Was the Tyrannosaurus rex fast or slow? (Featuring Dr. John Hutchinson)

Daniel and Kelly talk to Dr. John Hutchinson about how large animals move. 

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Episode Transcript

Speaker 1 (00:05):
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 infraling to me,

(00:25):
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? If so,

(00:48):
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
around to be videotaped anymore? And the muscles that hold
keys to answering questions like these have long since decayed away. Well.

(01:08):
On today's show, we're talking to doctor 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.

(01:29):
Welcome to Daniel and Kelly's Extraordinarily fast Moving Universe.

Speaker 2 (01:47):
Hi. I'm Daniel. I'm a particle physicist, and I've always
considered myself a large animal.

Speaker 3 (01:53):
Hi.

Speaker 1 (01:53):
I'm Kelly Wiener 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.

Speaker 2 (02:06):
And so, Kelly, what do you think is your top
land speed or what could Kelly outrun? Let's put it
that way.

Speaker 1 (02:16):
I've definitely outrun some turtles on the property.

Speaker 2 (02:19):
And that's good. Let's start there.

Speaker 1 (02:21):
There are some fast frogs on the properties, so maybe
somewhere in between those things.

Speaker 2 (02:28):
Wow, are you telling me a swarm of frogs could
take you down?

Speaker 3 (02:31):
Oh?

Speaker 1 (02:32):
I mean they could catch up to me, but they're
pretty tiny, you know. I think I could give them
a couple good swift kicks. I have taken some taekwondo,
so maybe I can give them a couple of chops.

Speaker 2 (02:42):
All right, so all frog listeners be warned. Kelly can
defend herself. Yeah, 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 rather surprisingly fast. But to my credit,
I do have offspring surprisingly fast. My son is a runner,
and he runs a mile and shockingly four minutes and

(03:05):
twenty 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 transcription errors
or something that led to that.

Speaker 1 (03:16):
You're one of those parents whose children's accomplishments are your accomplishments.

Speaker 2 (03:21):
Absolutely, while I's have kids, I put his times on
my CV for sure.

Speaker 1 (03:28):
Does that help? What's funding? I can't imagine it would.

Speaker 2 (03:31):
It doesn't. No, it's wonderful to see your kids grow
up and just have different skills and interest than you do.
It's fantastic and also surprising sometimes.

Speaker 1 (03:41):
Yes, No, my son has amazing abs, Like you can
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 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.

Speaker 2 (04:00):
Our biology is complicated, right.

Speaker 1 (04:02):
They tell 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.

Speaker 4 (04:20):
Hi, there, Daniel and Kelly. It's been 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,

(04:41):
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 Evangelian anime,
which move really really fast. And it got me wondering,
is there any physics reason or any biol raisin why

(05:02):
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.

Speaker 1 (05:14):
So this is an amazing question. And I was so
excited when I 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 doctor John

(05:36):
Hutchinson on the show to tell us all about how
very large animals move and.

Speaker 2 (05:40):
What a giraffe burger taste like hmmm.

Speaker 1 (05:48):
Doctor 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,
Thank you very much.

Speaker 2 (06:07):
Kelly, Kelly in your introduction, you neglected to mention that
John also has an incredible array of heads on the
wall behind him.

Speaker 1 (06:16):
Well, I didn't know that when I wrote the intro.

Speaker 2 (06:18):
What's going on there?

Speaker 3 (06:19):
Yeah, that's my mask and collection. Oh cool, which got
particularly ironic early in the COVID pandemic, But it only
encouraged my collection of masks.

Speaker 2 (06:29):
So for those of you just listening, we see octopus
and what else is going on with giraffe?

Speaker 1 (06:35):
Thulu Giraffe? Are these all from places that you visited?

Speaker 3 (06:39):
Just random places, often just gifts from people, or I
find them like at a arts sale kind of thing
or whatever.

Speaker 2 (06:48):
I don't know why you don't just wear them when
you jump onto a zoom call. That'd be very dramatic.

Speaker 3 (06:54):
Some of them.

Speaker 1 (06:56):
All right, Well, let's pull back and talk about what
got you into in studying the movement of very large animals.

Speaker 3 (07:03):
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

(07:25):
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 growing
interest in science and my longstanding interest in the arts

(07:48):
and fiction. So I had to think about, Oh, wow,
that actually really makes sense, but too bad.

Speaker 1 (07:55):
And you were like, one day, I'm going to crush
dreams just like the author of that article.

Speaker 2 (08:00):
Yes, walk us to the argument, why does physics say
that biology can't get too big?

Speaker 3 (08:06):
The simplest explanation is what they call the square cube law. 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

(08:30):
metric of size more or less. But as your mass increases,
your area your linear dimensions squared, So cross sexual area
only goes up proportionately by the linear dimension squared, so
very quickly, the amount of weight you support on a
given area gets higher and higher and higher, unless you

(08:53):
do something to change your mechanics of movement.

Speaker 2 (08:59):
So let me interpret that. Assume, for example, we have
a spherical godzilla, right, solways like to assume spherical monsters.
Then you're saying the volume of that sphere goes with
the radius cubed right, it's like four thirds pi r cube.
But the surface area of the sphere is four pi
r squared. And so when you double the radius, the

(09:20):
volume goes up by eight, but the surface area only
goes up by four. And as that continues, as the
radius goes up and up and up, and you get
to actual gun zilla sizes, the ratio gets larger and
larger a 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?

Speaker 3 (09:39):
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 forest
per unit area a bone or a muscle can support
is fairly constant. A vertebrates that move on land in particular,

(10:03):
because this is all operating under gravity. Is assumption if
once animals get into 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.

Speaker 1 (10:20):
Is the limiting factor there mostly bone or mostly muscle,
or it has to be both. What limits what an
animal can hold?

Speaker 3 (10:28):
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's the living component, the contractile component of support, which

(10:49):
is muscle, But then there's all the other passive stuff bone,
ligaments and cartilage and so forth. It also provides 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,

(11:10):
I should specify land vertebrates, 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

(11:30):
quite unusual actually for animals of our size, and the
way we do that, it's very efficient, providing a lot
of passive support. So mostly the bones are providing allow
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. But you know,

(11:51):
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.

Speaker 2 (12:01):
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 godzillas.
But does that mean, for example, you couldn't have a

(12:23):
fundamentally different biology, you know, some crazy hollow thing or
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.

Speaker 3 (12:36):
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 what's there.

Speaker 1 (12:44):
So Daniel was asking, are there different ways to get bigger?
Like can you hollow out your inside or something you
mentioned in water is 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?

Speaker 3 (13:03):
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

(13:25):
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 are crashing,

(13:47):
all the time, like in the face of environmental change.
Then being big is a very terrible biological strategy, so
to speak. So large body size 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,

(14:11):
and that's arthropods. What's really interesting is that even in
the most extreme cases in the fossil record, we see
no gigantic arthropods.

Speaker 2 (14:21):
Remind me, what's an arthropod.

Speaker 3 (14:22):
Animals with exoskeletons, So insects, crabs, crustaceans, spiders, and so forth,
things with their skeleton on their outside.

Speaker 2 (14:30):
So no lobsters the size of blue whale so far.

Speaker 3 (14:33):
Yeah. Yeah. 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. They're a 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

(14:57):
are weirdos because their muscles break all the rule 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 still could not enable

(15:17):
like a fifty ton ant.

Speaker 1 (15:20):
Oh there was a movie when I was a kid
that had a giant ant after a new bar more
and yeah them, Oh, oh, you've crushed my dreams. I
was really hoping that that would be a silver lining.

Speaker 3 (15:31):
I think I specifically chose that to crush your dash man.

Speaker 1 (15:34):
Well, good job, good job.

Speaker 2 (15:36):
Spot on a little taste of your own medicine there, Kelly.

Speaker 1 (15:39):
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?

Speaker 3 (15:47):
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 and those three molecules
interact to produce these sliding filaments that lengthen and shorten

(16:07):
the muscle unit called the sarkamre. 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 studied things that

(16:27):
are really weird to me.

Speaker 2 (16:29):
Can I admit something that may be embarrassing? Yeah, 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 fifty ton ant, It's not just like a fire

(16:51):
hose of goo that's going to spread out.

Speaker 3 (16:53):
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.

Speaker 2 (17:13):
So are muscles conserved across all animals? Like everything that's
mobile on Earth uses some kind of muscle.

Speaker 3 (17:21):
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.
H 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

(17:42):
we're talking about muscle in the way that we're familiar
with it, with the three major components acting miosin Titan,
then that's an animal thing more or less.

Speaker 2 (17:50):
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
blue whale with a massive flagella behind it. Oh boy,
and hack, nobody's made that monster movie yet. That's the
real question.

Speaker 3 (18:06):
Yeah, Well, I mean the blob was kind of in
that direction of the I don't know how you classify
that blob, although if you know your HP lovecraft lore,
it was probably a shagoth anyway. Yeah, bacteria, I don't
know if I could give you an easy answer there.

(18:27):
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

(18:48):
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.
I mean, take a huge flagellum to move a big
bacterium through the water. I can't even imagine how the
mechanics of that would work.

Speaker 2 (19:07):
I'm sure you can imagine it. Mister monster movie over there,
for sure has the mental image.

Speaker 3 (19:14):
Give me a few million in VFX budget and I
can imagine it.

Speaker 2 (19:17):
Yeah, done and done.

Speaker 1 (19:20):
Yes, oh yeah, because we've got loads of money.

Speaker 3 (19:23):
James Cameron, There you go.

Speaker 2 (19:25):
Welcome to Daniel and Kelly's production studio.

Speaker 1 (19:28):
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.

Speaker 5 (19:42):
Oh, if possible, the gauntlet has been thrown down.

Speaker 1 (20:03):
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.

Speaker 3 (20:12):
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

(20:33):
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.

Speaker 1 (20:47):
That's where Daniel lives. Yeah, at the weird end.

Speaker 2 (20:50):
Yeah, I'm at the weird end of everything.

Speaker 1 (20:53):
That's right.

Speaker 2 (20:54):
But you ended up a biologist, I mean by name,
you're in the evolutionary biomechanics department, do you 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 then the other, like, why are biologists more likely

(21:15):
to hire you than physicists?

Speaker 3 (21:17):
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,

(21:41):
I couldn't go work in a physics department. They could
tell that I was an impostor.

Speaker 2 (21:46):
Now 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.

Speaker 1 (22:00):
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?

Speaker 3 (22:20):
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 haven't been that much
research on how the biggest land animals worked. So I
do work on living animals using like X ray machines.

(22:42):
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 it's skeleton

(23:04):
moving in life. It's been a big game changer over
the last twenty 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

(23:25):
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 environments, so what we call force platforms

(23:48):
and pressure pads that measure the force per unit area
they apply to the grounds. 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.

Speaker 2 (24:02):
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?

Speaker 3 (24:14):
Also, you can't have them moving around with like a
video camera going on capturing data the a CT scan,
you have to have individual remaining still because you're taking
cereal slices cerial X rays of the individual to them
piece together the whole three D person. So if they move,
actually your image gets screwed up.

Speaker 2 (24:33):
I see. You can't convince an elephant to stay still.

Speaker 3 (24:36):
Yeah.

Speaker 1 (24:37):
Yeah, what's the biggest animal that you've studied.

Speaker 3 (24:40):
I've worked a bit on the big stopod 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 pal petology fans rather upset, but it was

(25:02):
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 it's ken. I've worked on
living elephants from zoos around the US and UK to
more wild type elephants in Thailand, working with elephants that
were either previously used in logging or tourism, or even

(25:24):
used in racing. So I got to measure how the
fastest elephants could move, which was really really cool.

Speaker 2 (25:31):
How fast can the elephant move?

Speaker 3 (25:33):
They can go up to almost fifteen miles an hour,
which might not sound that fast, but that's a challenge
for me to keep up with that pace. It's still
pretty impressive to see like a four thousand kilogram animal
traveling at fifteen miles an hour.

Speaker 2 (25:50):
That's a lot of kinetic energy.

Speaker 1 (25:51):
I bet it feels really fast if it's chasing you.

Speaker 3 (25:54):
Oh yeah. What we found with that work was that
even though elephants don't go born 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 mid air. So that was really cool to

(26:15):
see how extreme the gate of elephants could be. They
really do move in rather extreme ways even though they
don't go fully airborne.

Speaker 2 (26:22):
That's fascinating. You talk about the gate of elephants like
whether they're ever have all four legs off the ground. Yeah,
animals do ever have all four legs off the.

Speaker 3 (26:31):
Ground 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 three thousand kilograms or so, so

(26:54):
rivaling the size of some like Asian elephants, they can gallop,
they can leave the grind with all four feet, so
they are kind of in that zone of being big
and being athletic that is apparently hard to achieve.

Speaker 2 (27:08):
You discovered flying rhinoceurces. That's amazing.

Speaker 3 (27:12):
The rhino thing was known, but the fine hippo thing
that was a small new contraction that I'm still proud
of and got a lot of news attention. I was
really kind of pleasantly surprised by that.

Speaker 2 (27:23):
I want to come back to the 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 of 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 service area without increasing your volume. Is that

(27:46):
pop science nonsense or is that real science?

Speaker 3 (27:48):
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 it
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

(28:10):
the overall large ear size and elephants overall relates to
them using the ears as the cooling mechanism, and they
do wave their ears so they get convective cooling, moving
the air quickly passed to ensure that there's always more
air to unload the heat onto as they keep airflow going.

Speaker 1 (28:29):
And mammoths had little ears, right.

Speaker 3 (28:32):
Some wooly mammoths did, so. There are quite a few
different species of mammliths. The wooly moth is the one
we know best from animals preserved in frost, and Siberia
had a lot of body parts reduced to avoid frostbite.

Speaker 2 (28:45):
Probably you know, I noticed that in Farside 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.

Speaker 3 (28:56):
Oh he needs science. Yeah, he paid attention.

Speaker 1 (29:00):
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?

Speaker 3 (29:12):
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 post doc 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?

(29:33):
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 the 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

(29:53):
made it into kind of a game for them or
a contest. So each elephant has its own companion, a
mahout or a rider who pretty much grows up with
the elephant, and they have a very strong bond in Thailand.
And so the mahout would encourage the elephant by whatever
means he thought was reasonable, like calling to it usually

(30:14):
or having someone run in front of it, or have
it go toward a friendly elephant, and that would motivate
it to go quickly. It certainly did work in Thailand.
We got much faster elephants than we ever did elsewhere.

Speaker 1 (30:27):
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. It's a very unique problem.

Speaker 3 (30:36):
This is animal research. Yeahm Motivating animals very challenging.

Speaker 1 (30:40):
It's true.

Speaker 2 (30:41):
Do you have to get an IRB there, like do
elephants get grumpy if you make them run, or can
you probably hurt them or something.

Speaker 3 (30:48):
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? Will you terminate
the experiment? What does stress look like? There are important questions,
and avoiding fatigue also is really important. So we give
animals lots of risk because we don't want to study fatigue.

(31:09):
We want animals that are fresh.

Speaker 1 (31:11):
Let's go back to dinosaurs. You mentioned t rex right
after we have 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?

Speaker 3 (31:26):
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

(31:47):
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 very
simple or very complicated mechanical model of a dinosaur for
its own sake. So actually try to reconstruct, like in
a computer usually what the animal looked like, it's dimensions,

(32:10):
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

(32:32):
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 twenty five miles an hour,
but still possible to do more like kind of elephant speeds,

(32:53):
maybe fifteen miles an hour, which for an animal that
could get bigger than an elephant, it's still pretty darn good.

Speaker 2 (32:58):
So what you're doing here is 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 then studying that.

Speaker 3 (33:12):
It's setting up a set of constraints. So here's what
it'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

(33:34):
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 to guide their lines of action. And that

(33:55):
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

(34:17):
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 muscler tendon and the
bone itself.

Speaker 2 (34:29):
When you say conservative, you mean similar across species. Yeah,
in small government.

Speaker 3 (34:35):
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

(34:56):
animals and this information that we have directly from the skeleton.

Speaker 2 (35:00):
The physicists in me likes that you're like building a
model and exploring the speed and motion of that model,
but then also wonders like what do we know about
how that model might differ from real blinosaurs? 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,

(35:22):
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.

Speaker 3 (35:30):
It is difficult to make very specific predictions, and I
mean quantitative arguments are always in some very rough bounds
of possibilities. So like trying to predict the speed doesn't
extinct on us, or we don't even know for sure
what the bounds can be. But we can do what
we'd call sensitivity analysis, or the different inputs we put
into the model, So how big are the leg muscles,

(35:53):
where are they attached to, so on and so forth,
and then see what the output of the modeling analysis is, Well,
how does that change running speed if we change these assumptions.

Speaker 5 (36:03):
In the model.

Speaker 3 (36:04):
Another thing we do that's really important, and this is
where my training in biology really comes to bear and
my work with living animals is we can apply the
same methods 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

(36:27):
of tests, they usually do pretty darn well. So we
can predict that a bird can run by ped lee,
whereas a crocodile that doesn't run by p Lee cannot.

Speaker 2 (36:35):
That's very cool that you apply your mechanism to animals
where you can check yourself.

Speaker 3 (36:39):
That's very cool, very important.

Speaker 2 (36:41):
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 fifteen 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
to tell us that a lot of what we're assuming,

(37:02):
that the assumptions we're making might be changing with time
and might have uncertainties we haven't accounted for.

Speaker 3 (37:07):
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

(37:28):
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 that inputs completely, or changes
the way we should even model the whole thing completely
the way the whole system might work, and so they
could repeat or do a completely new invention of that
kind of analysis. I think that's the key.

Speaker 2 (37:51):
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 change people minds about why they couldn't go quickly?

Speaker 3 (38:02):
Living land animals, no matter of 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. And the upper limit of that muscle

(38:22):
mass that we can see in nature appears to be ostriches.
Large per 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,

(38:45):
Nothing like a t rex was built to have a
body devoted to muscle like an ostrich does today. So
we could use an ostriches like an upper limit for
what we know of in terms of how much muscle
a dinosaur might have had. Even that that would be
a bit straining credulity if we did say a dinosaur
had that much muscle.

Speaker 2 (39:05):
Are you saying an ostrich would beat any dinosaur in
a foot race?

Speaker 5 (39:09):
Yeah?

Speaker 3 (39:10):
Yeah, I think it probably would. But even ostriches have
more muscle devoted to their limbs than like past animals
like cheetahs or big animals like rhinos or elephants do.
They're super muscular animals.

Speaker 1 (39:21):
All right, So let's take a break, and when we
get back, we're gonna hear about some weird stuff that's
been in John's freezer.

Speaker 2 (39:27):
Oh, As someone who is married to biologist and has
weird stuff in his freezer, as a result, I am

(39:49):
terrified to learn what John might have in his freezer.

Speaker 1 (39:54):
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.

Speaker 3 (40:10):
The glory days are gone you 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 walking freezer. But yeah, I mean, over the years,
I've had a lot of parts of elephants because elephants

(40:32):
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 contribute to taking care of animals like elephants. A

(40:55):
lot of elephant parts, rhinos never had a hippo of drafts,
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.

Speaker 2 (41:09):
What's to love about crocodiles?

Speaker 3 (41:11):
Sorry, guys, Oh, they're so so bizarre.

Speaker 2 (41:16):
I've 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?

Speaker 3 (41:30):
Well, just that it means that's pretty good right there.

Speaker 2 (41:35):
Wow, you're coming out as anti baby on the podcast.
That's amazing.

Speaker 3 (41:38):
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

(41:58):
since the dinosaurs went that we're pretty darn weird.

Speaker 2 (42:01):
And just to be clear, you're not making a political
statement that conservative animals eat babies.

Speaker 3 (42:06):
No, not yet. 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 pulled over from some unspecialized, imperfect body plan.

(42:29):
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

(42:49):
they can produce the largest bite forces of pretty much
any animal we know of, So they have gigantic jaw
muscles toward the back of their jaws that can produce
lost lots of force. As I showed in some of
my research, most species of crocodile can use these really
extreme bounding and galloping gates that we would normally think
of as mammalian like kinds of movement. So they bend

(43:12):
their backbones up and down instead of side to side
and go airborne for substantial periods of time, and can
go pretty quickly overground 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

(43:32):
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. That's
completely different. It's its own thing.

Speaker 1 (43:42):
I gotta say 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. This is
a bunch of tapeworms from a road killed porcupine. I
know good stuff in my office here, but I don't
have anything as cool as what you've got in my freezer.

Speaker 3 (44:05):
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.

Speaker 2 (44:13):
I've got a very Gary Larsen image of your freezer
going on right now with like you know, ostage head
sticking out and giraffe limbs everywhere. Is that pretty accurate?

Speaker 3 (44:21):
It's kind of like a frozen Noah's arc. I guess
you could say this.

Speaker 1 (44:26):
That's awesome. I'm going to see you in May. Okay, great, Yeah,
I'm coming back to town in May. I'm going to
visit your freezers. Right So, what are the big open
questions in your field right now?

Speaker 5 (44:36):
Oh?

Speaker 3 (44:38):
Oh boy? Some of the ones we touched on earlier
is like, what really limits size in animals? What limit
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

(45:00):
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 paletology is that palingtology should be able to teach
us things about biology and contribute to theories in biology

(45:21):
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

(45:43):
the athletic they can be, it's all about all these
different groups living in 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 that
isn't just you know, a variant of what we already

(46:04):
could learn from an elephant. That's a selfish example, just
explaining what I would say is big questions.

Speaker 2 (46:11):
Do you think there are big surprises waiting for us underground?
You know? Is it possibility we could find a new
huge dinosaur that blows your mind? I mean, we found
like the Supersaurus and the Gigantosaurus and the Titanosaurus. 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.

Speaker 3 (46:31):
Or a hollow earth like filled.

Speaker 2 (46:32):
With giants exactly.

Speaker 3 (46:37):
No on the latter point, A very firm no there.
But in terms of finding giant dinosaurs, yeah, I mean
over the last twenty thirty years, there have been larger
and larger sore pods that have been found, including more
and more complete ones. There's like seven skeletons of one
really giant animal called protagotitan that I've worked with a
small amount with colleagues on and that's one of the

(46:59):
biggest and animals ever. It's up there as a contender.
And yeah, to have sudden 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 thirty
years ago that we actually found out that many dinosaurs

(47:20):
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. Going
up and digging fossils is always the primary lifeblood of paleontology.
That's where discoveries ultimately come from. I don't do that

(47:40):
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.

Speaker 1 (47:50):
It's time for the alien question. Daniel.

Speaker 2 (47:53):
Well, it's always inspiring. I think for listeners to hear
that there are lots of mysteries left to unravel. And
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

(48:14):
the effective possibilities that biology allows, or if life on
Earth went down some weird little nook and most of
life in the university 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 an alien planet? And you know, as an

(48:37):
efficionado of monster movies, feel free to go weird and
crazy in science fiction.

Speaker 3 (48:42):
What would I expect to see? I'd be surprised if
there are large animals, Well, it depends 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 screw it
all up, then I might be more inclined to expect that.

(49:05):
But anyway, all right, if I was expecting a big animal,
well I'd be wondering what's 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 I

(49:27):
don't know this boy. The boundaries that 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 to following the same curvature as

(49:51):
our DNA or the opposite handedness? Does that even matter?
I don't know? Or are they using something totally different
as heret 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 what I
would expect in terms of animal life. It's so wide

(50:15):
open for possibilities.

Speaker 2 (50:17):
That's a pretty satisfying answer, honestly, to think that it's
very wide open and we could be very surprised.

Speaker 3 (50:22):
I'd still expect the fundamental principle of the square cube
LA probably would hold if you've got a wide enough
size range of animals that ultimately, if you push size
to it large enough extreme on land where gravity is
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

(50:45):
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. There
are molecules that they're made of as they go from
small to big and just break the rules of what
we think is normal.

Speaker 1 (51:06):
Leave it on a high note here for Daniel, we
can be sure about the physics, but the biology can.

Speaker 2 (51:10):
Screw things up all right, As usual with biology, it.

Speaker 1 (51:14):
Depends its Yeah, so that's the rule in ecology at least.

Speaker 5 (51:19):
All right.

Speaker 1 (51:19):
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.

Speaker 3 (51:26):
Please do a comment. Yes, it's an open invitation for
you both.

Speaker 2 (51:29):
John ever serves you dinner, you should ask what's innsburger?
Or don't ask?

Speaker 1 (51:38):
Yeah, I think don't ask is the way to go.

Speaker 3 (51:39):
You can ask, I won't be offunded.

Speaker 1 (51:49):
Daniel and Kelly's Extraordinary Universe is produced by iHeart Reading.
We would love to hear from them, We really would.

Speaker 2 (51:55):
We want to know what questions you have about this extraordinary.

Speaker 1 (52:00):
Want to know your thoughts on recent shows, suggestions for
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Speaker 2 (52:07):
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