Pod Insights Daniel and Kelly's Extraordinary Universe Was the Tyrannosaurus rex fast or slow? (Featuring Dr. John Hutchinson) About this episode Daniel and Kelly talk to Dr. John Hutchinson about how large animals move.
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Transcript 10,614 words · 8 speakers
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2:18 Kelly Weinersmith? When I was a kid, I was absolutely obsessed with Jurassic Park. It wasn't just because of the dreamy Ian Malcolm, but mostly was because I desperately wanted to be a paleontologist. The idea of bringing long extinct animals back to life through the magic of biology was absolutely enthralling to me. And I went to the cheap theater to watch Jurassic Park on the big screen as often as my mom was willing to take me. The scene where the T Rex is chasing the Jeep, carrying the injured Ian Malcolm to safety, is burned into my memory. But even as a kid, I remember watching that scene and wondering to myself, could an animal that big really go that fast?
3:00 Kelly Weinersmith? If so, why is the huge Brontosaurus not similarly swift? This is a difficult question to answer. After all, how do you even go about figuring out how an extinct animal moved? They're not around to be videotaped anymore, and the muscles that hold keys to answering questions like these have long since decayed away. Well, on today's show, we're talking to Dr. John Hutchinson, who studies the movement of long dead animals, while answering amazing questions like, can hippos get airborne? And how do elephants run? This is the perfect topic for Daniel and Kelly's Extraordinary Universe, because it's the happy intersection of biology and physics.
3:42 Kelly Weinersmith? Welcome to Daniel and Kelly's extraordinarily fast-moving universe.
4:00 Daniel Whiteson? Hi, I'm Daniel. I'm a particle physicist, and I've always considered myself a large animal.
4:04 Kelly Weinersmith? Hi, I'm Kelly Weiner-Smith. I'm a biologist, and I sort of fluctuate between being a large and a larger animal. It depends on how close we are to the holidays. But I always feel great about myself, so it's all good.
4:19 Daniel Whiteson? And so, Kelly, what do you think is your top land speed?
4:26 Daniel Whiteson? Or what could Kelly outrun? Let's put it that way.
4:29 Kelly Weinersmith? Hmm, I've definitely outrun some turtles on the property.
4:32 Daniel Whiteson? Okay, that's good. Let's start there.
4:34 Kelly Weinersmith? There are some fast frogs on the property, so maybe somewhere in between those things.
4:41 Daniel Whiteson? Wow. Are you telling me a swarm of frogs could take you down?
4:45 Kelly Weinersmith? Oh, I mean, they could catch up to me, but they're pretty tiny. You know, I think I could give them a couple of good swift kicks. I have taken some taekwondo, so maybe I can give them a couple of chops.
4:56 Daniel Whiteson? All right. So all frog listeners, be warned, Kelly can defend herself.
4:59 Kelly Weinersmith? Yeah.
5:00 Daniel Whiteson? I'm not a very fast person. I could not outrun a cat or a dog or even a rat. I've chased a rat around our garage and lost that race. Rat's surprisingly fast.
5:10 Kelly Weinersmith? Yeah.
5:11 Daniel Whiteson? But to my credit, I do have offspring that are surprisingly fast. My son is a runner, and he runs a mile in shockingly four minutes and 20 seconds or something. And so I think I want to take some credit for that, even though it's probably more likely to be cosmic ray mutation or the transcription errors or something that led to that.
5:29 Kelly Weinersmith? You're one of those parents whose children's accomplishments are your accomplishments.
5:34 Daniel Whiteson? Absolutely. Why else have kids? I put his times on my CV for sure.
5:41 Kelly Weinersmith? Does that help with funding? I can't imagine it would.
5:44 Daniel Whiteson? It doesn't. It doesn't. No, it's wonderful to see your kids grow up and just have different skills and interests than you do. It's fantastic and also surprising sometimes.
5:54 Kelly Weinersmith? Yes. No, my son has amazing abs. Like, you could put him in any position and he can sort of lift himself up with his core. And it's crazy. And my daughter's starting her first math competition. Both of those things are just, my kids are amazing and I had something to do with it, but I don't know how much credit I get for either of those things.
6:12 Daniel Whiteson? Turns out biology is complicated, right? Who could tell?
6:16 Kelly Weinersmith? Yep. Yep. It's true. And you know, another thing that's complicated is how do you portray biology in movies and TV shows, especially when you're really pushing the boundaries of the biology? And we have a really great question about that today from a listener. Let's go ahead and hear it.
6:33 Speaker 04 Hi there, Daniel and Kelly. It's Ben from Melbourne in Australia here. And I've got a question about large creatures, including giant people, and how they move. So I've noticed in a lot of movies and TV shows when something giant is depicted, like Giant Ant-Man in the Marvel movies, they're often depicted as moving really slow, kind of like in slow motion. But then in other media, we've got giant things like the Ava units in the Evangelion anime, which move really, really fast. And it got me wondering, is there any physics reason or any biology reason
7:14 Speaker 04 why one of those depictions is accurate as opposed to the other? Or does it depend on the particular case? Really enjoy the podcast and really looking forward to what you might have to say.
7:27 Kelly Weinersmith? So this is an amazing question, and I was so excited when we got this question because I had somewhat recently met a professor who studies very large animals. And we were in a meeting with a bunch of other people and there were things going on. And I didn't get a chance to ask him all the questions that I wanted to ask him about his research. So I was so excited to have an excuse to invite him on the show. And so today, we have Dr. John Hutchinson on the show to tell us all about how very large animals move.
7:53 Daniel Whiteson? And what a giraffe burger tastes like.
8:01 Kelly Weinersmith? Dr. John Hutchinson is a professor of evolutionary biomechanics and a fellow of the Royal Society. His research straddles the fields of evolutionary biology and biomechanics with an emphasis on how very large animals stand and move, and how locomotion evolved in different groups of land vertebrates. Welcome to the show, John.
8:19 Speaker 05 Thank you very much, Kelly.
8:21 Daniel Whiteson? Kelly, in your introduction, you neglected to mention that John also has an incredible array of heads on the wall behind him.
8:29 Kelly Weinersmith? Well, I didn't know that when I wrote the intro.
8:31 Daniel Whiteson? What's going on there?
8:32 Speaker 05 Yeah, it's my mask collection.
8:34 Kelly Weinersmith? Oh, cool.
8:35 Speaker 05 Which got particularly ironic early in the COVID pandemic, but it only encouraged my collection of masks.
8:42 Daniel Whiteson? So for those of you just listening, we see an octopus and what else is going on? A giraffe?
8:49 Kelly Weinersmith? Thulu, giraffe, are these all from places that you've visited?
8:51 Speaker 05 Just random places, often just gifts from people or I find them like at a...
8:58 Speaker 05 Arts sale kind of thing, or whatever.
9:01 Daniel Whiteson? I don't know why you don't just wear them when you jump onto a Zoom call. That'd be very dramatic.
9:07 Speaker 05 Yeah, some of them would fit.
9:09 Kelly Weinersmith? All right, well, let's pull back and talk about what got you interested in studying the movement of very large animals.
9:16 Speaker 05 It really goes back, I think, to being a high school student in a physics class. And I remember my teacher had like a bulletin board with some news articles or something on it. That's the way I remember it. And one of them explained why King Kong and Godzilla were physical impossibilities because they were just too big to support their own weight. And I was a big, big monster movie fan, just way too early for my years, really into kaiju type movies. And that was really interesting to me because it made me grapple with my
9:55 Speaker 05 growing interest in science and my longstanding interest in the arts and fiction. So I had to think about, oh, wow, that actually really makes sense, but too bad.
10:08 Kelly Weinersmith? And you were like, one day I'm gonna crush dreams, just like the author of that article.
10:15 Daniel Whiteson? Walk us through the argument. Why does physics say that biology can't get too big?
10:19 Speaker 05 The simplest explanation is what they call the square cube law, or well, there's various terms for it. But as animals get bigger, their wet mass or their weight goes up by a linear dimension cubed. So you have a length, a width, and a height. That's your mass, your volume, so forth. So that increases with your size overall. Mass is a metric of size, more or less. But as your mass increases, your area, your linear dimension squared, so cross sectional area, only goes up proportionately by the linear dimension squared. So very
10:59 Speaker 05 quickly, the amount of weight you support on a given area gets higher and higher and higher unless you do something to change your mechanics.
11:11 Speaker 05 Of movement.
11:12 Daniel Whiteson? So let me interpret that. Assume, for example, we have a spherical Godzilla, right? Because I always like to assume spherical monsters.
11:19 Speaker 05 Yes.
11:20 Daniel Whiteson? Then you're saying the volume of that sphere goes with the radius cubed, right? It's like 4/3rd of pi r cubed.
11:27 Speaker 05 Yep.
11:27 Daniel Whiteson? But the surface area of the sphere is 4 pi r squared. And so when you double the radius, the volume goes up by 8, but the surface area only goes up by 4. And as that continues, as the radius goes up and up and up, you get to actual Godzilla sizes, the ratio gets larger and larger, of volume to surface area. But why is that a problem? Like, why is it a big issue to have a lot of wet mass inside your surface area?
11:52 Speaker 05 Because of biology. Because animals are made of the same stuff that has intrinsically the same mechanical properties, the same strength, fundamentally. That's the most important thing. See, the amount of force per unit area a bone or a muscle can support is fairly constant across vertebrates that move on land in particular. Because this is all operating under gravity is the assumption. If, once animals get in the water, all bets are off. It's effectively zero gravity, more or less. So then this square cube law is not such a concern. On land, the strength of tissue becomes fundamental.
12:33 Kelly Weinersmith? Is the limiting factor there mostly bone, or mostly muscle, or it has to be both? What limits what an animal can hold?
12:41 Speaker 05 I think this is still a big question in science. That you would think it might be bone, because bones are there to support body weight against gravity. But bones form joints that muscles act around to support animals. So there is the living component, the contractile component of support, which is muscle. But then there's all the other passive stuff, bone, ligaments, and cartilage and so forth, that also provide support. And what we don't really understand yet is how much of a role each of those things plays, and how that balance changes as animals get bigger. One thing we do know is that As animals get bigger, land animals, I should specify land vertebrates.
13:25 Speaker 05 As they get bigger, they tend to straighten their legs. So that shifts their mechanics of support to using their legs more and more and more like pillars, which transmits more of the force down the long axis of the bone. So like when we stand, we're using our legs like pillars, more or less. We're quite unusual actually for animals of our size in the way we do that. It's very efficient, providing a lot of passive support. So mostly the bones are providing a lot of support. Once you get to a very, very pillar-like posture. Whereas intermediate postures with more bending of the limbs would involve presumably more muscle activity.
14:04 Speaker 05 But you know, this is hard to figure out because there are so many components acting around each joint in any real organism. It's a really difficult mathematical problem.
14:14 Daniel Whiteson? So my takeaway is that it's not necessarily impossible to have any given size of animal, but that the task of the animal, the sort of biological engineering needed changes as the animal gets bigger or smaller because of these different ratios. And the strategies that we have are vertebrates on earth might not scale to like really big Godzilla's. But does that mean, for example, you couldn't have a fundamentally different biology? You know, some crazy hollow thing or a different kind of biological engineering or no joints? Or I don't know, something, you know, really out of this world that could allow for much, much larger animals?
14:49 Speaker 05 That is a great question, like in terms of like other worlds or such. Certainly, we don't know what tissue could achieve. We only know it's there.
14:57 Kelly Weinersmith? So Daniel was asking, are there different ways to get bigger? Like, can you hollow out your insides or something? You mentioned in water, it's effectively zero gravity. Does that mean that blue whales, like we could have something a hundred times bigger than that? Or does something else limit size in the ocean?
15:16 Speaker 05 This is another big question we don't understand. We don't understand what the upper limit of size is on land or in water or anything. We only know what we see. And the largest animal ever so far is the blue whale. There are some fossils that kind of seem to maybe come close to that in size, but blue whales are the biggest. But it doesn't mean that animals can't get any bigger than that. It's just that that's what evolution has produced. And certainly, there are other mitigating factors like physiology, cardiovascular issues, breathing, ecology. So food is a huge constraint on body size. If you don't have enough food around, if you're in an unstable environment where food resources
15:59 Speaker 05 are crashing all the time, like in the face of environmental change, then being big is a very terrible biological strategy, so to speak. So, uh, large body sizes has many limits, not only the, only the physical. There is a whole different body plan out there that we can look to in nature to ask questions about mechanics of size and support, and that's, uh, arthropods. What's really interesting is that even in the most extreme cases in the fossil record, we see no gigantic arthropods.
16:34 Daniel Whiteson? Remind me, what's an arthropod?
16:36 Speaker 05 Animals with exoskeletons, so insects, crabs, crustaceans, spiders, so forth. Things with their skeleton on their outside.
16:43 Daniel Whiteson? So no lobsters the size of blue whales so far?
16:46 Speaker 05 Yeah, yeah. But so they keep their muscles on the inside, which constrains how big their muscles can be, because they've got to have not only all their muscle on the inside, but all the other stuff, their circulatory system, so on and so forth. So that constrains them to a certain degree, but also other factors like their circulatory system constrain their size. So they are weirdos. But also, arthropods are weirdos because their muscles break all the rules of what muscles can do. I talked about vertebrate muscle having pretty much the same properties across any size of vertebrate, but insect muscles have tremendous variation in what kind of properties they can have. But they
17:28 Speaker 05 still could not enable like a 50-ton ant.
17:32 Kelly Weinersmith? Oh, there was a movie when I was a kid that had a giant ant after a nuclear war. And yeah, them. Oh, oh, you've crushed my dreams. I was really hoping that that would be a silver lining.
17:44 Speaker 05 I think I specifically chose that to crush your dreams.
17:47 Kelly Weinersmith? Oh, man. Well, good job. Good job. Spot on.
17:50 Daniel Whiteson? A little taste of your own medicine there, Kelly.
17:52 Kelly Weinersmith? Oh, ouch. Could you tell us a little bit more about the different kinds of insect muscles? How do they break the rules? Or arthropod muscles?
18:00 Speaker 05 Okay, this is getting outside of my expertise a bit, but they have really different sizes and proportions of proteins that make up muscle. There are three major proteins that make up muscle, actin, myosin, and titan. And those three molecules interact to produce these sliding filaments that lengthen and shorten the muscle unit called the sarcomere. Invertebrates, they're all kind of made the same. But in insects, they're built in different ways. They can contract at different rates. They can do all kinds of crazy stuff. And I can't explain that to you. I'm not an insect muscle physiologist. I have huge respect for them because they study things that are really weird to me.
18:42 Daniel Whiteson? Can I admit something that may be embarrassing?
18:44 Kelly Weinersmith? Yeah.
18:45 Daniel Whiteson? I didn't know until this conversation that insects had muscles. My mental image was that they just basically had some sort of hydraulic goo inside their exoskeletons, and I had no idea how they moved. So that's fascinating. Are you saying it's like differentiated inside there? Like if I cut into a 50 ton ant, it's not just like a fire hose of goo that's going to spray out?
19:06 Speaker 05 No, no, no, they have plenty of internal structure. Spiders do move using a largely hydraulic limb structure. So they have muscles, but they're mostly powering their leg movements through a hydraulic movement that's coupled to their circulatory system. So they're pumping fluid around their bodies and using that fluid to move their legs.
19:27 Daniel Whiteson? So are muscles conserved across all animals? Like everything that's mobile on Earth uses some kind of muscle?
19:34 Speaker 05 Yeah, every animal. There are other things that do weird stuff. I guess once you get down to a single cell, it becomes a question of what really is a muscle? It becomes a little weird. I mean, you're using proteins to spin a flagella, a little whip-like structure in bacteria and other small, small organisms. So. I think if we're talking about muscle in the way we're familiar with it, with the three major components, Actin, Myosin, and Titan, then that's an animal thing, more or less.
20:04 Daniel Whiteson? And so on that topic, why don't we have like macroscopic sized bacteria? Why don't we see the ocean filled with like blue whales and then like bacteria the size of a blue whale with a massive flagella behind it?
20:15 Speaker 05 Oh, boy.
20:16 Daniel Whiteson? And how come nobody's made that monster movie yet? That's the real question.
20:19 Speaker 05 Yeah, well, I mean, the blob was kind of in that direction.
20:26 Kelly Weinersmith? I loved that, too.
20:27 Speaker 05 I don't know how you classify the blob, although if you know your H.P. Lovecraft lore, it was probably a shoggoth. Um, anyway, yeah, bacteria. Hmm, I don't know if I could give you an easy answer there. I think diffusion would be a big problem for them. They've got this big, tough cell wall and they're one cell that relies on stuff to get in and out of that cell wall and move around the organism. They have no respiratory, circulatory systems, anything like that. They just rely purely on diffusion. So I think that's going to be a big constraint on any single celled organism is diffusion. And maybe the support of their cell wall itself might just crumple under its own weight. And they can't really move.
21:12 Speaker 05 I mean, it would take a huge flagellum to move a big bacterium through the water. I can't even imagine how the mechanics of that would work.
21:21 Daniel Whiteson? I'm sure you can imagine it.
21:24 Daniel Whiteson? Mr. Monster Movie over there for sure has the mental image.
21:27 Speaker 05 Give me a few million in VFX budget and I can imagine it, yeah.
21:32 Daniel Whiteson? Done and done, yes.
21:34 Kelly Weinersmith? Oh, yeah, because we've got loads of money.
21:37 Speaker 05 James Cameron.
21:37 Kelly Weinersmith? There you go.
21:38 Daniel Whiteson? Welcome to Daniel and Kelly's production studio.
21:41 Kelly Weinersmith? There you go. So the conversation we've been having has gone between physics and biology a lot. So you clearly know a lot about both. And so after the break, I'm going to ask you to explain why biology is better than physics.
21:55 Speaker 05 Oh, dear. All right.
21:57 Daniel Whiteson? If possible.
21:57 Speaker 05 The gauntlet has been thrown down.
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23:06 Kelly Weinersmith? Hi, I'm Jenna Ushkowitz. You might know me from Glee. This is At the Table, the food allergy podcast, a show about food, connection, and what it really looks like to live with food allergies. Each episode, we hear stories from real people like Daniel. People would always think I was lactose intolerant, so I just kind of shortened my explanation to I'm deathly allergic in a big way that defined a lot of my childhood. And while there are challenges, there are moments that remind you you're not alone. One of the best guys that I dated, he made a point to memorize all my food allergies. So join us and hear their stories and more because living with food allergies isn't just about what you can't eat. It's about still having your seat at the table.
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24:11 Kelly Weinersmith? And we're back. All right, so John, you know a bunch about physics, a bunch about biology. Do you have a favorite? Or what do you love about the intersection of these fields?
24:20 Speaker 05 I do love the intersection. I love intersections of fields in general. I like to defy boundaries. I like to think about how a lot of boundaries we erect with our minds are false, and they're just there as conveniences. So however, in physics is physics, it's very easily circumscribable, much like mathematics is, whereas biology is fuzzier. I like that aspect of biology, maybe because I like fuzziness. Although physics can get pretty fuzzy, I guess down at the weird end of scales, maybe Daniel, you can agree that or not.
24:56 Kelly Weinersmith? That's where Daniel lives. Yeah, at the weird end.
24:58 Daniel Whiteson? I'm at the weird end of everything.
25:01 Kelly Weinersmith? That's right.
25:02 Daniel Whiteson? But you ended up a biologist. I mean, by name, you're in the evolutionary biomechanics department. You're not like in a physics department doing biophysics. And I completely agree with you that these are artificial dotted lines that we draw on a smooth spectrum of natural curiosity. But I am curious why you ended up on one side of that than the other. Like, why are biologists more likely to hire you than physicists?
25:25 Speaker 05 Oh, my training very much is in biology into my PhD. I am a biologist fundamentally. I can't claim to be a physicist. It's just not my training. I'm not an engineer or anything like that. I did do a postdoc in an engineering laboratory, which gave me a bit of street cred with that crowd and did teach me a lot about that kind of perspective with Newtonian mechanics. But yeah, I couldn't go work at a physics department. They could tell that I was an imposter.
25:54 Daniel Whiteson? No, you'd just be like, hey, what happens if we have a really high-energy collisions of very large animals? Two elephants running at each other at high speeds? Let's do that experiment, right? It's easy to be in the physics department.
26:08 Kelly Weinersmith? Well, can we get into the details of your day-to-day life studying this stuff? So like, when I think about studying movement in small mammals, I can imagine, for example, putting them in a CT scanner or an X-ray machine. But you study animals that are just absolutely massive. And so presumably, they don't stay still in those machines, or there's no machines big enough. So how do you get your data?
26:29 Speaker 05 Well, I'm interested in the size spectrum of animals in general, because I don't think you can understand big animals without also understanding smaller ones. It's just that we do have a lot of knowledge of how smaller animals work. And just up until my work, there hadn't been that much research on how the biggest land animals worked. So I do work on living animals using like X-ray machines. We have multiple X-ray video cameras, as you can loosely call them, where you can have an animal moving through two planar X-ray systems with high-speed video cameras attached to them and use those in animation software to reconstruct how the skeleton moved in the living animal. That's really cutting-edge stuff in our field that allows us to see inside the animal and see its skeleton moving in life.
27:14 Speaker 05 It's been a big game changer over the last 20 years. But yeah, we can't do that with big animals. The biggest size you can image is about soccer or football-sized, for Americans, soccer ball-sized roughly. And the technology, for reasons I don't understand, or maybe just demand, has not created any machine that can do a volume bigger than that. So doing even small parts of big animals is impossible with that kind of stuff. We do more conventional kinds of study of larger animals with motion capture or just high-speed video or whatever. We use other devices to measure how hard they exert force against their environment, so what we call force platforms, and pressure pads that measure the force per unit area
27:59 Speaker 05 they apply to the ground. We have lots of cool toys to measure what we would call the kinetics, so the forces and related things, and the kinematics, the motions of organisms.
28:11 Daniel Whiteson? I'm confused when you say that you can only image something the size of a soccer ball, because like you can put a whole human inside a CT machine, and there are some pretty big humans out there. Why can't we do that with animals also?
28:23 Speaker 05 You can't have them moving around with like a video camera going on, capturing data. The, in a CT scan, you have to have an individual remaining still, because you're taking serial slices, serial X-rays of the individual to then piece together the whole 3D person. So if they move, actually, your image gets screwed up.
28:42 Daniel Whiteson? I see. You can't convince an elephant to stay still.
28:45 Speaker 05 Yeah, yeah.
28:46 Kelly Weinersmith? What's the biggest animal that you've studied?
28:48 Speaker 05 I've worked a bit on the big sauropod dinosaurs. I'm not so well known for doing that, but I have published a bit on them with some colleagues. I'm more well known for studying the big carnivorous dinosaurs like T. rex. I really made my name with an early study I did showing that T. rex couldn't run quickly. Again, smashing dreams, making some paleontology fans rather upset, but it was well received scientifically, so I'm very pleased about that. I've worked with elephants a lot, about as much as I've worked on T. rex and its kin. I've worked on living elephants from zoos around the US and the UK to more wild type elephants in Thailand, working with elephants that were either previously used in logging
29:31 Speaker 05 or tourism or even used in racing. So I got to measure how the fastest elephants could move, which was really, really cool.
29:39 Daniel Whiteson? How fast can an elephant move?
29:41 Speaker 05 They can go up to almost 15 miles an hour, which might not sound that fast, but that's a challenge for me to keep up with that pace.
29:52 Speaker 05 Still pretty impressive to see like a 4,000 kilogram animal traveling at 15 miles an hour.
29:58 Daniel Whiteson? That's a lot of kinetic energy.
30:00 Kelly Weinersmith? I bet it feels really fast if it's chasing you.
30:02 Speaker 05 Oh, yeah. What we found with that work was that even though elephants don't go airborne at any time when they go quickly, which is kind of what we thought, they do sometimes only have support on one limb while the other three limbs are airborne, kind of doing the splits in midair. So that was really cool to see how extreme the gait of elephants could be. They really do move in rather extreme ways, even though they don't go fully airborne.
30:31 Daniel Whiteson? That's fascinating. You talk about the gait of elephants, like whether they're ever have all four legs off the ground? What animals do ever have all four legs off the ground?
30:39 Speaker 05 Pretty much everything, except like tortoises and other really slow animals. And just this past summer, we showed with another paper that when hippos go really quickly, they leave the ground with all four feet, which elephants don't. So that was a nice thing to find. Which had never been reported scientifically. We know that rhinos, which get very, very big, up to 3,000 kilograms or so, so rivaling the size of some like Asian elephants. They can gallop, they can leave the ground with all four feet. So they are kind of in that zone of being big and being athletic. That is apparently hard to achieve.
31:17 Daniel Whiteson? You discovered flying rhinoceruses? That's amazing.
31:20 Speaker 05 The rhino thing was known, but the flying hippo thing, that was a small new contribution that I'm still proud of. It got a lot of news attention. I was really kind of pleasantly surprised by that.
31:31 Daniel Whiteson? I want to come back to dinosaurs in a minute, but first I have a question about elephants, because I've always heard this story about elephants, that the reason elephants have really big ears is because of this volume surface area question. And, you know, you've scaled up the elephants to be so big, it's got so much meat, it's hard for it to stay cool. And so having really big flappy ears is like a cheap way to increase your surface area without increasing your volume. Is that pop science nonsense, or is that real science?
31:57 Speaker 05 There is some truth to that. So there's big differences in ear size in Asian versus African bush elephants. The bush elephants in Africa have much bigger ears. That corresponds to being out there in hotter temperatures in the open, exposed to sunlight and so forth. I think it's pretty well accepted that that difference in ear size and just the overall large ear size in elephants overall, relates to them using the ears as a cooling mechanism. And they do wave their ears, so they get convective cooling, moving the air quickly past to ensure that there's always more air to unload the heat onto as they keep airflow going.
32:38 Kelly Weinersmith? And mammoths had little ears, right?
32:40 Speaker 05 Some woolly mammoths did. So, you know, there are quite a few different species of mammoths. The woolly mammoth is the one we know best from animals preserved in frost in Siberia. Those had a lot of body parts reduced to avoid frostbite, probably.
32:54 Daniel Whiteson? You know, I noticed that in Far Side. Far Side, the mammoths always have kind of little cute ears. And I remember as a kid being like, is that right? So it's amazing Gary Larson, ahead of his time.
33:04 Speaker 05 Oh, he knew his science. Yeah, he paid attention.
33:08 Kelly Weinersmith? Can I dig in a little bit more to your elephant study before we go to dinosaurs? So how did you figure out that the elephants had one foot on the ground at all time? Was it just a really good camera? And how do you make an elephant run on command? That sounds scary.
33:21 Speaker 05 It was just using pretty conventional cameras or not very high-speed cameras. We did eventually get hold of some good cameras that helped confirm it even better. But when I was just a postdoc or even a grad student, yeah, I was just like in my mid twenties. I started working on elephants, trying to answer the question, well, do they leave the ground with all four feet or not? We didn't think so, but I wanted to test that empirically. And so I just took a video camera out to some zoos, couldn't get them going quickly, and then got in touch with a guy in Thailand. He was interested in this kind of question. And I went out there with just a conventional video camera and he knew all of the elephant keepers and just got them together and made it into kind of a game for them or a contest.
34:04 Speaker 05 So each elephant has its own companion, a mahut or a rider, who pretty much grows up with the elephant and they have a very strong bond in Thailand. And so the mahut would encourage the elephant by whatever means he thought was reasonable, like calling to it usually, or having someone run in front of it, or have it go toward a friendly elephant. And that would motivate it to go quickly.
34:30 Kelly Weinersmith? Cool.
34:30 Speaker 05 It certainly did work in Thailand. We got much faster elephants than we ever did elsewhere.
34:36 Kelly Weinersmith? I love the idea of explaining to your thesis advisor. I couldn't answer the question. I couldn't get the elephants to go fast enough. Like, that's a very unique problem.
34:44 Speaker 05 This is animal research. Yeah, motivating animals, very challenging.
34:48 Kelly Weinersmith? I, it's true.
34:49 Daniel Whiteson? Do you have to get an IRB there? Like, do elephants get grumpy if you make them run? Or can you possibly hurt them or something?
34:56 Speaker 05 Yeah, there's always stringent ethical approval involved because even just stress is a concern. So you have to explain how are you going to mitigate stress? What are you going to do if an animal seems stressed? Well, you terminate the experiment. What does stress look like? Those are important questions. And avoiding fatigue also is really important. So you give animals lots of rest because we don't want to study fatigue. We want animals that are fresh.
35:20 Kelly Weinersmith? Let's go back to dinosaurs. You mentioned T. rex right after we had finished talking about methods for looking at animal movement. But when you're studying dinosaurs, of course, you can't see them move at all. So how do you study animal movement in long-dead animals?
35:34 Speaker 05 So we have. Kind of two things. We have the fundamental principles of animal movement that we know from living animals, which tell us some pretty good, reliable, general rules that we can use as expectations to apply to extinct animals, or at least give boundaries for here's what this could be like, here's how big the muscles might be relative to the limbs, that kind of thing. And then we have physics. So we can, and this is what I did in my PhD thesis, we can build either a very simple or a very complicated mechanical model of a dinosaur for its own sake. So we actually tried to reconstruct, like in a computer, usually,
36:16 Speaker 05 what the animal looked like, its dimensions, and give those dimensions, physical properties, mass, center of mass, inertia, so forth, stuff that physicists would care about. And then ask questions of that model, basically, what can you do? What is possible with this representation of a dinosaur? And then you can test hypotheses like, well, given this set of assumptions about a T-Rex, could it run quickly or not? How much muscle mass would it have needed to run quickly? And is that reasonable, given how much we could fit on the skeleton or not? And I tested that and found that no, it couldn't run very quickly, not like a racehorse, like 25 miles an hour, but still possible to do more like
37:00 Speaker 05 kind of elephant speeds, maybe 15 miles an hour, which for an animal that could get bigger than an elephant, it's still pretty darn good.
37:07 Daniel Whiteson? So what you're doing here is sort of like imagining how you might build a dinosaur, saying like, well, how do reptiles move and how do current animals move? And you know, the sort of shape of a dinosaur. So you're sort of imagining a biological model of a dinosaur and then studying that?
37:21 Speaker 05 It's setting up a set of constraints. So here's what's possible, given what we know from living animals, the range of variation we see in living animals, which sometimes can be pretty conservative. And using that as inspiration to make assumptions about extinct animals. So we have the bones, that's direct information. Sometimes we have fossil footprints that we can use to kind of give an idea, okay, this animal stood on two feet with the feet very close together, not sprawled out to either side. And yeah, so ultimately then we can, for example, reconstruct muscles attaching from bone to bone.
38:00 Speaker 05 To guide their lines of action and that can be done by looking at living animals and seeing, okay, where are the muscles of living animals attach? And I did a lot of that in my PhD work and found that if you look at living animals, especially the closest relatives to dinosaurs, like living birds and crocodiles and other reptiles, the leg muscles are really conservative. So you can pretty well predict where the muscles attach from the shape of the bones, from marks on the bones, which reveal the actual interface between the muscle or tendon and the bone itself.
38:37 Daniel Whiteson? When you say conservative, you mean similar across species?
38:41 Speaker 05 Yeah.
38:41 Daniel Whiteson? Not like in small government?
38:43 Speaker 05 Yes, yeah, similar across species. So yeah, consistent and probably predictable that we can make assumptions about the anatomy of extinct animals that are reasonable. They're not going to be perfect, but they're pretty well grounded in actual evidence. And we can be very explicit. Well, I think it was this way because of these data that we have from living animals and this information that we have directly from the skeleton.
39:08 Daniel Whiteson? The physicist in me likes that you're like building a model and exploring, you know, the speed and motion of that model, but then also wonders like, what do we know about how that model might differ from real dinosaurs, right? You are making assumptions and extrapolations. Then along with that, you might develop like some uncertainty window or some band of your knowledge and confidence to say like, well, we're pretty sure. Or is that something you can quantify? Or is the information so sketchy that we can just sort of like make qualitative arguments about how well we know this stuff?
39:38 Speaker 05 It is difficult to make very specific predictions. And any quantitative arguments are always in some very rough bounds of possibilities. So like trying to predict the speed of an extinct dinosaur, we don't even know for sure what the bounds can be, but we can do what we call sensitivity analysis. So the different inputs we put into the model. So how big are the leg muscles? Where are they attached to, so on and so forth? And then see what the output of the modeling analysis is. So how does that change running speed if we change these assumptions in the model? Another thing we do that's really important, and this is where my training in biology really comes to bear in my work with living animals, is we can apply the same methods
40:21 Speaker 05 to a model of living animals and see, can we predict how a living animal works based on the same kind of modeling approach as we apply to an extinct animal? And comfortingly, when we do those kinds of tests, they usually do pretty darn well. So we can predict that a bird can run bipedally, whereas a crocodile that doesn't run bipedally cannot.
40:44 Daniel Whiteson? That's very cool that you apply your mechanism to animals where you can check yourself. That's very cool.
40:48 Speaker 05 Very important.
40:49 Daniel Whiteson? But also, as a complete non-expert in biology or in dinosaurs, I have the sense that our mental imagery of how dinosaurs stood and moved and looked has changed over the last fifty or hundred years. You know, like T. rex used to look more like standing up, and now we think dinosaurs might have all had feathers or something. Doesn't that tell us that a lot of what we're assuming, that the assumptions we're making, might be changing with time and might have uncertainties we haven't accounted for?
41:16 Speaker 05 Yeah, and I think that's the great thing about science is these things can always be updated. Everything's provisional. They need to be revisited. I mean, someone might come along and show that my work that I did twenty years ago is wrong, and that's just the way it goes. The key thing I think is to be explicit, to say, here's my set of assumptions. Here are the data that go in. Here are the data that go out. Here's the methods that are used. So it's all reproducible, and someone can go back and say, oh, no, I found some other information that changes the inputs completely, or changes the way we should even model the whole thing completely, the way the whole system might work. And so they can repeat or do a completely new invention of that kind of analysis. I think that's the key.
41:59 Daniel Whiteson? And sorry if I missed this earlier, but what was the thing that limits T. rexes to not going much faster? Or what was the thing that we learned about T. rexes that changed people's minds about why they couldn't go quickly?
42:10 Speaker 05 Living land animals, no matter what their size is, can only devote so much of their body mass to muscle that supports the body weight. You have to have not only muscles, but bones, skeletons, lungs, brains, so on and so forth.
42:28 Speaker 05 And the upper limit of that muscle mass that we can see in nature appears to be ostriches. Large fraction of ostriches is leg muscle that supports them. You think about an ostrich, it's got a long, skinny neck, tiny little head, tiny little wings, no tail to speak of, a big torso, but really, most of it is these big, long, meaty legs. And no dinosaur was really built like that. Nothing like a T. rex was built to have a body devoted to muscle like an ostrich does today. So we could use an ostrich as like an upper limit for what we know of in terms of how much muscle a dinosaur might have had. And even that, that would be a bit straining credulity if we did say a dinosaur had that much muscle.
43:13 Daniel Whiteson? Are you saying an ostrich would beat any dinosaur in a footrace?
43:18 Speaker 05 Yeah, yeah, I think it probably would. But even ostriches have more muscle devoted to their limbs than like fast animals like cheetahs or big animals like rhinos or elephants do. They're super muscular animals.
43:30 Kelly Weinersmith? All right, so let's take a break. And when we get back, we're going to hear about some weird stuff that's been in John's freezer.
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44:43 Speaker 06 Hi, I'm Jenna Oshkowitz. You might know me from Glee. This is At the Table, the food allergy podcast, a show about food, connection, and what it really looks like to live with food allergies. Each episode, we hear stories from real people like Daniel. People would always think I was lactose intolerant, so I just kind of shortened my explanation to I'm deathly allergic in a big way that defined a lot of my childhood. And while there are challenges, there are moments that remind you you're not alone.
45:13 Daniel Whiteson? One of the best guys that I dated, he made a point to memorize all my food allergies. So join us and hear their stories and more because living with food allergies isn't just about what you can't eat, it's about still having your seat at the table. Brought to you by Genentech and Novartis. Listen to At the Table, the food allergy podcast on America's number one podcast network, iHeart. Follow At the Table and start listening on the free iHeartRadio app today.
45:48 Daniel Whiteson? As someone who is married to a biologist and has weird stuff in his freezer as a result, I am terrified to learn what John might have in his freezer.
45:58 Kelly Weinersmith? Yeah, so John, you have a really great blog called What's in John's Freezer? And I decided I shouldn't look at it with my husband around because it might turn his stomach too much. But you've had some cool stuff in your freezers. Can you tell us about some of the cool stuff that's in your freezer and what you've done with it?
46:14 Speaker 05 The glory days are gone. I used to have cooler stuff. Although, I mean, there's still some cool stuff there. I've been trying to get rid of stuff lately because it just got too full and became kind of a hazard with piles of frozen stuff getting up to the ceiling of this walk-in freezer. But yeah, I mean, over the years, I've had a lot of parts of elephants because elephants die in captivity and zoos give parts of them at least to me to study for research. And then we take those parts. And use them to help us understand like the anatomy of elephants and how things can go wrong in elephant feet, which are a big cause of mortality in elephants. They have a lot of problems with their feet. We can use the information from cadavers to actually
46:55 Speaker 05 contribute to taking care of animals like elephants. A lot of elephant parts, rhinos, never had a hippo, lots of giraffes, lots of crocodiles of all kinds of different species. I love crocodiles. I'm crazy about them and have done a lot of research on crocodiles.
47:13 Daniel Whiteson? What's to love about crocodiles? Sorry, I gotta ask.
47:15 Speaker 05 Oh, they're so, they're so bizarre.
47:20 Daniel Whiteson? I'm just shocked, two biologists, everybody out there should have seen their faces, the horror, the outrage, the surprise. Really, tell me, I'm imagining crocodiles like eating dogs and like snatching babies. What's amazing about crocodiles? Why do we love them?
47:33 Speaker 05 Well, just that, I mean, that's pretty good right there.
47:38 Daniel Whiteson? Wow, you're coming out as anti-baby on the podcast. That's amazing.
47:41 Speaker 05 Seriously, what's cool about them is that I think they've gotten the short stick in terms of being just dismissed as living fossils, which yeah, they look a lot like they did back in the Cretaceous when dinosaurs were around. They've remained somewhat conservative over time, although there have been some groups of crocodiles that have come and gone even since the dinosaurs went extinct that were pretty darn weird.
48:05 Daniel Whiteson? And just to be clear, you're not making a political statement that conservative animals eat babies?
48:09 Speaker 05 No, not yet.
48:14 Speaker 05 Yeah, so crocodiles are just bizarre. They're not some sort of primitive thing. Everywhere you look at them, their body plan is incredibly specialized and modified. They're not like some holdover from some unspecialized, imperfect body plan. They're really amazing at what they are able to do. The way they breathe is really remarkable. They have this muscle that attaches to their pelvis that pulls their liver forwards and backwards, working like a piston to pull air in and out of their body, kind of like we use our diaphragm, but with a totally different mechanism. And they can produce the largest bite forces of pretty much any animal we know of. So they have gigantic jaw muscles toward the
48:59 Speaker 05 back of their jaws that can produce lots and lots of force. As I showed in some of my research, most species of crocodile can use these really extreme bounding and galloping gait that we would normally think of as mammalian-like kinds of movement. So they bend their backbones up and down instead of side to side and go airborne for substantial periods of time and can go pretty quickly
49:23 Daniel Whiteson? Wow.
49:23 Speaker 05 over ground. When they're small, at least. Once they get big, they seem to lose that ability. But yeah, they can be pretty great athletes. And so on and so forth. Man, I could go on and on about this. I just think they're really neat. And you might look at them and think, oh, that's just another lizard. Lizards are great in their own right, but a crocodile is not just an armored lizard or something like that. It's completely different. It's its own thing.
49:46 Kelly Weinersmith? I'm gonna say I'm a little jealous. In my field, the calls that we get are like, oh, hey, Kelly, I saw some really fresh roadkill. Do you want to come grab it? And like, the answer is always yes, because there's probably some really great parasites in there.
49:58 Speaker 05 Ah.
49:59 Kelly Weinersmith? This is a bunch of tapeworms from a roadkill porcupine.
50:02 Speaker 05 Ooh.
50:03 Kelly Weinersmith? Guys, I know, good stuff in my office here, but I don't have anything as cool as what you've got in my freezer.
50:09 Speaker 05 Well, you can always come visit and have a tour. I'd be glad to show you around. I've got ostriches, emus, there's a buffalo somewhere in there.
50:16 Daniel Whiteson? I've got a very Gary Larson image of your freezer going on right now with like, you know, ostrich heads sticking out and giraffe limbs everywhere. Is that pretty accurate?
50:24 Speaker 05 It's kind of like a frozen Noah's Ark, I guess you could say.
50:29 Kelly Weinersmith? That's awesome. I'm gonna see you in May.
50:32 Speaker 05 Okay, great.
50:34 Kelly Weinersmith? Yeah, I'm coming back to town in May. I'm gonna visit your freezers.
50:37 Speaker 05 Great.
50:37 Kelly Weinersmith? So what are the big open questions in your field right now?
50:40 Speaker 05 Oh, oh, oh, boy. Some of the ones we touched on earlier is like, what really limits size in animals? What limits speed in animals? How flexible is that? How flexible are those things? And how has that flexibility or the constraints on animals evolved over time with like changes in ecosystems, changes in animal tissues or what have you? I think there's still a lot that we can learn about what the range of possibilities is in animals. And the goal of my work that I've been really pushing on for a long time, and I think a good general goal for paleontology is that Paleontology should be able to teach us things about biology and contribute to theories
51:24 Speaker 05 in biology as a whole, not just be a slave to biology where we're always looking to biology, looking to nature today to try to solve questions about the past, but contributing to broader theories about animals in general through looking at the past and the present. So like my studies of how big animals are limited by their size and how athletic they can be, it's all about all these different groups, living and extinct. I don't care if they're living or extinct. I want to know what the principles are that we can derive from them. And I want to be able to prove to colleagues, regardless of what field they're in, that I can answer those questions and that we can learn something from a T. rex
52:04 Speaker 05 that isn't just, you know, a variant of what we already could learn from an elephant. That's a selfish example, just explaining what I would say is big questions.
52:15 Daniel Whiteson? Do you think there are big surprises waiting for us underground? You know, is it a possibility we could find a new huge dinosaur that blows your mind? I mean, we found like the Supersaurus and the Gigantosaurus and the Tyrannosaurus. Is there the possibility of some like uber megasaurus to be discovered? Or do you think we've sort of maxed out the size of dinosaurs?
52:34 Speaker 05 Or a hollow earth, like filled with giant sauropods?
52:37 Daniel Whiteson? Exactly.
52:40 Speaker 05 No, on the latter point, a very firm no there. But in terms of finding giant dinosaurs, yeah, I mean, over the last 20, 30 years, there have been larger and larger sauropods that have been found, including more and more complete ones. There's like seven skeletons of one really giant animal called Pitagotitan that I've worked with a small amount with colleagues on, and that's one of the biggest land animals ever. It's up there as a contender. And yeah, to have seven skeletons of that is really remarkable. But discoveries are pushing the boundaries continually. And we suspected that dinosaurs were feathered, but it wasn't until almost 30 years ago that we actually found out that many dinosaurs
53:23 Speaker 05 were from some pretty startling discoveries in China. So we know from the history of paleontology that there can be shocks there in terms of revolutions that can happen.
53:36 Speaker 05 Going up and digging fossils is always the primary lifeblood of paleontology. That's where discoveries ultimately come from. I don't do that kind of work. It's just not my skill set. I do the more lab or computer-based work where I'm trying to unravel what it all means. But yeah, I'm sure there's more surprises to come.
53:53 Kelly Weinersmith? It's time for the alien question, Daniel.
53:56 Daniel Whiteson? Well, it's always inspiring, I think, for listeners to hear that there are lots of mysteries left to unravel. And one mystery I think about a lot is what life might look like on another planet. And I wonder if you might speculate with us, because everything you've learned about comes from the experience here on Earth. And we don't know, of course, if this is typical, if we've explored all the effective possibilities that biology allows, or if life on Earth went down some weird little nook and most of life in the universe is different. It's all weird and hollow bubbles or something. So if we are about to land on an alien planet, and you're a biologist on board, what are you expecting to see in terms of large animals on the alien planet? And, you know, as an aficionado of monster
54:41 Daniel Whiteson? movies, feel free to go weird and crazy in science fiction.
54:46 Speaker 05 What would I expect to see? I'd be surprised if there were large animals. Well, it'd depend on what we would know about the planet. If it had been a place where the environment had been fairly stable for some time, given a long enough time for large animals to have evolved at all, and not having mass extinctions that screw it all up, then I might be more inclined to expect that. But anyway, all right, if I was expecting a big animal, well, I'd be wondering what's it supporting itself with? Are we going to learn something entirely new about supportive tissue? Like, is it gonna just not have anything remotely like muscle? Some other thing? Is it even a protein that's it's using to provide an active support? Or is it?
55:30 Speaker 05 I don't know, this, boy, the boundaries, the possibilities there get so interesting. And certainly depends on whether you are a carbon-based life form ultimately, or silicon, or whatever else they're using as their building box. And if they have DNA, what kind of DNA? Is it double-banded, triple-banded? Is it falling the same curvature as our DNA, or the opposite handedness? Does that even matter? I don't know. Or is it, are they using something totally different as heritable material? That would be a game changer for what evolution can even do. But I'm not sure I can give you a very satisfying answer for
56:12 Speaker 05 what I would expect in terms of animal life. It's so wide open for possibilities.
56:21 Daniel Whiteson? That's a pretty satisfying answer, honestly, to think that it's very wide open and we could be very surprised.
56:26 Speaker 05 I'd still expect the fundamental principle of the square cube law probably would hold if you got a wide enough size range of animals, that ultimately, if you push size to a large enough extreme on land where gravity's affecting organisms, then they're going to hit a limit and something's going to have to change. They're going to have to slow down, or really change their shape, or something like that. That would be a prediction that's really rooted in physics and fundamental theory of animal size and shape change. I'd feel pretty confident in that. But, I don't know, biology can screw things up, and maybe they change their molecules that they're made of as they go from small to big, and just break the rules of what we think is normal.
57:09 Kelly Weinersmith? Leaving on a high note here for Daniel, we can be sure about the physics, but the biology could screw things up. All right.
57:16 Daniel Whiteson? As usual with biology, it depends.
57:18 Kelly Weinersmith? It depends. Yes, that's the rule in ecology, at least. All right. Well, John, thank you so much for being on the show. That was a ton of fun, and I really hope I get to check out your freezer one day.
57:29 Speaker 05 Please do come. Yes, it's an open invitation for you both.
57:32 Daniel Whiteson? And if John ever serves you dinner, you should ask, what's in this burger?
57:40 Daniel Whiteson? Or don't ask.
57:41 Kelly Weinersmith? Yeah, I think don't ask is the way to go.
57:43 Speaker 05 You can ask. I won't be offended.
57:52 Kelly Weinersmith? Daniel and Kelly's Extraordinary Universe is produced by iHeartRadio. We would love to hear from you.
57:57 Daniel Whiteson? We really would. We want to know what questions you have about this extraordinary universe.
58:03 Kelly Weinersmith? We want to know your thoughts on recent shows, suggestions for future shows. If you contact us, we will get back to you.
58:10 Daniel Whiteson? We really mean it. We answer every message. Email us at [email protected] .
58:17 Kelly Weinersmith? Or you can find us on social media. We have accounts on X, Instagram, Blue Sky, and on all of those platforms you can find us at D and K Universe.
58:26 Daniel Whiteson? Don't be shy. Write to us.
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59:04 Speaker 01 That sound? That's pro squash. Some of the fastest rallies in sport played inches from the crowd. The National Squash League is back in full swing for season four. The sport is heading to the 2028 Olympics for the first time, and you can see it up close right now in a city near you. Watch every match for free on YouTube. Search National Squash League and hit subscribe or follow live updates on Instagram at nsl.sport. She's been thinking about this sleepover all week, but I think about her food allergies all the time. Fortunately, her doctor prescribed Zolair, omalizumab.
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