[00:00:00] SPEAKER 1:
And, uh, we’re pleased to have all of you here today. Thank you so much for joining us. It’s my pleasure to introduce, uh, Andrew Szeri.
(applause)
[00:00:12] ANDREW SZERI:
Good afternoon. Uh, my name is Andrew Szeri. I’m Dean of the Graduate Division, and we’re pleased, along with, uh, Graduate Council, to welcome you, uh, to the Charles and Martha Hitchcock Lecture Series.
Our speaker today is Neil Shubin. The story of how the endowment came to Berkeley, um, is a nice example of the ways in which this campus, uh, is linked to the history of California and of the Bay Area. Dr. Charles Hitchcock was a physician, uh, for the Army and came to San Francisco during the Gold Rush, where he opened a thriving private practice.
In 1885, Charles established a professorship here at Berkeley as an expression of his long-held interest in education. His daughter, Lillie Hitchcock Coit, still treasured in San Francisco for her personality as well as her generosity with respect to towers, greatly expanded her father’s original gift to establish a professorship at Berkeley, making it possible for us to present a series of lectures. The Hitchcock Fund has become one of the most cherished endowments of the University of California, recognizing the highest distinction of scholarly thought and achievement.
Now, I would like to invite William Lester, Professor of Chemistry and Chair of the Hitchcock Professorship Committee, to say a few words about our speaker, Professor Neil Shubin.
[00:01:29] WILLIAM LESTER:
Thank you.
(applause)
Well, thank you, Dean Szeri. Good afternoon. Although you’ve heard it before, I’m William Lester, Professor of Chemistry and Chair of the Hitchcock Professorship Committee.
On behalf of the Hitchcock Committee, I’m pleased to welcome Neil Shubin as this year’s speaker in the Charles M. and Martha Hitchcock Lecture Series. Neil Shubin is a distinguished paleontologist whose research seeks to understand the mechanics behind the evolutionary origin of anatomical features of animals. His work focuses mainly on the Devonian and Triassic periods to understand the pivotal ecological and evolutionary shifts that occurred during that time.
In two thousand four, after scouring the Canadian Arctic for six years, Shubin and his team unearthed Tiktaalik roseae,
(unintelligible)
a fossil fishapod which despite its fish-like features, had a neck, skull, ribs, and parts of limbs similar to land animals. This discovery represents the transition between fish and four-legged mammals that occurred over three hundred and fifty million years ago. His announcement about the discovery of this phenomenon on April sixth, two thousand and six in the journal Nature, made front-page news in newspapers worldwide.
Finding the three hundred and seventy-five million-year-old fossil also spurred Shubin to write the recent book, Your Inner Fish, A Journey into the Three and a Half Billion Year History of the Human Body, arguing that fish provide an important evolutionary step in human history. Shubin received his BA from Columbia University in nineteen eighty-two. He earned his PhD from Harvard University in organismic and evolutionary biology in eighty-seven.
And in nineteen ninety-six, he was awarded an honorary MA from the University of Pennsylvania. He was a Miller Postdoctoral Fellow at UC Berkeley from 1987 to 1989, and held positions as an assistant, associate, and full professor of biology at the University of Pennsylvania before joining the faculty of the University of Chicago in 2000. Shubin is currently the Robert R. Bensley Professor of the Organismal Biology and Anatomy.
He serves as the Associate Dean of the Biological Sciences Division and as a member of the Committee on Evolutionary Biology. Shubin has been honored with the Guggenheim Fellowship, the Marcus Singer Award, and was named Person of the Week by ABC News for the week of April 7th, 2006. In addition, he has appeared on The Colbert Report and Public Radio International.
Please join me in welcoming Professor Neil Shubin.
(applause)
(applause and laughter)
[00:04:37] NEIL SHUBIN:
Thank you, uh, Dean Szeri, uh, Professor Lester, members of the, uh, Hitchcock Committee, uh, my hosts in the Department of, uh, of Integrative Biology here at Berkeley. Thank you for the honor of being a Hitchcock professor, and thanks also for giving me the opportunity to return to Berkeley, which is my intellectual– which is the place of my intellectual roots. Much of what I do, uh, is really sort of flowed from, uh, the concepts, ideas, and approaches that I learned during my time here, uh, at, at Berkeley.
So today we’re going to talk about the Great Transformations, and if you take the four and a half billion year history of our planet, you can begin to visualize it in a number of different ways. And one of the most common ways to visualize the history of our planet is as some sort of linear series of events. And so this is one taken from a textbook.
Uh, it’s, uh, from Press and Siever, a, one, a very prominent geology textbook. And what you see is, you know, it’s this linear series is depicted as sort of a corkscrew so they can, you know, fit it on the page. And, um, and, you know, you see the various events and the trajectory in the history of our planet and the history of life on our planet.
You know, from the, uh, from the presence of the first rocks, the, the earliest visible life in the fossil record, the origin of, uh, bodies and plants and animals. And then you see sort of the major events in the history of, uh, of vertebrate life, creatures with, with bones. The, the shift from water to land, the, the shift, to the origin of dinosaurs and so forth.
When you look at the world this way, in this sort of linear way from beginning to present, what you sort of see is there are times that kind of look revolutionary, where there’s sort of revolution in the air, where there big things happening. And those time periods have always attracted my attention for one reason or another. And, and that’s why I’ve ended up focusing on sort of two time periods in the history of life, the, the Triassic and the Devonian.
Uh, time periods from two hundred million years ago and about three hundred and seventy-five, uh, million years ago. But anyway, I, I’m gonna show you how this kind of way of depicting the history and the sequence of events in our world actually is, is– it gets in the way of really understanding and decomposing some of the main events we see in the history o-of our planet and life on our planet. And with the one I’m gonna do is I’m gonna take one particular example, one major transformation, the shift from fish that lived in water to limbed animals that, that live on land.
I’m gonna take that shift and really analyze it in detail to show you how an integrative approach, integrating fossils and studies with living organisms, can tell us a lot about how this transformation happened. And I’m gonna use that as a microcosm as an example, really, of, uh, of how we can approach all the other transformations, uh, that are out there. So let’s start with the transformation from water to land.
So here what you have is, uh, sort of the transformation from water to land. And, um, you see here, I’ve sort of shown a cartoon. This is a complete caricature of the situation.
And if you were to sort of blue sky this thing, in the back of an envelope and, you know, look at a fish and look at a land-living vertebrate animal with bones, uh, you can sort of say, ‘Wow, geez, life in water is vastly different from life on land.’ Almost every single system of these creatures had to change. And I just sort of showed you several here.
I mean, respiration, feeding, locomotion, and head mobility. And if you look at the end states of this transition, it looks really large and, indeed, almost impossible. Let’s just take a few of them.
Take respiration. I mean, you have a shift from creatures that are largely water-breathing to creatures that are air-breathing. This involves whole suites of changes to organs and the ways that organs develop and, and circulatory systems and lungs and so forth.
Feeding. Feeding in, uh, water is very different from feeding on land. Um, you go from a, where we have water, where you can suck the, uh, uh, food, uh, into the mouth by changing the volume of the mouth cavity, uh, to, to biting, where on land you can’t suck in unless you’re a Hoover, you know, Dustette or a, a vacuum cleaner.
Um, it’s, it’s really more of a biting, uh, uh, approach to, uh, um, um, capturing and, and chewing food. Locomotion is completely different on land, uh, from water. I mean, here you have water supported, but where basically you have to support yourself in gravity.
That’s not gravity supported, but it’s, uh, you know, it’s basically you’re dealing with gravity as a force, and the skeleton had to change, uh, from a water supported to actually dealing with gravity as a, as, as a force, um, on the ground, on the substrate. And there are all kinds of other changes associated with this. Head mobility, you know, fish have heads that are largely connected, uh, to the body.
Uh, uh, the, uh, with, uh, by a series of bones so that when you move the head, you move the, the rest of the body. Uh, they don’t have necks, whereas land-living creatures have necks, where the head can move independently of the body. Now, for this whole talk, I could have gone through a whole long list of things from excretion, reproduction, and all kinds of different systems that would have to change.
And when you look at these systems, you’d say, “Golly gee, uh, I don’t see how this transformation can ever happen.” So my real– my sort of goal for the last twenty years has really been to look at this in detail, to try to collect new fossils, to try to collect understandings from living recent creatures that tell us a lot about how fish, uh, uh, did, uh, uh, achieve this important shift in evolution. This was sort of the state of affairs in 1987.
This was a textbook written by one of my, uh, predecessors at the University of Chicago, Len Radinsky. Um, a- and, and I saw this in 1987 in a graduate, um, seminar, and it really attracted my interest, Because what he showed is a lobe-finned fish on the top. This is a creature from about…
The first ones of these appear about three hundred and eighty million years ago. And on the bottom, uh, you see an early limbed creature. This is a creature from Greenland, uh, at least what we thought it looked like at the time, uh, from about three hundred and sixty-five-ish or so million years ago.
And I remember looking at this and saying, “Golly gee, this is a big transition. There’s a lot of features that have to change.” And to approach this, it became pretty clear that if we wanted to address this, we had to go find new fossils.
In fact, if we wanted to find new fossils that bridged this gap, we’d have to find whole new places to look for fossils. So off we went to start looking for places to find new fossils that tell us about this important anatomical shift. And so like paleontologists everywhere, there are actually some simple rules to go when you want to design a new expedition to look for, uh, uh, fossils.
We look for places in the world that have sort of a convergence of three things. Uh, the first is, you look for places in the world that have rocks of the right age to answer the question that you’re interested in. I mean, so I’m interested in the shift from water to land.
And fish, so it’s no mystery that I’m interested in rocks around three hundred and eighty to three hundred and sixty-five or so, uh, million years old. The next thing is you look for rocks of the right type. Not every, not every kind of rock, uh, preserves fossils.
Uh, sedimentary rocks preserve fossils better than volcanic or metamorphic ones. And indeed, within the sedimentary rocks, there are certain, uh, depositional environments, environments where those rocks were formed, which are more likely to preserve fossil bone than others for a variety of reasons. One, because they might reflect areas where creatures lived.
Uh, the other is because they w-were formed in very gentle, um, uh, uh, environments with little erosion so that whatever fossils were there were, were preserved in, in some detail. The third variable is really important, actually it’s one of the most important ones. It, it does me no good if my wonderful rocks of the right age and the right type are buried five miles underground.
I mean, these rocks have to be exposed to the surface. I mean, what we do as paleontologists is walk over rocks for long da– long days to find bones weathering out. Uh, so it’s really exposures, rocks of the right age, and rocks of the right type.
There’s a third variable when I started out on this quest, and that was, uh, lack of money. And so I started, um, my… It was really true.
I started my, um, first academic job after leaving Berkeley as a Miller Fellow. I, um, I moved to Philadelphia as a young assistant professor, um, here in the southeastern portion of the state. And what I wanted really was a, um, a field program that I could do on the cheap or on weekends out of my car.
You know, paying like turnpike tolls and gas money. And the first thing I did was obviously pulled out a geological map of New York and Pennsylvania, and the first thing you see when you pull out a geological map of New York and Pennsylvania is you see that the place is just littered with Devonian Age rocks. So I basically stripped out everything, um, in, unimportant out of the state of Pennsylvania, and what’s left here is the Devonian.
And, and you can see, I mean, it’s loaded with Devonian Age rocks. And these span in age pr- mean, pretty much in the late Devonian is the ones I was, uh, interested in, and these were rocks about three hundred and sixty-five million years old from the Catskill Formation, and they extended into New York into the Catskills, hence the name. So it was pretty clear f- from about a three-hour drive from Philadelphia, um, you know, I had access to, uh, Devonian Age rocks.
It get, got even better when we started to look at the geology of these rocks and what geologists knew. The Pennsylvania State Geological Survey was mapping these rocks for years and, and concocted a cartoon, really, version of what Pennsylvania was like at this time. If you wanna think what Pennsylvania is like in the Devonian, get Pittsburgh, Harrisburg, and Philadelphia out of your brain, and think Amazon Delta.
This is really a cartoon of, of the reconstruction. Essentially a, um, a series of highlands to the eastern part of the state of Pennsylvania and an inland sea to the west called the Catskill Sea. So if you look at the Devonian rocks of Pittsburgh or Cleveland, you’ll find there, you know, uh, uh, marine rocks, uh, for this inland sea, and a series of rivers that drain from east to west.
Now, if you’re a paleontologist interested in the transition, uh, from fish to limbed animal, and you want to find fossils along this line, this is perfect because you can sample, if you’re lucky, uh, ancient seas, ancient estuaries, all the way u-up the stream, if you’re lucky. I was also lucky in this, uh, regard because I… A graduate student started working with me.
Uh, this is Ted Daeschler here. This is a picture of us last year, not when he was a graduate student. We were a lot younger when this whole thing started.
Um, but… And Ted and I have been working ever since, and Ted really has, uh, been a major, major, major part of much of the work you– f-fossil work you’re going to hear about. But Pennsylvania has a problem.
I mean, it has two of these variables. It has, you know, rocks of the right age and rocks of the right type. But unfortunately, it’s not renowned for its exposures.
Uh, Pennsylvania is not a desert. And so it turns out the best exposures for us were areas where the Pennsylvania Department of Transportation decided to put in new roads. What would happen, uh, or where there were streams, but It was actually the road cuts that were kind of the critical thing.
Uh, what happens is, you know, PennDOT will come through and, you know, when they wanna put a road or a bend in a road or widen a road, what would they do? They’d blow it up, right? Blow up rock.
When they blow up rock, if we were really lucky, they’d blow up rock in the Devonian. And if we were super really lucky, they’d blow up rock in, you know, the right, uh, part of the, uh, the delta system of the Devonian rocks. And this is one area where… which was widened in the ’70s.
It’s a, it’s a road about an hour north of State College, Pennsylvania. It’s a road cut called, don’t, don’t be surprised, Red Hill, because it’s a red hill. Um, large road cut.
When it was widened in the ’70s, um, it exposed a series of the strata, the beds here, which you can see going up. This is really a fluvial or river environment, and what you see as you walk through here are sort of cross-sections of ancient streams. Ancient streams, their overbank or marginal deposits.
Sometimes you’ll see point bars. These streams look like they meander. It has a very classic sort of deltaic, uh, even part of a m-
A- A- And some meandering streams, uh, within this area, so it’s a really rich area. And you see the scale here.
Uh, there is a car and there’s a human being for scale. What essentially our research program was, was to climb up and down the sides of these hills. It got a little tricky, but pretty soon, by about 1991, we started to find, uh, all kinds of fossils.
I mean, the first things we started to see were like teeth the size of railroad spikes coming out of the, the hills here. We started to find jaws of these creatures, and this is a Ted holding like one of our first jaws we found out of this thing. It was just the front end of a jaw.
These jaws are about as long as your arm, um, and, you know, with teeth the size of your thumb. So there’s a really big monstrous fish that are about sixteen feet long. You know, up to sixteen feet long.
So large carnivorous fish coming out of the rocks, uh, uh, here. We had lots of other kinds of fish and invertebrate animals. Um, we have this, uh, this is a sidewall of a fish with…
You can see its body armor. It’s got a squashed head here. Tons of these kinds of things.
And then by about 1993, we started to find bits and pieces of early limbed animals, and this was one that was particularly important at the time. It’s an upper arm bone, a humerus, and we started to find a, a femur, which is an upper leg bone. We found other bones of the skull and so forth, and this humerus was particularly important because very, s– it was very s– it was very similar to that, uh, humerus, a humerus, humerus known from a, a Devonian limbed animal from, uh, from Greenland, one actually I showed you in a cartoon earlier.
So it was pretty successful. We started to find, by the mid-’90s, a whole ecosystem really. And I’m not even describing the plants.
Some of the earliest known forests with trees, and we’d find their leaves and trunks and so forth.
(cough)
Uh, land was loaded with lots of life, uh, scorpion-like and spider-like creatures, and many of those from these sites, and then tons of fish, uh, from within here. And this is what this road cut, uh, Red Hill road cut in Pennsylvania looked like when we reconstructed it with National Geographic. Um, you know, you have that large fish, you know, with the teeth the size of railroad spikes.
You have lots of little armored fish around here. And then you have these limbed animals, the, with the tetrapods, literally four-legged creatures, of which there are about three or four types coming out of here. It’s really remarkable.
But it became really clear that to get to the problem that I was interested in, this transition, we weren’t making a ton of headway. We were finding tons of fossils, but these rocks were about three hundred and sixty-five million years old, and what we were picking up at this point were mostly really well-formed tetrapods. Uh, we were picking up some of these creatures as well, but from our knowledge of the rocks and faunas around the world, it was pretty clear we were probably in rocks too young.
We would have had to move back in time. Because to move back in time, we’d be begin to understand some of the transition here, and I just want to run through some of the anatomy that’s different. You know, here you see the lobe-finned fish on top, which we knew was closely related to limbed animals, and you just look at the head.
You see basic differences in the, you know, architecture of the head. You know, here at the top, you see, you know, these creatures have a, like a conical head with eyes on either side. Um, the early limbed animals have look almost like a crocodilian kind of head.
It’s a, it’s a flat head with eyes on top. And the architecture of the bones in here actually is, is, is, is somewhat different than the, uh, than the, the fish on top as well. If you look at the neck, fish don’t have a neck.
Again, as I said before, the head is actually connected to the shoulder via sort of linkages of bones. Um, and the head is not independently movable, whereas in early limbed animals, like all their descendants, you and I, um, have a neck where the head is separate from the shoulder and then there’s a series of joints in the base of the, in the base of the skull. And, you know, and finally, I mean, I can make a long list here, but the, the thing that was really interesting to me was to understand the shift from fins to limbs.
Uh, fish have fins with fin webbing. You lose the fin webbing when you get to these early limbed animals, and you gain fingers and toes and wrists and ankles. Okay?
And we weren’t making a whole ton of headway in understanding this transition. And it became very clear from what we knew, and this is what we were finding, this is the family tree, more or less. Here’s limbed animals up here.
Uh, these are the fish that are successfully mostly closely related to them. If we wanted to make any headway, we had to find creatures that are sort of more on this branch, which would really be able to sort of very clearly tell us the sequence of key s– the origin of key s- features that, uh, led to the origin of limbed animals. And to do that, when we look at the, the age of these things, these things, many of these first appear back around three hundred and eighty, three hundred and ninety million years ago.
Some of them continue all the way up. The earliest, uh, limbed animals, tetrapods, appear about three hundred and sixty-three, three hundred and sixty-five million years ago. At least, the good skeletal material at the time, which is what we knew.
But there was a big gap in our knowledge. We didn’t have many faunas or floras at this age, really, here at about three hundred and seventy-five million years ago. So we had to move back, uh, in time.
And so we began our hunt again, right? So you look… Remember, we look for rocks of the right age, rocks of the right type, and exposures.
And going through it, it became pretty clear we had to, um, we were thinking about going to Brazil, we were thinking about working in, uh, Colorado. Everything changed for us one day in the winter of nineteen ninety-eight, in my office at the University of Pennsylvania. Um, Ted and I were having an argument, and to settle the argument, I pulled out a college undergraduate geology textbook.
This, um, this is, I think, one that I had. It was the second edition of Dott and Batten, Evolution of the Earth. I believe it was pre-plate tectonics when it was written.
This book is now, I think, in the eleventh edition or something like that. We settled the debate, and as I was stumbling through the book after, um, after that little uh, set-to, I came upon this figure in the textbook in, like, chapter fourteen, and it stopped me in my tracks and basically defined my research, at least in the field, for the next six years. So I wanna spend a second on this, uh, diagram.
It’s that important. It says Upper Devonian sedimentary facies, which means, you know, rocks more or less of the right age, and who knows, maybe rocks of the right type. And what you see here is a map of North America.
Here’s the United States, here’s Mexico, here’s Canada, Greenland, Canadian Arctic, and superimposed on that is a map of the depositional environments, or the environments of rock formation in the Devonian. And the western part of North America was mapped as an ancient ocean. Uh, for– the rocks there were formed, in the Devonian at least, were formed in an ancient ocean.
But this was… These authors, Dott and Batten, and with their citations, identified three areas around the world that were formed in ancient delta systems like the Amazon Delta today. One of them, the first one I’ve shown in red here, uh, we knew about that one, right?
That’s the Catskill project. That’s where Ted and I were already working and finding fossils. The second one is up in, uh, Greenland.
Uh, this is East Greenland. I already showed you a limbed animal from there. Um, this is well-known.
But there was a third area that stopped me in my tracks, and it’s an area extending about fifteen hundred kilometers east to west across the Canadian Arctic, which was mapped by these guys. It’s said to be, you know, Devonian age rocks, late Devonian age rocks, formed in ancient delta systems, uh, completely unexplored. And that, you know, that literally stopped us.
So we ran to the library, and this all happened in one morning. Ran to the library, and there we started to uncover a really wonderful story, and just indulge me as I spend a second or two on this little story. The story begins in the 1890s in Norway, where the Norwegians want, were, wanted to run to the uh North Pole.
There was a race to get to the North Pole, and the Norwegians had a really bright idea to design a ship, a really strong wooden boat, and that this wooden boat would be sitting in the Canadian- in the, in the Arctic and get carried by currents up to the North Pole. That was their idea, and they had an explorer named Nansen, who was a remarkable individual in many ways, who helped design this boat, and this boat is called the Fram, which means forward in Norwegian, and it’s truly a remarkable ship. This is a boat that took Nansen’s furthest north.
Didn’t get him to the North Pole, but got him close in the, like, eighteen nineties. Um, it, it was eventually to take Amundsen to the South Pole in around nineteen ten. He also went from north to south.
In the interim, it went to the Canadian Arctic with this crew, and this is the crew led by Otto Sverdrup. He doesn’t look like he’s a very, um, funny guy.
(laughs)
But you know, what they did was for three or four years, they went up to the Canadian Arctic, overwintered there on this ship, the sole purpose being to understand the flora, the fauna, and the rocks of the Canadian Arctic. On the boat was this gentleman here, Per Schei, and he’s the hero of the story. Um, so what they did was they went to southern Ellesmere Island, uh, from eight- nine- 1898 to 1902.
And they went to these fjords, uh, down here, overwintering, and it’s a pretty harsh place to overwinter, I could tell you that much. Um, and Schei would get off the boat and start mapping the geology. This is Per Schei.
Um, he’d start mapping the geology, and you could see, uh, he… Here’s a fjord he went to called Goose Fjord, and he started mapping it out, and he started to pull out, uh, bones of fish, and these were the species of fish, the faunal list, that he, um, that he brought about. Pieces, right?
You know, flecks and this and that. This was actually to be lost. No one really was to cite this.
Uh, uh, Per Schei, um, passed away tragically after the return of the Fram. I- he died at age thirty. Um, and this work was subsequently just picked up by a guy named Kiær in 1915, who described it, and then this paper sort of sat in the literature, never really, never really cited.
Until nineteen seventy-four, this gentleman comes along, Ashton Embry, who, um, mapped– who was part of responsible for running a mapping project in the Canadian Arctic, mapping the rocks of the Arctic for a variety of economic reasons. And what Ashton did is a map in the Arctic, he really did a precise map, which basically told us that we had to work there and where we had to work. And, uh, the paper that did it is this, uh, and it was published in 1976.
And the reason why I’m showing you this paper is there was a single page in the paper that basically told us we had to go immediately to the Canadian Arctic. And this is the page. It doesn’t look like much, a lot of words in the page, but I’ll blow up two areas for you where he talks about age.
Blow it up. It says, “The available data indicate an age of early to middle Frasnian.” You remember the question mark I showed you before?
That’s the question mark. Then it really where, uh, we lost it
(laughter)
was essentially when we saw what he described as the Fram Formation. The Fram Formation is similar to the Catskill Formation of Pennsylvania. So here we had rocks at the question mark that were similar to the Catskill Formation of Pennsylvania. This all happened in the morning in 1998 in, um,
(laughter)
you know, in, uh, in, uh, my office in the library at the University of Pennsylvania. We were shaking. There was nothing else we could do.
We went to get some Chinese food. So, um, we went, uh, for Chinese food. I had my Kung Pao chicken, and this really sealed the deal.
I opened my fortune cookie, and it- and it, and it said, “Soon you will be at the top of the world.”
(laughter)
(gasp)
So I was like, “Okay, we’re outta here.” Anyway, so that was, uh, that’s, uh, got us there. So, um, so this is what…
Uh, so we’re dealing with Nunavut Territory. Here’s the North Pole. Uh, we’re 600 miles or 700 miles from the North Pole.
Um, this is Ellesmere Island right here. Here’s Ellesmere. This is what Ashton maps as the e- exposures of the, um, of the Devonian, the Canadian Arctic.
He named the key formation, the one that’s most like the Catskill formation, after that boat, the Fram, and it’s called the Fram Formation right here. So it’s, it’s actually right at that right age, the question mark. The earliest known tetrapods, limbed animals at the time, were from up here, so we’re significantly earlier in time.
And again, just to show you the cartoon, he mapped it as a delta system with a series of highlands to the east and north, an inland sea to the west, and a series of streams and rivers draining from east to west. So off we go. Well, it’s a little bit of a challenge because the place is, uh, up there, right?
It’s not here where I could drive with my Subaru to, you know, Pennsylvania. It’s up here, um, which creates problems, I mean, logistic problems. Um, so the nearest town to us where we end up working is a couple hundred miles away, and this is a picture of that town with a population of about a hundred and seventy people, um, in spring.
It’s Grise Fiord, um, Grise Fiord in Nunavut. It’s not, you know, not a hotbed of activity. Um, so it’s quite remote, you know, so every-everything we bring is, is fairly precious.
We bring a small crew, as I’ll show you in a second. And we, because we get around through this ferry operation of helicopters and planes. Since we’re so, we’re farther than a tank of gas could take us in a helicopter, so fuel has to be ferried in to get us, uh, to where we wanna go.
So we take these planes which land actually on the rock and tundra here. It’s pretty, um, thrilling actually. And then if you define that term loosely, and and then the helicopters take us into our camps.
Because that, it really affects the science we can do. We can’t bring big crews. And importantly, um, when we find something and, i.e. fossils, which are very heavy, we can’t bring a lot of them back.
And so we leave a lot of what we find out there and we, you know, it’s, it’s a real decision. We’re out there for five or six weeks, and we’re making, uh, sort of hard choices about what stays, uh, and what comes with us. So we started in 1999.
The fortune cookie was in 1998. It took us about a year to raise money, and so we, uh, went to the western part of the Arctic first. This is what camp looks like.
Personal tents, main tent. What we do is, basically, these are the Devonian rocks, and since you have this freeze thaw in the Arctic, the, um, bones come weathering out quite nicely. Um, and, you know, we walk over the rocks, and when you find bones, you look for the layers that they’re coming from.
Um, in 1999, we didn’t find much. We had terrible weather. And it turns out we were actually in a much deeper ocean, ancient, deeper ocean than we wanted to be.
So following the delta model, we had to move upstream. And what that meant geologically is moving east. And when we moved east to southern Ellesmere Island here, that’s when we started to find, um, lobe-finned fish in abundance.
Um, bits and pieces of them at least, along these sort of cliff things as we w– up– walk up and down the cliffs. The, um, big discovery was made by a college undergraduate, Jason Downs, who joined us, uh, one year to sort of apprentice. Uh, this is, uh, the site Jason was to discover in the morning, uh, before he discovered it.
So a-about three hours later– Ted took this picture, about three hours later, Jason was to walk over this little patch here. I don’t know if you can see it. It’s sort of a, uh, a greenish gray patch.
We didn’t know it at the time, but Jason had discovered an enormous quantity of bone. Um, he was late back to camp. It was actually quite a worry.
But he returned to camp with pile after pile of bone. So what we did that night was, since it’s daylight 24 hours a day in the Arctic, this is us that night around midnight or 1:00 in the morning, actually crawling at Jason’s site, um, to find the layer that Jason’s bones were coming from. Now this grayish-green carpet here was formed as, I mean, should say a carpet of thousands and thousands and thousands of fish bones of which you’re seeing like lungfish tooth plates and things like that here.
It took us about a year, I should say, to f– I mean, a whole year to actually find that layer. It was actually quite hard.
But when we found it, we, uh, were able to isolate it. This is Ted here and the crew. Um, the, uh, uh, the layer was exposed, uh, as a series of, of, of s-fish skeletons buried one on top of the other.
So Jason’s little carpet of fish fragments was formed by skeletons. Mostly, you know, half skeletons, occasionally a full skeleton, but it was really articulated material that was coming out. So we opened up the hole fairly large.
This is what it looked like, um, uh, in two thousand six, actually, after a while. And the big discovery happened here with, uh, my colleague Steve Gatesy, who was cracking rock and discovered this. I don’t know if you’re going to see it, but you see Devonian– you see the Devonian rock here.
See this little V? And there’s a little slash there. This little V. He said, “Hey, guys, what’s this?”
We looked at it. It turns out it’s a snout of a fish. And not just any fish, a flat-headed fish.
You can tell it’s a flat-headed snout. So remember I showed you before, conical head, flat head? Here had a flat head sticking out of the cliff looking me in the eye.
Right? So I kinda knew we found what we were looking for. And so what it became then was to remove these things very carefully.
As we removed this one, we found about four more of these flat-headed fish. We now have about twenty of them in various states, you know, some ind- from individual bones to whole skeletons. To the skeletons, we have about five.
So they come home on the bottom of a helicopter, and they so when these came back, it was in the fall of two thousand and five. The preparators take over, and these are people who work with a needle and pin, and, uh, these things come back encased in plaster. And this is Steve’s specimen.
They sit for months at a time. This took several months. Uh, Fred Mullison in Philadelphia did this.
Removing the rock grain by grain, and here you can see after a-a-about six or seven weeks, um, a top of a head was revealed. This is one orbit where an eye would be. This is another orbit where an eye would be.
It looks like you’re dealing with the top of a flat head. A few more months go by, and this was started to be exposed. Here’s the head showing itself.
Here’s one orbit, here’s the other. This is a shoulder, and this is a shoulder. Um, it looks like we have a neck with no connection of bone to the shoulder.
Um, this thing got really interesting. As this was happening, a trial was going on in Pennsylvania, the Dover trial, um, Kitzmiller case, where intelligent design, uh, I mean, this– And some people were saying during that trial, uh, that whether, that there were no transitional, uh, fossils with transitional features in the fossil record.
And here, sitting on our desks, both in Chicago and Philadelphia, were these things exposing themselves. So as we began to prepare it, you know, here’s a fish from about three hundred and eighty million years ago. Here’s an early limbed animal from about three hundred and sixty-five million years ago.
Here’s the new fish. I use that term for lack of a better word. Um, what it is, we have the extend in size from about a foot and a half long to nine feet long.
The creature here is four feet long. I’m only showing you the front half. You can see it has scales in its back.
These have been squashed in. Scales in its back and a fin, fins with fin webbing. Um, yet it has a flattish head with eyes on top.
It has a real neck. This is, uh, it’s lacking an operculum, which most, uh, fish have. Um, so it has a mosaic of features of both fish and land-living creatures.
Um, so you see it as a mosaic, like a lobe-fin fish, it has fins and scales and primitive jaws. Like a land-living animal, it has a neck, wrists, flat head, and expanded ribs. So here we have a wonderful fossil with transitional features, of limbs, of heads, and so forth.
So, um, being the discoverers of this creature, we got to name it, and so we wanted the name to reflect to its Inuit heritage. We worked there with the permission of the Inuit government, um, and Inuit elders. They were very helpful to us, and we wanted the name to reflect its, its provenance.
And so we had a naming project where we engaged the Nunavut elders, these are the Nunavut elders here, uh, to come up with a name to meet two criteria. Uh, criterion number one was a name that was meaningful to them and to us, and number two was a name that we could pronounce. Uh, and this is the name of the committee, so the second very-
It didn’t lend a lot of confidence that we have a name we could pronounce. Anyway, so, um, I talked to one of these people, I believe it’s this guy here, I’m not totally sure. But we were talking on the phone over about a month trying to describe what it was, and you know, I’d said, “Well, you know, we have a fish, and it comes in rock.”
You know, long pause. “Well, no, hunters don’t find fish in rocks, they’re in streams or ocean.” Like, “No, no, no, it’s a fossil” and it… there were so many gaps in the way to communicate here.
There they had no concept for fossil and so forth. So eventually, one conversation I’ll never forget, he said, “You know, just what is it? Tell me what it is and where it lived.”
I said, “Oh, it’s a, it’s a large freshwater fish.” He says, “Why didn’t you say so?” “You have yourself a Tiktaalik.”
I said, “A Tiktaalik?” “What’s that?” He says, “It’s a large” freshwater fish in our language.”
So that was the, um, that was how, how the name stuck. But anyway, back to the sci- to the biology here. The, um…
So we had several of these things, and what we were very fortunate to have several specimens because that means we can now take them apart to begin to understand how did the bones work, how did the joints work, how does… And then put the animal together again to figure out how it compares to creatures along the evolutionary tree, and how does it tell us about how this great transformation happened. And this is what it’s all about.
And so here you’re looking at one of our large specimens, about nine feet long. And you see a, um… Here’s a lower jaw.
Here’s another lower jaw. So you’re looking at it like this, the two jaws like yay. Um, and it was once specimens like these that we started to take limb bones apart.
So we found here’s an upper arm bone, a humerus,
(coughs)
excuse me, that we pared out, and here’s a shoulder. And so we took all these things out, and we were really fortunate in that not only did we have many of the bones of the l– of the fin, so you take off the fin webbing, this thing had fin webbing, and then you see, just like our arm, if you were to look at your own arm in the skeleton, you have one bone, upper arm bone, two bones in the forearm, a series of joints here that as they go distally, they can flex and extend, and they, those joints go all the way out to your fingers. And that’s essentially what you have here.
One bone, two bones. You have a series of joints that are capable of flexion, just like, like your wrists and fingers. And indeed, we can compare these bones, this bone here and this bone here, to bones that are actually in, uh, amphibians, creatures for lack of a better word.
Um, and we can compare them u- up and down the, the phyla- the evolutionary tree. What got really interesting is when we took the bones apart, we were able to take each joint apart. So what we did was we took the shoulder apart, and here’s the shoulder of Tiktaalik.
Here’s the socket on the shoulder, here’s the ball on the humerus. And we can see that from the detailed shape what the likely and unlikely patterns of kinematics, of motion of one bone on the other, would be at the shoulder. Very unusual shoulder in some ways.
It has a ball, but it has a sort of cam stop here, which would prevent it from this action of protraction. We could see the elbow of Tiktaalik. Here’s the r– here’s the radius, and here’s the ulna, and you can see the sockets where they’d fit on the elbow joint of the distal humerus.
This is the arm bone, and you see where they’d fit on. And you can see how this one facet would sort of rotates this, this, this, down this side here. That means this bone could rotate far down into the plane of the, the slide.
That’s important, as I’ll show you later. And then we can do it for every other joint in the thing. It was really remarkable to be able to do that, and what we’re doing now is actually modeling it, uh, digitally to see how these bones would move on one another.
But to give you a sense of all this, let’s just look at the shoulder. And I’m gonna, I have three, uh, creatures here. I have one, a lobe-finned fish.
This is a Eusthenopteron. Here’s an early limbed animal, Acanthostega, and you’re seeing the shoulders here from, from the side. Okay, so you’re, like, looking at the animal from the side like this.
And here’s Tiktaalik. One of the things is you can see the shoulder socket here in Acanthostega, and you can’t see it in Eusthenopteron. Well, if you pop on the humerus, you can see the upper arm bone, you can see what that means.
The, in Acanthostega, this early limbed animal, the humerus or upper arm bone is coming out at you like this, like a crocodile. So the arm, the, the limb is held to the side of the body. Whereas in fish, like the, uh, like Eusthenopteron, the, um, the humerus is facing backwards like this.
In Tiktaalik, it’s different. It’s rotated, that whole joint is rotated, so it’s sort of intermediate in position between the bone that faces to the side and Acanthostega and backwards, uh, in Eusthenopteron. Then you just add the other bones in.
If you add the forearm bones, the radius and ulna, it turns out that the radius and ulna in Tiktaalik, just like Acanthostega, are capable of flexion, like yay. And indeed, the radius can rotate inwards in what we call a motion called pronation, like moving your thumb, uh, inwards. And when you add the other bones in, we can begin to see what Tiktaalik was able to do.
Tiktaalik is specialized to do a form of a push-up, With elbow bent and wrist extended, with a small set of palm-ish bones, it can… And remember, the fin webbing is sticking out here as well, um, you can support the body in a form of a push-up with a, a palm equivalent, uh, flush against the ground. What was nice about these specimens, too, and something we haven’t really published yet, is the notion that we can begin to see how the fin webbing changes during this, uh, during this change.
So you’re looking at the, the type specimen, one of the better specimens of Tiktaalik from the top. And here you see the fin with its fin webbing. We have several of these specimens that are intact, which show the relationship between the limb bones I just showed you and the fin webbing.
And that’s really important because if you look at a fish like Eusthenopteron and Acanthostega, you see the big shift in the fin webbing. They lose it. Fish have fin webbing, limbed animals do not.
If you look at Tiktaalik, it’s reduced the fin webbing, but it’s done so in a very important way. It’s done so not from the outside in, but from the inside out. It’s done it over the joints.
So where it’s lost the fin webbing in these big rods is over the elbow joint and over the wrist joint, which totally makes sense. Those are the areas where the, the, um, the, the fin, uh, would bend. So this is, uh, sort of more or less what we think, uh, the– what the fin of Tiktaalik was able to do, function like a paddle or like a, a, a, a prop, uh, to enabling the creature to do a pushup.
Uh, this is the reconstruction of Tiktaalik as it was in two thousand and six. It has a flat head with eyes on top, a pair of nostrils. It has a neck where the head is separate from the shoulder, and key in this is the loss of many bones, including the opercular bone, which is the bone that– on a ser– a whole series of opercular bones.
It has a fin webbing, and inside that fin webbing is an upper arm bones, uh, uh, forearm bones, the equivalents, and both proximal carpal and distal carpal bones. That is the, the, the equivalents of a wrist. Big expanded ribs.
We now know a lot about the hind fin with the pelvis and so forth. We’re lacking the, the femur. So that’s why I haven’t drawn it in yet.
One of the key things here is really understanding Tiktaalik as a living animal, because then we can begin to see this transformation, and that’s what– where I wanna get to. One of the things about Tiktaalik is if it’s supporting itself as the appendages suggest on the ground, like in a pushup, that’s when the neck becomes, becomes quite handy. If you look at a, a fish, it has a head fused to the shoulder, and it does so by a series of bones at the back of the skull and a series of opercular bones, a whole opercular series that connect the cheek to the shoulder.
These bones, I should say, the opercular bones, have several functions. They actually connect the, the head to the shoulder, but they function in breathing in fish as well. They, they’re pumps that draw water across the gills.
One of the big changes in the transition to tetrapods, to limbed animals, is the loss of all these bones. So not only do you have a neck, but you’ve lost the operculum as well. And it turns out Tiktaalik is much the same.
It’s evolved the ability to do push-ups, and at the same time it’s lost this whole series of bones here. And what this shows is, with this opercular series, is how one change, loss of simple bones, can affect several traits of the creature. From head mobility, which is important for locomotion and, and a variety of behaviors it has, to breathing as well.
Because as you lose the operculum, there are new ways that have to come about to bring water through the, through the mouth. So what’s Tiktaalik specialized to do? Um, here’s the, uh, reconstruction.
It’s a, it’s a benthic animal, able to live on the water bottoms with a flat head with eyes on top, looking at prey as they go by. It’s also an animal that’s able to live at the margin of, of water and land, um, and to feed– it’s a carnivore, to feed either on fish or on the large variety of invertebrates that are present o-on land and in the air at this time, uh, as well. So, um, if you look at the family tree, if you plot all the various characters that we can do, Tiktaalik turns out to be very closely related, uh, to limbed animals.
And so no surprise given all the features that we found. Now to really make sense of this, and to get back to the whole point of the talk, which is really understanding great transformations. You remember I opened up the fact that this is an integrative discipline.
This is something we have to pull in data from many different lines of inquiry. It really comes down, we have to think of ways to integrate these studies of fossils. And I should say right off the bat that Tiktaalik gains– its only gains meaning in relationship to the other fossils that we have in this sequence, in this series here.
Okay? It alone doesn’t tell us anything. It’s this whole batch of things which tell us how this transition happened.
But we really have to begin to think about what living fish can tell us, and how that can– what lessons can we learn from them about how fish evolved to, to, to walk on land and to live on land. And there’s a couple things. I’m just gonna isolate three.
One is we can study their genes and genetics. That is, we can look at the genetic recipe that builds the bodies of fish and builds the bodies of land-living animals, and we can ask the question, what’s different among them? And we can do that at the level of organs, we can do that at the level of tissues, we can do that at a variety of different levels with increasing precision every year.
We can look at appendage support, how do fish support themselves with their appendage? What are the models of living organisms that do this kind of thing today? And we can look at air breathing.
How does air breathing happen in fish? And, you know, we could do with… This is arbitrary, I could add in another four or five things on here, but I wanted to give you some, some take-home messages about what we can learn from living fish.
Well, if you look at it, um, what I’m gonna show you here is, what you can see are limbs. These are fins up here and limbs down here. If you take living creatures alone with no fossils, we have limbs with one bone, two bones, little bones and fingers, and I’m showing you a chicken and a human, and they have a one bone, two bone sort of finger arrangement as well, despite the fact that it’s in a fin.
And if you compare it to fish fins that are alive today, they don’t look a whole lot alike. Here’s a lungfish here, a creature Neoceratodus from, uh, from, uh, Australia, and it has one bone, okay, down here, but it doesn’t have any other bones that look very limb-like. Neither do any of these other fins here.
Where the comparison gains meaning are when we add the fossils to this evolutionary tree, that we begin to see this one bone, two bone, uh, uh, limb pattern appearing and evolving in our own lineage. So if you just take living creatures, this transition from fin, I’m sorry, from fin to limb looks vast. But when you start to add in the fossil taxa, the fossil creatures and species, you begin to see the links between them.
But really where it’s important is we can study the genetics and developmental biology of living creatures in a way that we can’t do with, uh, with the ones that have been dead for three hundred and seventy-five million years. And when we do that, what we can begin to understand is the genetic toolkit and the recipe that builds the skeleton of an appendage. We can begin to ask the question is what are the set of genetic interactions that build the pattern of one bone, two bones, little bones, fingers?
We begin to ask the question, what’s the genetic recipe that controls the number of bones in different parts of the body, this size and shape, and so forth? And if we do that, we can begin to see– And if– by about the late nineties, we began to see that there’s a very characteristic set of patterns of gene activity and gene function, Genes called the Hox genes and others, I’m not gonna go through them all, um, that characterize the development of limbs.
It’s a cascade of events, of cellular events and genetic events, uh, that produce the pattern of limbs. I’m gonna talk about that more tomorrow. However, what was really interesting is we knew what this stuff was– how it was happening in chickens and mice and frogs.
The real surprise came when we started to look at these genetic interactions and processes acting in fish fins. And what was truly remarkable is that many of the genetic processes that build the fins, the skeleton of the fins of fish, and indeed that pattern them, are very similar to those that pattern, um, the, the limbs of, of, of, of limbed animals. And in fact, it’s very clear that, you know, if you were to ask the question, um, are there any new genes that are patterning the limbs of, of limbed animals that aren’t present in fins?
The answer is likely no. That is, it’s not like the origin of limbs involved, necessarily involved the origin of whole new sets of genes. It involved whole new sets of genetic interactions and new ways of genes being turned on and off in new places, and so forth.
So it’s using existing genes in new ways and reconfiguring them. So the genetic, if you will, the toolkit that’s necessary to build appendages was already present when a lot of these fossils hit the scene. So the the the repertoire was already there.
If we look at appendage support in extant creatures, what you’ll find is a lot of fish actually support themselves with their appendages. Most, uh, famous among this is the mudskipper. Mudskippers can live on land for a period of time, about twenty-four hours, at the max, in the mud, and they have appendages with a little type of, of elbow.
And if you look at frogfishes, a frogfish is a creature that can walk on, uh, on, uh, in the water. This is actually an aquatic creature that can walk around. It even has a little sort of elbow and a distal paddle.
What’s remarkable about all these creatures that have evolved to sort of walk or support themselves with their appendages, is oftentimes they do it with equivalent kinds of joints, shoulders and, and paddles and so forth. But in each case that they do it, they do it with different bones. So here is the frogfish fin.
And you remember, we have this one bone, two bone, little bone ray pattern. This is nothing like that. This is three bones, a big old plate, a big old rod, a big old rod here, and a bunch of spikes coming off.
That’s very different from the limb pattern in early– in limbed animals. So what you see is when fish that are distantly related to Tiktaalik and, and other creatures evolve appendage support, they evolve similar kinds of joints, but they do it with different sets of bones. Only one lineage did it our way, and that’s the Tiktaalik lobe-finned fish, uh, lineage.
Finally, you can ask the question, well, you know, the creatures that, you know, doing appendage support and walking in mud and so forth, how do they breathe? Well, if you look at the evolutionary tree of fish, and you ask the question, how many of these things are air breathers? There are about thirty thousand different species of fish, say twenty-nine thousand of them or so.
Of those that are looked at so far, in the last major monograph, somebody identified, uh, three hundred and seventy-five species of air-breathing fish, which is what’s been looked at. There are certainly a whole lot more. In forty-nine different families, and if you map it to a tree, it evolved at least twenty-four times.
That likely is about three times too low based on if you look at the trees that it was mapped on. So air-breathing in fish has evolved many times independently in living extant fish. And how do they do it?
The most common way that fish breathe air, uh, at least in the, in the, in, in the evolutionary tree, is they use lungs. In fact, lungs are primitive. Lungs are primitive to this thing here, a Polypterus, to lungfish.
Indeed, if you look at Tiktaalik and where it fits on this tree, Tiktaalik’s right about here. So lungs hit the scene well before Tiktaalik and even its distant relatives, uh, were around in Devonian streams. They evolve in these cases, in each case, like in the lungfish, they evolve to allow creatures to breathe when water gets anoxic and oxygen poor.
They go up and gulp air in many different ways. And there are other, I mean, examples as well. There are diverse air-breathing organs in this group here, which is very speciose.
Some of these creatures, um, vascularize their swim bladders, they vascularize their mouths. There are numerous strategies for air breathing in fish, but lungs are the ones that are actually primitive to our own lineage. So returning to the initial sort of challenge, um, with air breathing evolving multiple times independently, uh, in fish, with the genes necessary to build limbs already present in fish fins, with appendage support appearing in numerous kinds of fish independently, with intermediates in the fossil record at just the right time in the fossil record, you, you know, don’t ask the question, how could this transition ever have happened?
Ask the question, why did it happen only once? Um, it’s so– This barrier between water and land seems to be very porous, at least for creatures that are specializing for the interface between water and land. And why did it evolve only once?
I can only speculate. In our lineage, it only evolved once. Um, perhaps it’s some sort of ecological king of the hill situation where, you know, you have an incumbent who–
And it, it sort of displaces any, uh, any other lineages that would evolve to walk on land because there’s already an incumbent set of species, uh, there. So all this is in terms of it’s extrapolating to great transformations. You know, one of– one way of thinking about great transformations is the popular one you see day to day in cartoons and oftentimes in texts, which is as a ladder-like notion of change.
That is, you know, one species leads to another species, leads to another species. That’s not how it works. That’s not how the water-to-land transition works.
That’s not how any of the other great transitions works. It’s not like Tiktaalik and its k- its, its kin were sitting around thinking, “Oh, golly, I want to evolve lungs So I can walk on land.
I want to evolve wrists to walk on land.” It was adaptation to life in water. It was diversification in life in water, finding new strategies to live on the water bottom, in the shallows, in the interface between water and land, on the mudflats and so forth, that led to the diverse adaptations which became useful when the need came to walk on land.
And so what we think about is evolution not as this ladder, but as Darwin originally proposed, as a tree, as a tree of evolution with a diverse set of strategies e-evolving. And I should say that there is a unifying theme to many of the great transformations. I’m going to just close with a series of these.
Um, you can think of the transformation from something like, you know, the common ancestor of an acorn worm and the earliest fish with a skull. If you look at this change, if you look at creatures both living and long dead, what you’d find is a wonderful series of creat-creatures with transitional, uh, features, uh, between, uh, acorn worm and, a-and fish. And I should say, some of the most important, um, species in this transformation Have j– been discovered in the last thirty years.
You could say the same thing with any other great tran-transformation. Take whales from a, uh, take whales and their derivation from a m– four-legged creatures about fifty million years ago. You could find fossils that have a series of transitional features leading to whales.
Devi-devise a family tree well supported by characteristics which show how this sequence of changes happened. And again, the major fossils that support this transformation, discovered in the last twenty years. And the same thing is true with the shift from reptiles, uh, to mammals, uh, th-to the evolution of our own species, Homo sapiens, from our primate relatives, from birds to dinosaurs.
When underlying all these transformations is this, that some of the most important fossils in understanding the tran- great transitions in the history of life have been discovered in the last thirty years. And when you think about this field, these are the great times in understanding great transformations. Nowhere has it become easier to find fossils from around the world, to analyze them in new ways with new imaging and new quantitative techniques, to study living creatures with, uh, understanding their genes and genomes and sequencing at an ever-rapid clip, to understand, uh, the, uh, the genes that build bodies and control development, to understand the biomechanics of, of the features that these creatures use to walk and to live.
To understand the ecosystems and the systems that, uh, function as ecosystems, and the food webs, the ways these creatures would have, would have interacted. Nowhere, no– At no other time in the history of our science has it been a better time to study the great transformations, because this is now a fundal-fundamentally integrative field and an integrative biology. Thank you very much.
(applause and cheering)
[00:54:17] WILLIAM LESTER:
Professor Shubin has agreed to respond to questions.
[00:54:24] SPEAKER 1:
Could you kindly come up front? You’ll need to use the microphone so it’s picked up on the cameras, please. And we ask that you make your questions brief if at all possible. Thank you.
[00:54:38] AUDIENCE MEMBER:
Where does the crossopterygian, uh, fit in this, uh-
[00:54:41] NEIL SHUBIN:
So, uh, something like the coelacanth, you’re thinking like Latimeria. Um, the, um… You’re probably thinking of, like, the, the famous missing link that was discovered, um, alive in the deep sea. Um, and on the tree, it’s actually down towards the, um, uh, let’s go ahead.
It’s really pretty low on the tree, lower than Tiktaalik and the other creatures. Let me pop that up for you here. It’s down.
So it’s off this tree. It’s basically, uh, down here, or at the floor. It’s like there’s the lungfish
And then the coelacanth down here. Uh, you have a whole series of fossil creatures that sort of embed here. What’s important about this transformation is the living creatures are great, but they’re actually di- more distantly related to limbed animals than a whole series of fossil creatures, which tell us a lot about the anatomy.
But the coelacanth has a, um, has a, uh, a lung. It’s fat-filled, uh, which, you know, it– which, which is similar to the lungfish and other creatures lower in the tree, so.
[00:55:39] MODERATOR:
There was a question.
[00:55:44] AUDIENCE MEMBER 2:
You mentioned at the outset that your focus was on the the Devonian, and I think the Triassic as well. Uh, could you quickly, uh, describe what you’re looking for in the Triassic?
[00:55:53] NEIL SHUBIN:
Yeah, the Triassic is another case. So one of the the thing that attracted me to the Devonian is it’s the age of fish when the major groups of fish arose. You know, the diversification of sharks and bony fish of a variety of types, including limbed animals.
The Triassic is special because it’s, it contains the earliest appearance of mammals, dinosaurs, turtles, crocodiles, uh, salamanders, frogs, uh, you know, or, or limbless, uh, amphibians. Um, it has, you know, y-when you look at the Triassic, it’s one of those periods where revolution is in the air, in this case, at the level of sort of, uh, extant reptiles and amphibians. You know, the major groups we think of, of reptiles and amphibians.
So what motivated my fieldwork was obviously the desire to find early representatives of each of those groups that tell us something about how those transformations happened. And, you know, much of it was the origin of mammals was really what motivated quite a bit of that. And we were looking mostly at how the mammal ear evolved from jaw bones and reptiles.
[00:56:51] AUDIENCE MEMBER:
Neil, thanks. Uh, I think this slide is a kind of a good starting point for this question, but if you look at the, if you look at the heads of some of these critters and also one of the points that you brought up earlier in your talk, you noticed– you noted that they changed from kind of a round conical head to a flattened head, and I was just gonna ask if, uh, you would mind elaborating on what competing hypotheses might explain that, that flattening of the skull.
[00:57:15] NEIL SHUBIN:
Sure. So if you look at flattening of the skull, actually, when you get to some of these creatures here, to the really big ones, those heads get flat as well. And so if you look at this lineage, and you look at the endpoints and some really giant creatures, they get giant, big, flat old heads.
So ecologically, I mean, flat heads is a variety– I mean, it has a variety of ecological roles. You know, one is obviously in the benthos to look up. One is actually on the margins between water and land, and also biomechanically.
I mean, in terms of biting, having a flat head is very useful for a variety of ways. And so because the way that the palate can support the, the the sides of the jaw is very, is, is very, you know, useful. Also, the lungfish also have flat heads down here.
So flat heads appear in several cases. It’s just on this lineage here, when you look at this kind of flat head, and when I say flat head, I mean with a specific set of proportions from front to back as well, as well as the thickness of the palate, which is, is very thin here. No other creature has a palate that is thin as, say, Tiktaalik and is shared with tetrapods as well, so.
[00:58:09] AUDIENCE MEMBER:
Uh, since you’ve lost the operculum, how does water move over the gills? Any ideas?
[00:58:14] NEIL SHUBIN:
Yeah. Qu– I mean, well, you have a big wide old head, and so what’s happened is a big wide head with these big gular bones that are pumps. So you’re using…
So there are two pumps that draw– that push water acro– we think, push water across the gills. There’s a mouth pump, where you can suck in through the mouth by opening and closing the mouth. So having a wide head in that case is a very useful trait to pump water across the… into the mouth.
Um, and then the, the operculum is a pull, and the, the closure of the mouth is, is a push. So when you lose the operculum, what you’re probably relying more on is the mouth pumping mechanism, both for water breathing and air breathing. That’s the opercular pumping mechanism.
So it seems to be that the width of the head, the expansion of the width of the head, probably took on a whole new sort of functional significance when you lost that operculum, because having a wide head and losing the operculum is such that it enables you to pump more water across the, across the gills, or air into the lungs, as needs be.
[00:59:05] AUDIENCE MEMBER:
Um, why do you think this transition happened? Why didn’t the fish just stay in the sea?
[00:59:09] NEIL SHUBIN:
Yeah, so, um, there, why the transition happened. So there’s, um, a number of competing hypotheses and, and, you know, it’s like, so the– let’s just lay them all out. One is, uh, there’s been– the one original one was that there was climate change, that there was drying, uh, uh, increased aridity around the world that led to smaller ponds, and animals would have to walk between the ponds.
It doesn’t appear to be that there’s much support for that hypothesis anymore. One of the things you can do is compare water and land at this time period. So this just gives you context.
Um, let’s just go to the reconstruction that we did of the, um, Catskill stuff. You know, so more or less, uh, land is actually food rich. You know, there’s quite a bit of invertebrates, uh, arthropods and so forth on land, and, um, and plants have already inhabited land and so forth.
So there’s quite a bit of food on land and very few competitors, in fact, none at this stage. Water is teeming with competitors, uh, teeming with creatures that will immediately eat you. I mean, if you were in a time machine and standing here, you wouldn’t last very long with creatures like Tiktaalik and this, uh, this swimming around.
So, you know, it could be that there’s this, this balance between a competitor rich and predator rich water versus a, a land which is, uh, predator free, uh, competitor more or less free and food rich. So there’s that dichotomy as well. Well, there are other, um, hypotheses out there that relate to changes in the, uh, in the atmosphere from inc- from a, from a drop in, uh, global, uh, oxygen and water in the middle, in the early middle Devonian, uh, to an oxygen high, uh, later in the Devonian and then through the, uh, later in the Carboniferous.
So you’re gonna, so you can sort of separate these hypotheses out in terms of looking at sort of the predation versus competition, but also in terms of, uh, uh, climate change. But they’re all speculation at this point in terms of knowing the mechanism that drove them out.
[01:00:57] AUDIENCE MEMBER:
You said that, uh, Tiktaalik was a freshwater organism. What sort of analogs do you think happened in the marine environment?
[01:01:03] NEIL SHUBIN:
Well, you know, Tiktaalik was freshwater, but, you know, some of these other creatures are found in brackish water. So if you look at the tree, it seems to be these things are actually in the shallows, in the interface between water and land, both in sort of salty water as well as in, um, uh, as in, is in the freshwater. So if you look at some of these creatures here, there are, um, both, uh, sort of quasi-brackish water, uh, ones as well, and this creature here, and there are some marine, uh, creatures along these lines too.
So it’s the saltwater thing is actually a whole, versus freshwater, is a little more complicated than that. I think these things were able to, uh, had, had represented as an evolutionary tree, had representatives in both salt and, uh, and freshwater. And they might have been anadromous, you know, like a salmon in some cases, for all we know.
[01:01:46] WILLIAM LESTER:
Well, I see no one coming forward at this point. So let us, uh, thank our speaker, Professor Neil Shubin, for a wonderful presentation.
(applause)
And remember that he speaks same time, same place tomorrow.
