The Great Transitions in Evolution with Neil Shubin


– [Announcer] This program
is a presentation of UCTV for educational and
noncommercial use only. (gentle music) – Good afternoon, my name is Ellen Gobler. I manage the Graduate Council Lectures, and we’re pleased to have
all of you here today. Thank you so much for joining us. It’s my pleasure to
introduce Andrew Szeri. (audience applauding) – Good afternoon. My name is Andrew Szeri, I’m
Dean of the Graduate Division, and we’re pleased along with
Graduate Council to welcome you to the Charles & Martha
Hitchcock lecture series. Our speaker today is Neil Shubin. The story of how the
endowment came to Berkeley is a nice example of the
ways in which this campus is linked to the history of
California and of the Bay Area. Dr. Charles Hitchcock was
a physician 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, thank you. (audience applauding) – 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 and 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 2004, after scouring the
Canadian Arctic for six years, Shubin and his team unearthed
Tiktaalik roseae crae, a fossil fishapod, which
despite its fishlike 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 350 million years ago. His announcement about the
discovery of this phenomenon on April 6, 2006 in the journal Nature made front page news in
newspapers worldwide. Finding the 375 million year old fossil also spurred Shubin to
write the recent book, Your Inner Fish: A Journey Into The 3.5-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 1982, he earned his PhD from Harvard University in Organsimic and
Evolutionary Biology in 1987, and in 1996 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 at the University of Chicago in 2000. Shubin in currently the Robert R. Bensley Professor of 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
a 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. (audience applauding) – Thank you Dean Szeri, Professor Lester, members of the Hitchcock
Committee, my hosts in the Department 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 the place of
my intellectual roots. Much of what I do is
really sort of flowed from the concepts, ideas, and approaches that I learned during my
time here at Berkeley. So today we’re gonna 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 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. It’s from Press and Siever, a very prominent geology textbook. And what you see is this
linear series is depicted as sort of a corkscrew so
they can fit it on the page. And you see the various
events and the trajectory in the history of our planet, and the history of life on our planet from the presence of the first rocks, the earliest visible life
in the fossil record, the origin of bodies
and plants and animals, and then you see sort of the major events in the history of vertebrate life, creatures with bones, the shift from water to land, 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 or the sort of revolution in the air where there are big things happening. And those time periods have
always attracted my attention for one reason or another. And that’s why I’ve ended up focusing on two time periods in
the history of life, the Triassic and the Devonian, time periods from 200 million years ago and about 375 million years ago. But anyway, I’m gonna show you how this kind of way of
depicting the history and the sequence of events in our world, actually it gets in the way of really understanding and decomposing some of the main events we see
in the history of our planet and life on our planet. And what I’m gonna do is I’m gonna take one particular example, one major transformation, the shift from fish that lives in water to limbed animals 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, an example really of how we can approach all the other transformations
that are out there. So let’s start with the
transformation from water to land. So here what we have the
transformation from water to land. And you see here, I’ve shown a cartoon. This is a complete
caricature of the situation. And if you were to sort
of blue sky this thing, on the back of an envelope, and you know look at a fish, and look at a land living
vertebrate animal with bones, you can sort of say wow
geesh, life in water is vastly different from life on land. Almost every single
system of these creatures had to change. And I just 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. Now just take a few of
them, take respiration, and you have a shift from creatures that are largely water breathing to creatures that are air breathing. This involves whole sweeps
of changes to organs and the ways that organs develop, and circulatory systems,
and lungs and so forth. Feeding, feeding in water is very different from feeding in land. You go from where you have water where you can suck the food into the mouth by changing the volume of the mouth cavity to biting, where on land you can’t suck in unless you’re a Hoover
Dustette or a vacuum cleaner. It’s really more of a biting approach to the capturing and chewing food. Locomotion is completely
different on land from water. I mean, here you have water supported, where you basically have to
support yourself in gravity, it’s not gravity supported, but it’s basically you’re
dealing with gravity as a force. And the skeleton had to change from a water supported to
actually dealing with gravity as a force, on the
ground, on the substrate. And there’s all kinds of other
changes associated with this. Head mobility, you know fish have heads that are largely connected to the body by a series of bones so
when you move the head you move the rest of the body. They don’t have necks whereas land living creatures have necks, their head can move
independently to 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, I don’t see how this
transformation could ever happen. So my sort of goal for the last 20 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 achieve this important shift in evolution. This was sort of the
state of affairs in 1987. This is a textbook written
by one of my predecessors at the University of
Chicago, Len Rodinsky. And I saw this in 1987
in a graduate seminar and it really attracted my interest. ‘Cause what he showed is a
lobe-finned fish on the top. This is a creature from about, the first ones of these appeared about 380 million years ago. And on the bottom you see
an early limbed creature. This is a creature from Greenland, at least that’s what we thought
it looked like at the time, from about 365-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 for features
that have to change.” And to approach this,
it became pretty clear that if we wanted to address this, we had to find new fossils. In fact if we wanted to find new fossils that bridge this gap, we had to find whole new
places to look for fossils. So off we went to start looking for places to find new fossils to 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 fossils. We look for places in the
world that have sort of a convergence of three things. 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 380 to 365 or so million years old. The next thing is you look
for rocks of the right type. Not every kind of rock preserves fossils. Sedimentary rocks preserve fossils better volcanic or metamorphic ones. And indeed within the sedimentary rocks there are certain
depositional environments, environments where those rocks were formed which are more likely
to preserve fossil bone than others for a variety of reason. One because they might reflect
areas where creatures lived. The other is, because they were formed in very gentle environments
with little erosion so that whatever fossils were there were preserved in some detail. The third variable is really important. Actually it’s one of
the most important ones. 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 days, just to find bones weathering out. So it’s really exposures,
rocks of the right age, and rocks of the right type. There’s a third variable when
I stated out on this quest. And that was lack of money. And so I started on my,
this is really true. I started my first academic job after leaving Berkeley as a Miller Fellow, I moved to Philadelphia as
a young assistant professor here in the southeastern
portion of the state. And what I wanted really
was 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 unimportant out of the
state of Pennsylvania and what’s left here is
the Devonian. (laughs) And you can see, I mean it’s
loaded with Devonian Age rocks. And these span an age pretty
much in the late Devonian is the ones I was interested in. And these are rocks about
365 million years old from the Catskill
Formation and they extend into New York and into the
Catskills, hence the name. So it’s pretty clear, from about a three hour
drive from Philadelphia, you know I had access
to Devonian Age rocks. 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 concocted a cartoon really version of what Pennsylvania
was like at this time. If you wanna think what
Pennsylvania was like in the Devonian, get
Pittsburgh, Harrisburg, and Philadelphia out of your
brain and think Amazon Delta. This is really just a cartoon
of the reconstruction. Essentially 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 they’re marine
rocks from this inland sea. And a series a rivers that
drain from east to west. Now if you’re a paleontologist interested in the transition from fish to limbed animal, and you wanna find
fossils along those lines, this is perfect. Because you can sample if you’re lucky, ancient seas, ancient estuaries, all the way up the stream if you’re lucky. I was also lucky in this regard because a graduate student
started working with me. 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. But Ted and I have been working ever since and Ted really has been a
major, major, major part of much of the work, fossil
work, you’re gonna hear about. But Pennsylvania has a problem, I mean it has two of these variables, it has rocks the right age
and rocks of the right type, but unfortunately it’s not
renowned for its exposures. Pennsylvania’s 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, or
where there are streams, but it’s actually the road cuts that were kind of a critical thing. What happens is, you know
Penn DOT will come through and you know when they want to put a road or a bend in a road or widen a road, what would they do, they’d
blow it up, they blow up rock. When they blow up rock,
if we were really lucky, they’d blow up rock in the Devonian. And if you’re super really lucky, they’d blow up rock in
you know the right part of the delta system of the Devonian rocks. And to his was one area
which was widened in the 70s. It’s a road about an hour north of State College, Pennsylvania. It’s a road cut called,
don’t be surprised, Red Hill, ’cause it’s a red hill. A large road cut and when
it was widened in the 70s, it exposed a series of
the strata, the beds here which you can see going up. This is really a fluvial
river environment. And what you see as you walk through here are 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 even part of, and some meandering
streams within this area. So it’s a really rich area. And you see the scale here. There’s a car and there’s
a human being for scale. What is actually 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 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 hills here. We started to find jaws
to these creatures. This is Ted holding one
of our first jaws we found out of this thing. It was just the front end of the jaw. These jaws are like long as your arm and you know with teeth
the size of your thumb. So these are really big monstrous fish that are about 16 feet
long, up to 16 feet long. So large carnivorous fish
coming out of the rocks here. We have lots of other kinds
of fish, invertebrate animals. This is the sidewall of a fish,
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, the humerus, and we started to find a femur, which is an upper leg bone. We found other bones of
the skull and so forth. And this humerus is particularly important because it was very similar
to a humerus known from a Devonian limbed animal from Greenland. The 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 describing the plants. Some of the earliest known forests, with trees, we found their
leaves and trunks and so forth. Land was loaded with lots of life, scorpion-like and spider-like creatures, and many of those from these sites, and then tons of fish from within here. And this is what this road cut, Red Hill road cut in
Pennsylvania looked like when we reconstructed it
with National Geographic. You know you got 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 had these limbed animals 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 are about
365 million years old. And what we were picking up at this point were mostly really well formed tetrapods. 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 to move back in time. Because to move back in time, we begin to understand
some of the transition here and I just want to run through some of the anatomy that’s different. And here you see the
lobe-finned fish on top, which we knew was closely
related to limbed animals. And just look at the head. You see basic differences in
the architecture of the head. You know here at the top you see, you know these creatures
have like a conical head with eyes on either side. The early limbed animals have got almost like a crocodilian kind of head. It’s a flat head with eyes on top. And the architecture of the bones in here actually is somewhat different than 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 and the head is not independent movable, whereas in early limbed animals, like all their descendants, you and I, have a neck with a head that’s
separate from the shoulder and there’s a series of joints
at the base of the skull. And you know finally, and I
can make a long list here, the thing that was
really interesting to me was to understand the
shift from fins to limbs. Fish had 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. These are the fish that are successfully mostly related to them. If we wanted to make any headway, we had to find creatures that were sort of more on this branch, which would really be able to very clearly tell us the sequence of keys or the origin of key features that led to the origin of limbed animals. And to do that, when we look at the age of these things, these things, many of these first appear back around 380, 390 million years ago. Some of them continue all the way up. The earliest limbed animals, tetrapods, appeared around 363,
365 million years ago, the good scalable material. At the time, that’s what we knew. But there is a big gap in our knowledge. We didn’t have many faunas
or floras at this age really here about 375 million years ago. So we had to move back in time. And so we began our hunt again right. So you look, remember we
look for rocks the right age, rocks the right type and exposures. And going through it,
it became pretty clear we had to, we were thinking
about going to Brazil, we were thinking about
working in Colorado. Everything changed for us one
day in the winter of 1998, in my office at the
University Of Pennsylvania. Ted and I were having an argument and to settle the argument, I pulled out a college undergraduate
geology textbook. (laughs) This is I think, the one that
I had was the second edition of Dott and Batten,
Evolution Of The Earth. I believed it was pre-plate
tectonic when it was written. This book is now I think
in the 11th edition or something like that. We settled the debate and as I was thumbing through the book, after that little set to, I came upon this figure in the
textbook in like chapter 14. And it stopped me in my tracks and basically defined my research, at least in the field
for the next six years. So I want to spend a
second on this diagram, it’s that important. It says, Upper Devonian
Sedimentary Facies. Which means, you know rocks
more of less the right age and you know 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. The rocks there were formed,
the Devonian at least, were formed in the ancient ocean. But these authors, Dott and Batten, 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 showed and right here, we know 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 Greenland, this is East Greenland, I already showed you a
limbed animal form there. This is well known. But there’s a third area
that stopped me in my tracks, and it’s an area extending
about 1500 kilometers east to west across the Canadian Arctic, which was mapped by
these guys and said to be Devonian Age rocks,
like Devonian Age rocks, formed in ancient delta systems, completely unexplored. And that, you know, that
literally stopped us. So we ran to the library, and
this all happened 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 1890s in Norway where the Norwegians wanted
to run to the North Pole. There’s 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 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’s called the Fram, which means forward in Norwegian, and it’s truly a remarkable ship. This is a boat that took
Nansen furthest North, it didn’t get him to the North Pole but it got him close in the 1890s, it was eventually to take Amundsen to the South Pole around 1910, so it 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 funny guy, but you know what they did was for three or four years, they went up to the Canadian Arctic overwintered there on the 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, he’s the hero of the story. So what they did was, they went to Southern Ellesmere Island, from 1898 to 1902. And they went to these fjords
down here overwintering, and it’s a pretty harsh
place to overwinter, I can tell you that much. And Schei would get off the boat and start mapping the geology. This is Per Schei. He started mapping the
geology and you can see, here’s a fjord he went
to called Goose Fjord, and he started mapping it out and he started to pull out bones of fish. And these were the species of fish, the fauna list that he brought about. Little pieces, rhino
flex and this and that. This was actually to be lost. No one really was to cite this. Per Schei passed away tragically after the return of the Fram, he died at age 30. And this work was
subsequently just picked up by a guy named Keran in 1915, who described it and then this paper sort of sat in the literature, never really, never
really cited until 1974. This gentleman comes along, Ashton Embry, who mapped, who was partly
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 the paper that did it is this, and it was published in 1976. And the reason why I’m
showing you this paper is there’s 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 on 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 Frannian. You remember the question
mark I showed you before, that’s the question mark. Then it really, where we lost it, (laughs) 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 you know, in my office in a 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 for Chinese food, I had my kung pao chicken, and this really sealed the deal. I opened my fortune cookie, and it said, soon you will be at the top of the world. (laughing) So I was like, okay we’re out of here. Anyway so that got us there. So um, so this is what, so we’re dealing with Nunavut territory, here’s the North Pole, we’re 600 miles or 700
miles from the North Pole, this is Ellesmere Island
right here, here’s Ellesmere. This is what Ashton maps
as the exposures of the, 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 actually right at that right edge, 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, and Inland Sea to the west, and the series of streams and rivers draining from east to west, so off we go. It was a little bit of challenge because the places up there right, it’s not here where I could
drive with my Subaru to, you know Pennsylvania, it’s up here which creates problems, I mean logistic problems. So the nearest town to us
where we ended up working, is a couple hundred miles away, and this is a picture of that town, with a population of about
170 people in spring. It’s Grise Fjord, Grise Fjord, Nunavut. It’s not, you know, not
a hotbed of activity. So it’s quite remote you know, so everything we bring is fairly precious, we bring a small crew as
I’ll show you in a second, 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 to where we want to go. So we take these planes
which land actually on the rock and Tundra here, it’s pretty thrilling actually, and then, if you define that term loosely, and then the helicopters
take us into our camps. Because of that it really
affects the science we can do, we can’t bring big crews and importantly, when we find something, and ie 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 a real decision. We’re out there for five or six weeks, and we’re making sort of,
hard choices about what stays and what comes with us. So we started in 1990, the
fortune cookie was in 1998, it took us about a year to raise money, and so we went to the western
part of the Arctic first, this is what camp looks like, it’s the 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 bones come weathering
out, quite nicely. And you know we walk over the rocks, and when you find bones, you look for the layers
that they’re coming from. In 1999 we didn’t find much,
we had terrible weather, and it turns out we were
actually in 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 lobe-finned in abundance, bits and pieces of them at least, along these sort of cliff things, as we walk up and down the cliffs. The big discovery was made by a college undergraduate Jason Downes, who joined us one year
to sort of apprentice. This is the site Jason was to discover in the morning before he discovered it. So 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 greenish gray patch. We didn’t know it at the time, but Jason had discovered, an enormous quantity of bone. 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 Jason’s site, to find the layer that Jason’s
bones were coming from. Now this grayish green
carpet here was formed, I mean I 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, I mean a whole year, to actually find that layer,
it was actually quite hard, but when we found it, we
were able to isolate it, this is Ted here and the crew, the layer was exposed as
a series of 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, and this is what it looked like in 2006 actually after a while, and the big discovery happened here, with the my colleague Steve Gatesy who was cracking rock and discovered this, I don’t know if you’re going to see it but you 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, turns out
it’s the snout of a fish, and not just any fish, a flat-headed fish. You could tell it was flat-headed snout. So remember I showed you before, conical head, flat head? Here I had a flat head
sticking out of the cliff, looking me in the eye right. So I kind of knew we’d found
what we were looking for. And so what it became then, was to remove these things very carefully. As we remove this one,
we found about four more of these flat headed fish,
we now have about 20 of them, in various states, from individual bones to whole skeletons, to the skeletons we have about five. So come home on the bottom
of the helicopter anyway. So when these came back,
it was in the fall of 2005, the preparators take
over and these are people who work with a needle and pin, and these things come
back encased in plaster. And this is Steve’s specimen, they sit for months of the time, this took several months, Fred Mollison in Philadelphia did this, removing the rock grain by grain. And here you can see after
about six or seven weeks, 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, looks like you’re dealing
with the top of a flat head. A few more months go by, and this was starting 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, it looks like we have a neck with no connection of
bone to the shoulder, this thing got really interesting. As this was happening, a trial was going on in Pennsylvania, the Dover trial, Kitzmiller
case where intelligent design. And some people were
saying during that trial, that whether that there
are no transitional 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 380 million years ago, here’s a early limbed animal, from about 365 million years ago, here’s the new fish, I use that term for lack of a better word. What it is, we have the extended size from about a foot and a half
long to nine feet long. The creature here is 4 feet long, and only I’m showing you the front half. You can see it had scales on it’s back, these have been squashed in, scales on it’s back and a fin, fins with fin wedding, yet it has a flattish
head with eyes on top. It has a real neck so
it’s lacking an operculum, which most fish have. So it has a mosaic of
features of both fish and land living creatures. So you see as a mosaic
like a lobe-finned 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, limbs, heads and so forth. So being the discoverers of this creature, we got to name it, and so we wanted the name to
reflect its Inuit heritage. We worked there with the permission of the Inuit government, and the Inuit elders, they were very helpful to us, and we wanted the name to
reflect it’s provenance. And so we had a naming
project where we engaged the Nunavut elders, these
are the Nunavut elders here, to come up with a name
to meet two criteria. Criterion number one, was a name that was
meaningful to them and to us. And number two, was a name
that we could pronounce. And this is the name of the committee, so that secondary, didn’t
lend for a lot of confidence that we have a name it yeah. Anyway so um, 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 the streams or ocean. Like no no no, it’s a fossil, and there were so many gaps in
the way to communicate here, 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 just say so, “you have yourself a Tiktaalik.” I said, “A Tiktaalik, what’s that?” He said, “It’s a large
freshwater fish in our language,” So that was the, um, how the name stuck. But anyway back to the biology here. The um, so we had several of these things, and 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 this is all about. And so here you’re looking at
one of our large specimens, about nine feet long, and you see here’s a lower jaw, here’s another lower jaw so you’re looking at it like
this, two jaws like yay. And it was one specimens like these, that we started take limb bones apart. So we found here’s an
upper arm bone, a humerus, 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 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 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 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 amphibians, creatures for lack of a better word. And we can compare them up and down the file in 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 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 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 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
can see where they’d fit on, and you can see how this one facet, which sort of rotates
this down this side here. That means this bone could rotate far down into the plane of the
slide, that’s important, 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 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 have three 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. In Acanthostega, this early limbed animal, the humerus or upper arm
bone is coming out at you, like this, like a crocodile,
so the limb is held to the side of the body. Whereas in fish like Eusthenopteron, 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 in Acanthostega, and backwards in Eusthenopteron. And then you just add the other bones in. If you add the forearm
bones, the radius and ulna, 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, and work with a motion called pronation, like moving your thumb inwards. And when you add the other bones in, we can begin to see what
Tiktaalik was able to do. Tiktaalik is specialized
into a form of a push-up, with elbow bent and wrist extended, with a small set of
palmish bones it could, and remember the fin webbing
is sticking out here as well, you can support the body
in a form of a push-up with a palm-equivalent
flush against the ground. What was nice about these specimens too, and it’s something we
haven’t really published it, is the notion that we can begin to see how the fin webbing
changes during this change. So you’re looking at 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 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 and these big rods, is over the elbow joint
and over the wrist joint. Which totally makes sense, those are the areas
where the fin would bend. So this is a sort of more
or less what we think what the fin of Tiktaalik was able to do, function like a paddle, or like a prop, enabling the creature to do a push up. This is the reconstruction of
Tiktaalik as it was in 2006, as a flathead with eyes
on top, pair of nostrils, 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 the, a whole series of opercular bones. It has a fin webbing and
inside that fin webbing is an upper arm bones,
forearm bones the equivalence, and both proximal carpal
and distal carpal bones that is the equivalence 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 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 we are going to get to. One of things about Tiktaalik, is if it’s supporting itself
as the appendanges suggest, on the ground like in a push-up, that’s when the neck
becomes comes quite handy. If you look at 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 head to the shoulder. They function in
breathing in fish as well. They’re pumps that draw
water across the gills. One of the big changes in
the transition to tetrapods, the 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 the 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 mouth. So what’s Tiktaalik specialized to do? Here’s the reconstruction
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 water and land, and to feed as a carnivore, to feed either on fish or on the large variety of invertebrates that are present on land, and in the air at this time as well. So if you look at the
family tree and you plot with all the various
characters that we can do, Tiktaalik turns out to
be very closely related 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. Remember I opened with up the fact that this is an integrative discipline, this is something we have to pull in data from many different lines of inquiry. When 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 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 they can, what lessons
can we learn from them about how fish evolved to walk on
land and to live on land. And there’s a couple things, I’m just gonna to 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 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 can do
with, this is arbitrary, I could add in another four
or five things on here, but I wanted to give you
some take-home messages about what we can learn from living fish. Well if you look at it, what I’m going to 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’re compare to fish
fins that are alive today they don’t look a whole lot alike. Here’s a lungfish here, a creature Neoceratodus from 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 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 we 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 the ones that have been
dead for 375 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? It’s size and shape and so forth. And if we do that we can begin to see, and by about the late 90s 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 going to go through them all, that characterized the
development of limbs. It’s a cascade of events, of cellular events and genetic events, that produced the pattern of limbs, I’m going to 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 and the
skeleton of the fins of fish, and indeed that pattern
them, are very similar to those that pattern the
limbs of limbed animals. And in fact it’s very clear that you know, if you were to ask the question, are there any new genes that are patterning the
limbs of limbed animals that aren’t in present in fins. The answer’s 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 want toolkit, that’s necessary to build appendages, was already present when a lot of these fossils hit the scene. So 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 famous among this is the mudskipper. Mudskippers can live on
land for a period of time, about 24 hours about the max in the mud, and they have appendages but
the little type of elbow. And if you look at frog fish, the frog fish is a creature
that can walk in the water, this is actually an aquatic
creature they 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 other creatures evolved appendage support, they evolved 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 of ourlineage. Finally you can ask the question you know, the creatures that are
doing appendage support and walking in mud and so
forth, how 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 30,000
different species of fish, say 29,000 of them or so. Of those that are looked at so far, in the last major monograph
somebody identified 375 species of air breathing fish, which is what’s been looked at, there are certainly a whole lot more, in 49 different families
and if you map it to a tree, it evolved at least 24 times. That likely is about three times to love, based on if you look at
the trees that 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, at least in the evolutionary tree, is they use lungs. In fact lungs are primitive, lungs are primitive to this
thing here, a Polypterus, to lung fish, 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 were around in Devonian streams. They evolved in each case
like in the lung fish they evolved to allow creatures to breathe when water gets anoxic and oxygen poor, they go up and gulp air
in many different ways. And there other examples as well, there are diverse air breathing
organs in this group here which is very specious. Some of these creatures
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. With air breathing evolving
multiple times independently 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. 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 and only evolved once. Perhaps it’s some sort of
ecological king of the hill situation where, you have an incumbent, and it sort of displaces
any other lineages that would evolve to walk on land, ’cause there’s already an
incumbent set of species there. So all this is in terms
of its extrapolating to great transformations. You know 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 kin were sitting around thinking, oh golly I wanna to evolve
lungs so I can walk on land, I wanna 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 mud flats 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 evolving. And I should say that
there is a unifying theme to many of the great transformations, I’m gonna just close
with a series of these. 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 creatures with transitional features between acorn worm and
fish and I should say, some of the most important
species in this transformation have just been discovered
in the last 30 years. You could say the same thing with any other great transformation. Take whales and their derivation
from four-legged creatures about 50 million years ago, you could find fossils that have a series of transitional features
leading to whales, 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 20 years. And the same thing is true with the shift from reptiles to mammals, 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 and understanding the great transitions
in the history of life, have been discovered in the last 30 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 understanding their genes and genomes and sequencing
in an ever rapid clip, to understand the the
genes that build bodies, and control development, to understand the
biomechanics of the features that these creatures
use to walk and to live, to understand the ecosystems and the systems that
function as ecosystems and the food webs, the ways these creatures
would have interacted. Nowhere, 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
fundamentally integrative field, and an integrative biology. Thank you very much. (audience applauding) (gentle music)

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