fridman

Well, how could this evolve?

Darren Naish

With the right selective pressure, and when you've got 100 billion offspring, probably a few of them have that.

Lex Fridman

And when you focus in on a single species and trace its history, you can see how effective evolution, natural selection, is. Then you just have to go across species and realize—

Darren Naish

Yeah, but it's also a massive compromise, which is the bit that people always miss. You know, it's Darwin's line: “It's descent with modification.” Yes, over time, you can end up with extraordinarily weird things, but mostly what's happening is you're changing something fairly simple.

You're making edits to the existing plan, which is why you don't have animals with tentacles. They have legs, which have joints, which have fingers, and they all have 1 bone, then 2 bones, then a bunch of little blocky bones, and then a few more, and then the little ones that make up the digits for hands and feet. Basically everything has that because you're modifying that pattern.

Occasionally you'll get something weird, like most of the modern lungfish have basically reduced those down to—well, they had a more simple plan to begin with, but reduced it down to a stump, and then they've got something like a flaily tentacle. But snakes have gotten rid of them, as have all the various legless lizards and things like that, and again, caecilians and all the rest.

You're subtly changing certain things in certain ways. That's mostly what's going on, and then those changes build up over time. But, again, it's that compromise of there being things that do and don't work. There are things that are interlinked, so you can't modify A without modifying B. Modifying A will kill you; therefore, B never modifies, because the two are genetically linked in some way.

Or, like the compromise of the lion's mane: making it darker makes you sexier, but more likely to kill you. I think people think evolution is about perfecting things in some way. They're not. They're bodge jobs, you know? That's why we have a blind spot in our eye, but things like squid don't.

Lex Fridman

But that process, nevertheless, does have inventions in it. You have Tiktaalik. You have a fish that learns to breathe, that crawls out.

Darren Naish

Yeah, but it already had a swim bladder that it was probably processing a minimal amount of oxygen through, and the swim bladder evolved for a different function.

Lex Fridman

Yeah, but that's one of the powerful things about evolution. It switches the function. It develops it for one function, but once you get there, you're like, “Oh, okay, this could be used for another function.” That leads to something that we, in retrospect, can see as a major invention, which is a fish that's able to crawl on land. All of a sudden—

Darren Naish

Yep, absolutely.

Lex Fridman

—we have cities and rockets. Tiktaalik specifically, there's something really mind-boggling about a fish that crawls out of the sea, and you just have the image of that.

Darren Naish

Yeah, but, again, you've got stuff that's not a million miles away from that. You have things like frogfish, which are fully marine, but kind of clamber through seaweed and stuff, and they've got pseudo-functional limbs. Again, Tiktaalik is not a weirdly derived frogfish, but it's not like it's a fish that suddenly came on land or a fish that suddenly evolved legs. There was already that selective pressure that was pushing it into a new opportunity, which gave it an advantage, and then on and on and on. That's what keeps going.

But it also brings up another thing, going back to dinosaurs and the behavior stuff, which, again, I think has been a problem: the functionality thing, and how there's always been this big perception of single traits having single functions, which isn't how a huge amount of biology works.

For some things, yes. Eyes are used for seeing. They don't really do anything else. But I think there's a lot of—again, it comes down to a lot of the sexual selection stuff. Things like horns on Triceratops are probably quite good for fighting off predators, but they're also quite good for fighting other Triceratops.

Things like elephants dig with their tusks, as well as fight other elephants, fight lions, and strip the bark off trees. So you've got to be very careful about how you think of functionality in 2 different ways. One way is: What possible things could that thing do, and what possible things could have been the main selective pressure before?

So you think about elephant tusks. As I say, they do all these different things. But when an elephant's just got the tiniest little nubs—like the first elephant whose teeth are growing the wrong way and have pushed out of its jaw, and now it's got a couple of little spikes—it can't really dig a hole with them. It's certainly not digging for water. They're probably not great against a predator, because you'd basically have to get on your knees, lean over, and try to stab it a bit.

But you can show off to the girls, and you can immediately find another elephant who's head-to-head at the same height as you, and you've got a massive advantage. So evolutionarily, they probably started as some kind of sexually selected feature.

But now, functionally, they are probably compromised by the fact that having the best fighting tusks, but also having the tusks that are best at digging up water to keep you alive during a drought, is putting selective pressure on that. Those are 2 selections. Sexual selection appears at both ends. Those are 2 different things. Digging for water is critical, but it's probably not what started it.

I think that's where we get trapped with things like the paddle tail of Spinosaurus or T. rex arms. It's like, “Why are T. rex arms like that?” Maybe we need to consider what a slightly longer arm is like, what it was functioning for in its ancestors, how it works in other species, or what else it might do, rather than every paper asking, “Did it do this?” or, “Did it do this?” or, “Did it do this?”

It could be all of them. That's a very different question to try and answer, but people don't tend to think of it. It ends up being very binary. Again, biology is not like that, because it's a compromise.

Lex Fridman

It may be wiser, then, to look at the evolutionary origins—how it first sprung up.

Darren Naish

Yeah. What does a miniaturized version of this look like, and what might that function for? Or how does it function in ancestral forms?

A really good example of that is giraffe necks, which have been argued about forever and a day. It was, “Giraffe necks are to help them feed up high.” Then, in the late 1990s and early 2000s, there were a couple of papers coming out saying, “Actually, maybe it's sexual selection and competition.”

Mark Witton

That drove down into arguments about, “What does a short neck look like?” The okapi is the nearest relative. “What do short legs look like, and how do they work?” Plus a whole bunch of other studies. Ultimately, it came out that we were right the first time: This is all about feeding.

But it's a really interesting way of thinking about it and looking at it.

Lex Fridman

I've got to ask you the ridiculous question. We do have dinosaurs here on Earth today. They're birds.

Mark Witton

Yep. There are 10,500–11,000 species of dinosaur.

Lex Fridman

Are birds dinosaurs?

Mark Witton

Yes.

Lex Fridman

Yeah, it's wild.

Mark Witton

It's just a yes.

Lex Fridman

Yeah. How many people know this, by the way?

Mark Witton

There's an interesting one. I did a radio show probably 7 or 8 years ago now with a couple of presenters—you know, drive-time afternoon, nothing serious, nothing science-related or anything like that. I mentioned something like this, and one presenter was, “Oh my God, what do you mean birds are dinosaurs?” And the other one was, “What do you mean you don't know birds are dinosaurs?”

So it's hitting that tipping point of common knowledge, I think. Does everyone know? No. But I think an awful lot of people know and are now used to it as an idea.

Lex Fridman

So what's the evolutionary connection between birds and dinosaurs?

Mark Witton

They literally are, in the same way that we are apes and mammals. Birds are dinosaurs.

The direct connection, if you trace back the evolution of all the birds—hummingbirds, albatrosses, ostriches, kiwis, parrots, pelicans, penguins, and whatever else—and take them down to their ancestral point, and then go back quite a few more million years, their nearest relatives are dinosaurs.

It is actually something very close to Velociraptor, or at least a small version of Velociraptor. So birds have literally descended from dinosaurs; therefore, they are dinosaurs. We have literally descended from other apes; we are apes. It is that form of evolutionary connection.

Lex Fridman

Throughout that whole process, did they have feathers, or did feathers come and go?

Mark Witton

Feathers are in tyrannosaurs. Feathers go back at least—so, ironically, because the fossil record is very incomplete, most of the things that are closest to birds are known from the early and late Cretaceous, the last kind of 50 million years of dinosaur evolution, up to the extinction. Birds almost certainly go back another 50 million years.

Birds did not appear as a result of the dinosaurs going extinct. Birds lived alongside the dinosaurs for 100 million years. The birds were not new on the scene. It's not like, “Oh, the dinosaurs died, and from the ashes rose the birds.” No, they've been knocking around forever.

Lex Fridman

They just survived because they're small.

Mark Witton

In a very large part, yeah. That's almost certainly what really helped them. Birds took a kicking in the K–T extinction. So did mammals. Loads of bird lineages went extinct, and only a handful got over the line, but they did.

We have feathers. As I said, we've got Middle Jurassic tyrannosaurs that are 165 million years old, so 100 million years before the extinction, that have feathers. Simple feathers—they'd be like those you get on most baby chicks. They're not the big, classic feather you pick up in the street or on a field, with the big vein up the middle and the paired flat pieces. This would be much more like a hair. But we have them.

We've got something which is very close to a bird, but might not quite be a bird, with modern feathers. In the Middle Jurassic, we've got definitive stuff like Archaeopteryx in the Late Jurassic, and then into the Early Cretaceous we have a series of fossil beds in China which are just heaving with them.

Tyrannosaurs have feathers. Velociraptor and the dromaeosaurs had feathers. Troodontids had feathers. Ornithomimosaurs, which we've mentioned, had feathers, and so did a whole bunch of other groups as well.

There are about 8 or 9 major groups, literally like carnivores or deer—some massive groups. About 8 or 9 of them were fully feathered, as far as we can tell. So feathers massively predate bird origins, but they were a major part of their evolution.

Lex Fridman

Do I understand why feathers evolved, with the function of sexual selection and signaling?

Mark Witton

Yeah, it's probably a fundamental twofold function. Feathers insulate you. They keep you warm. Most dinosaurs were—it's an archaic term, but it's what most people know—warm-blooded. So they were much more like us and birds. They had a stable, high body temperature regardless of the environmental conditions.

If you're burning a lot of calories to stay warm, you want to keep that heat, and feathers really help you do that. The other thing is the obvious one: sexual selection and communication. Feathers do stuff that scales can't. You can shed them in winter, change color, and come back as another one. That's quite a handy trick.

You can change them between juveniles and adults. Baby birds have one type of feather; adults have a different one. We know of dinosaurs that do that, where we've got adults and juveniles with different feather types preserved in the fossils.

You can produce all kinds of weird colors and displays. You can erect feathers. You can hold them up and fan them out like a peacock or a pheasant. Whereas with scales, you can't really do that, or you need a huge amount of bone like Protoceratops.

So there's two good reasons that they would probably evolve, and it's difficult to pull them apart or say which is more important. Again, they're probably bifunctional. As soon as you start making feathers and making them more colorful, well, you're staying warmer. So that's an advantage.

Or as soon as you start making feathers to make them warmer, it probably won't be long until someone evolves them to be a bit brighter red. Then we're back to, “Oh my God, red.” Right? But that's what's happening. They're probably going to push each other, potentially.

Lex Fridman

It is true that the birds went real crazy with feathers and the colors and the prettiness and all that.

Mark Witton

They absolutely do.

Lex Fridman

Maybe there's something about feathers that allows for that efficient diversification of fashion.

Mark Witton

I think it gives them opportunities that scales and solid structures simply don't.

Lex Fridman

Yeah, it could be a material for it.

Mark Witton

Peacocks and pheasants are at a massive disadvantage, and males have got these extra plumes because they're so big and heavy. Peacocks can barely fly. But the fact is, you can still fold them up into a fairly neat package and hide if you really wanted to.

Whereas if you're something like a Triceratops, that billboard stuck on the top of your head is not only enormous but also bone. It's massive, it's heavy, and you've got to—

Lex Fridman

No hiding.

Mark Witton

—hide it around the whole year. Whereas peacocks at least can go, “Well, all the girls have settled down on their nests now, so I'm just going to get rid of all this extra weight and dump it.”

Lex Fridman

Just looking at the entire history of Earth, what has studying hundreds of millions of years of evolution, studying this epic age of the dinosaurs, done for your appreciation of what makes Earth beautiful? Do you ever just sit back and think, “Holy shit, this is incredible, this whole thing”?

Mark Witton

Yeah, I do. But I guess maybe not much more so than I would anyway. I don't really think of myself as a paleontologist in a lot of ways. It's not that I don't love my work, but I'm a biologist, and this is what I'm looking at.

I'm fascinated and amazed by lungfish and flying frogs and caterpillars and onychophorans and butterflies and a million and one other hagfish and things that I think are cool and interesting and fascinating. I could happily read about them or watch them in a zoo or a documentary or whatever it may be, almost every bit as much as I would with dinosaurs.

I probably appreciate the dinosaurs and pterosaurs in a very different way because I have such an intimate knowledge of the science. I try to read the lion literature because I'm really interested in predation dynamics, but I can't keep up with it while doing all the other stuff as well.

Lex Fridman

Predation dynamics. Awesome.

Mark Witton

Well, right, so the difference is: What prey are they taking? Why? At what percentage? What influences it? How are they competing with leopards and—

Lex Fridman

Wait, there's a body of literature on this?

Mark Witton

Yeah, people are studying lions—what they hunt, what they eat, and where they do it. There's a whole bunch of stuff on particularly the African carnivores, because there are so many of them and they're so big, and their populations aren't terrible compared to South America, North America, or a lot of Asia, for example.

Going back to your question, I can appreciate all of it. It's all cool. Some of it is definitely more awesome than others. I work on some of the giant pterosaurs, the ones with 10-meter wingspans.

It's hard. My partner's family is from Uganda. We were in Uganda last year. I was watching marabou storks circle overhead, and you're like, “Wow, these things are huge and amazing.” Then I'm like, “Their wingspan is about a fifth of the stuff I work on.”

Actually, these are quite piddly in the grand scheme, you know, this thing being like an airliner going overhead. Because that's it with the— I know people tend to be obsessed with size. You get it: blue whales are fundamentally cooler than smaller humpback whales, even if humpback whales are cool.

It's hard not to be impressed by Patagotitan or Tyrannosaurus or Triceratops or Quetzalcoatlus or any of these ultimate giants. There's a reason we love great white sharks, there's a reason we love giant squid. There's a reason we love lions and grizzly bears and stuff.

But the dinosaurs do kind of do it better than anyone else, as do marine reptiles and flying reptiles, because it's just so insane.

Lex Fridman

Yeah, both size and diversity.

Dave Hone

And longevity as well. You look at elephants, they've come and gone. The whales have reached superlative sizes, but they're relatively new on the scene. They could easily have gone extinct in the last century. But yeah, there have been truly titanic dinosaurs for at least 100 million years.

Lex Fridman

It's a long time. It's hard sometimes, as you said, to load in just how long that is. They really dominated Earth for a very long time.

Dave Hone

Yeah, and almost absolutely everywhere. There's a handful of places that we've found where it appears that dinosaurs didn't really get in, and something else kind of took over, like Australia with the marsupials versus the other eutherians.

But yeah, fundamentally, it was a dinosaur planet. After the Triassic—less so at the end of the Triassic, when they're first getting going—but the Jurassic and Cretaceous were 140-ish million years of absolute dominance.

Lex Fridman

I think it's hilarious and just perfect that there's a giant dinosaur head next to you, and you didn't mention it once during this conversation.

Dave Hone

Because I thought we'd get to it. I mean, giant is an absolute diddy one. This is Protoceratops andrewsi. I've done loads of work on Protoceratops.

It's from Mongolia. This is a little one, so I've got a big head, and the big head's kind of like this, but I really couldn't fit it in the bag.

Lex Fridman

So this is a to-scale juvenile.

Dave Hone

This is a cast. This is not original, but someone has molded and copied it. So it's not even carved; it's a cast from a mold. This is 100% accurate to the original specimen, or at least extraordinarily accurate to the original specimen.

Lex Fridman

So it's a young guy.

Dave Hone

Yeah. At full size, it's going to be about pig or sheep size, so big but not massive. But I've got it partly because it's affordable, because I can't afford to buy the big skeletons and skulls. I've done a huge amount of work on it, and in part it goes back to those earlier conversations about populations.

If you really want to understand animals, you need an understanding of what a real population and the growth of these animals look like. Protoceratops is, I would argue, probably the only dinosaur where we can really do that, or at least get as close as possible to any modern animal as an analog. We've got well over 100 good skeletons, though probably only about 70 or 80 in really accessible museums, but that's still a hell of a lot.

We have everything from, “Here’s a tiny baby one.” This is a really cheap and nasty 3D print I had made, but that's a hatchling-sized one, or not much bigger than a hatchling-sized one, all the way up to the big adults. We've now got embryos as well, which we didn't have until about 10 years ago. So we've got embryonic animals all the way up to big adults.

They're all pretty much from one place in Mongolia. And they are, as far as we can tell, from a relatively narrow window in time—only about 100,000 years—which in the grand scheme of things is very close. So you've got 1 population from 1 place, from 1 time, with 100 animals from embryos up to big adults.

Lex Fridman

That's okay.

Dave Hone

So now if you want to look at, as I do, something like sexual selection—when does growth of the signal kick in and at what size, and what evidence for dimorphism?—well, suddenly you've got a population. You've got something you can work with. That's why Protoceratops is so important, and I think way more important than even a lot of my fellow paleontologists realize.

I genuinely think we should be pouring a lot more research into them, because they can tell us stuff that pretty much no other dinosaur can.

Lex Fridman

Because you have the population data, so you can ask them a lot more questions.

Dave Hone

And we can treat it as a population. Going way, way back to a conversation about telling males and females apart, I said the big problem is population data, or at least the number of specimens that you have, when mostly you've only got 1, 2, or 3.

I did a big study on this a few years ago on gharials, the really long-snouted crocodilians from Nepal, India, and Pakistan, with a giant bulge on the end of the nose. Even though the males are all bigger than the females, and the males all have this weird nose growth that's mostly soft tissue, they have a weird depression in the jaw at the end of the snout, where the nostrils sit.

We got a sample size of something like 110 animals. These are very, very rare animals, so we had to ransack every museum worldwide. I was sending my students emails to huge numbers of people: “Have you got one sitting lost in your collection? Can you get it for us? Can you take these photos or these measurements? We can measure it.”

We put the dataset together, and then we found that actually, apart from the very biggest males, it's really hard to tell males and females apart. This closely matched some modeling data that I'd done with a colleague, Jordan Malin in Ottawa, looking at this for alligators and trying to compare it to dinosaurs.

Because we talked about mutual sexual selection before, and under mutual sexual selection in particular, you tend to get things that are extremely similar. Males and females are very hard to tell apart. But there's also a gradient, all the way up to things like peacocks, all the way down to things where you can't tell them apart, like parrots.

For some features, when they take time to get growing, or because dinosaurs grow over a very long window and are sexually mature over a very long window, you run into the problem that a big female will look like a small male. We can't sex them, and lo and behold, this is what you get with the gharials.

The really big males are obvious because they're so much bigger and they've got this big depression in the snout, but medium-sized and big females look like medium-sized or smaller males and very small males. And so, yeah, that's basically what we have with dinosaurs.

Even with Protoceratops, where we've got a dataset of about 100, papers have come out saying there's very mild sexual dimorphism, or there isn't sexual dimorphism. Sexual dimorphism could be very strong in Protoceratops, but we can't find it because we can't tell the males from the females, because we haven't identified enough of them through something like medullary bone.

And so you're in this horrible situation where, going back to the T. rex thing, it's like, well, maybe it's mutual sexual selection and therefore they're cooperating, and that would be cool. But also, maybe males are much bigger, and we can't tell because our dataset's too small.

Lex Fridman

Oh, that's frustrating.

Dave Hone

Argh! It's maddening because if these were living animals, you'd just watch them, or you'd just genotype them, or you'd sex them, and you'd just know. And we just don't.

But on the other hand, we do have the mechanism to do it. There are a handful of places where you get a bunch of Protoceratops together, where it's a mass mortality site. Let's go and drill every bone, because if that's the breeding season, we might find 7 or 8 females, and then the others are pretty much by default males if we know it's the middle of the breeding season, because all the females have medullary bone.

Now, let's analyze those 2 datasets. Maybe we'll see a difference, and maybe we won't.

Lex Fridman

I love how that frustration is a catalyst for figuring it out. You're searching for a place, a piece of evidence that just shows you clearly.

Dave Hone

There are ways in.

Lex Fridman

Yeah, there's a way in.

Dave Hone

This is the thing.

Lex Fridman

There's always a way in.

Dave Hone

Yeah, there are ways in. And maybe we've got to get lucky because maybe it's not the breeding season. Or maybe that was just a group of all males, and therefore we're not going to get the signal we're looking for.

But there's enough of them, and they're common enough, and yet, still digging in Mongolia, we keep finding new species. We keep finding new, cooler stuff. But I'm like, “Can we dig up some more Protoceratops?”

Because, actually, however cool these new things are, genuinely, if you want to know what dinosaurs are and how they worked, another 100 Protoceratops will probably tell us a lot more than 50 new species, however cool 50 new species might be.

Lex Fridman

Paleontology is an incredible discipline. It really is Sherlock Holmes territory. This was an incredible conversation. I'm really grateful for all the work you write and put out there.

Dave Hone

Thank you.

Lex Fridman

The podcast is incredible. Thank you for being you, and thank you for talking today.

Dave Hone

Well, thank you very much for having me. I hope I haven't worn out my welcome with dinosaur—

Lex Fridman

No.

Dave Hone

—stories.

Lex Fridman

Oh, we could talk for many more hours. Thank you, brother. Thank you, Dave.

Dave Hone

Thank you.

Dave Hone: T-Rex, Dinosaurs, Extinction, Evolution, and Jurassic Park | Lex Fridman Podcast #480 | BidClub