Evolutionary baggage

Transcription

NEIL SHUBIN: By your inner fish I mean that in every organ, in every cell, in every gene of our body we contain at least 3.5 billion years of the history of life. What that means is our story, the story of why we look the way we do is really contained and understood by understanding the bodies, the embryos, and the DNA of other creatures, creatures as different as primates, other mammals, lizards, flies, worms, jellyfish, even microbes. And our stories, our connections to the rest of the natural world are so powerful that they can be predictive, that they can tell us something about what we would expect to find in the fossil record, and what we expect to see in our own genes. Now, my own way point in this is truly fish. I mean I could have chosen flies. I could have chosen the history we share with jellyfish, and so forth. But really my history, and this actually began at Harvard in the mid 1980s when I was in a graduate seminar run Farish Jenkins, who's here tonight. And Farish was running a seminar on the origin of land living animals, tetrapods. And what you see here is a diagram that really captured my imagination. It was done by one of my predecessors at the University of Chicago, Len Radinsky in 1987. And what Len showed here in this very simple diagram is a fish on top, what we call lobe finned fish, a creature that first appear in the fossil record over 380 million years ago. And an early limbed animal, creatures we call tetrapods, they became land living animals, all from about 365 million years ago. And I remember looking at this diagram, golly, what a great transition in evolution. Going from water to land. Changing in sort of the biological role of every organ in the body. From fins to limbs. Changing the structure of the head. Changing in dealing with water to dealing with gravity. Everything had to change. Can we understand this? How would we do that? So it's a great scientific puzzle that I wanted to explore. And really my first goal was to find fossils that really bridge this gap between lobed finned fish and limbed animal. So what I did was I applied the rules that I learned from Farish when I was here at Harvard. And that is to discover new sites that contain important fossils about the history of life you really look for places in the world that have three things. You look for places in the world that have rocks of the right age to answer your question. So I'm interested in this transition from lobed finned fish to limbed animal. No great secret, I'm interested in rocks about 370 or 375 million years old. You look for places in the world that have rocks of the right type to preserve fossils. Now, as paleontologists we come to know these by other discoveries that people have made, and by our understanding of sort of the evolutionary biology of these animals. And the third thing you look for-- Well, it does me no good if my wonderful rocks of the right age and the right type are buried five miles underground. Those rocks have to be exposed at the surface. And so when you open the pages of National Geographic, where are paleontologists typically working? They're typically working in deserts where the rocks are exposed. So I applied these three rules to lead one of my first expeditions. And I forgot one of the major rules. And that is lack of money and inability to take risks. So I started my first academic job at the University of Pennsylvania here in southeastern Pennsylvania. And as a young assistant professor what I wanted was a research program that was kind of cheap, cause they didn't have a lot money, and was kind of risk free that I could do out of my car using turnpike tolls and gas money. And in doing that I applied my rules that I learned from Farish. And I looked at the geological map of Pennsylvania you could see here. I stripped it of everything unimportant to show you the Devonian age rocks that are extensively mapped across the state of Pennsylvania. Devonian is the age of fishes. And remember I was telling you that we're looking for rocks around 370 or so million years old. These are in that window. It got better when I looked at how these rocks formed. If you want to think about what Pennsylvania looked like 370 or so million years ago, get Pittsburgh, Harrisburg, and Philadelphia out of your brain, and think Amazon delta. What you had was sort of a series of highlands to the east, and an inland sea to the west, kind of where Pittsburgh and Cleveland are today. And a series of rivers like the Amazon delta that drain from east to west. Now, if you're a paleontologist, interested in finding fossils that tell you about the transition from life in water to life on land, this is perfect because you can sample all kinds of ancient environments, from ancient estuaries, to meandering streams, and point bar, and sediments, and so forth. It was really ideal. There was another piece of good luck that happened to me then. It was that a young graduate student joined my group to work with me. And that's Ted Deschler, shown here. Ted an I worked in these rocks in Pennsylvania for a number of years. And we continue our collaboration today in the Arctic expeditions I'll describe for you a little later. Now, so I told you, Pennsylvania has rocks of the right age, rocks of the right type, I had this wonderful, promising graduate student, Ted Deschler, to work with. There was one tragedy about being a paleontologist in Pennsylvania is that it's not a desert. It's not known for its exposures. Indeed, my research program with Ted to find fossils became following the Pennsylvania Department of Transportation around when it decided to put in new roads. When PennDoT would put in a new road, what would it do? Well, they'd come out with their trucks and they'd blow stuff up with dynamite. That's perfect for me if they were blowing stuff up in areas where Devonian rock was exposed. So this is an area here. This is called Red Hill, Pennsylvania. The name is not particularly clever because it's a red hill in Pennsylvania. It's about an hour north of State College. And here you can see the strata or the layers here. And these represent cross sections of ancient streams as they dried up, as they filled up with water, as they meandered around. And if you looked at these in cross section they really would look really real streams, with pebbles on the inside, and fine grains on the outside, and so forth. And here you see our cars for scale and a human being. And the research, for scale. And the research was climbing all over these cliffs finding fossils. Well, we started this in like 1991. And we were climbing all over these hills. And we started almost immediately to find cool stuff. Teeth the size of railroad spikes. We started to find jaws of these creatures. I'm just going to show you Ted holding one of these front jaws. Jaws as long as your arm. This is the front end of one of these things. So these teeth the size of your thumb were sticking out of a jaw the length of your arm. Remarkably horrible creatures, 16 feet long, that we were discovering in pieces. All kinds of other fish were coming out. Here's a sidewall of a fish. So its body armor here. A little bit of its head kind of squashed up. But this is a lobe finned fish. Remember that fish I showed you in the cartoon in the beginning? This is a version of one of those things. And then pretty soon we started to find limb bones of early tetrapods, early limbed animals. And here's one here shown in six different views. It's one bone. I'm showing it as we do in a scientific publication to orient it in the ways that are maximally informative for my colleagues. And here's a reconstruction. And if you're going to find one bone of a limbed animal, humorous is a great one. Shoulder's another good one. But the humorous can tell you a lot about the posture if it's well preserved. So this particular bone, even though it was a single bone, was remarkably informative for us. And we were able over time, over about six years of working on these sites, to reconstruct what it looked like. I mean, here you see that cross section of streams I showed you in Pennsylvania, Red Hill, Pennsylvania, that's what one of those cross sections would look like in time. Some of the earliest forests. Huge amounts of shrubs. Land plants are becoming unbelievably diverse at this time. It's a small, shallow, sort of meandering stream with that giant monsterish fish. Remember I showed you the teeth of it before. Lots of little armored fish. And all kinds of limbed animals, tetrapods, that we were finding as isolated bones. It quickly became clear that we had a problem. Remember I told you my goal. My goal was to bridge this gap between lobe finned fish and limbed animals. But what we're already finding are very, very well developed limbed animals. And it was pretty clear from looking at this that we were probably in rocks too young, and rocks about 365 million years, too young to answer the question we're after. We would have to move back in time. And just to step back, I just want to show you what the major features we wanted to understand really were. What you see here is that Radinsky slide again. And you look at the fish on top, and you look at this limbed animal on bottom. You see they look very different. And you look at the head. You go from a lobe finner fish, which has a conical head, with kind of eyes on either side, to an early limbed animal that has sort of a vaguely crocodile shape to its head. It's a flat head, with eyes on top. Indeed, the proportions of the head change as well. The front end becomes very long relative to the back end. Another big change that we wanted to understand was fish don't have necks. They have a head that's connected to the shoulder by a series of bones. So when a fish wants to look around, what does it do? It swims around in water. Whereas early limbed animals have a neck where the head can move independently of the body. You know, the fish have scales on their back. And these early limbed animals don't. And importantly, another big thing is fish have fins. And these early limbed animals, as the name implies, have limbs with fingers, and toes, and wrists, and ankles. In working in Pennsylvania we were finding lots of these things in bits and pieces, but no whole skeletons. And we really weren't finding creatures that were sort of helping us bridge this gap. And, in fact, I could spend the whole talk tonight telling you the differences between these different groups, and we weren't really making a whole lot of headway there. Because what we wanted to do was really find a creature that in the evolutionary tree-- Here's limbed animals. So you're one of those, right up here-- that are sort of closely related to them. And when we look at the finds that had been made at the time around the world it was pretty clear that if we were to move back in time we had a better chance to find the species with transitional characteristics that we were very interested in finding. Earliest limbed animals from like Greenland and other places were about 365 million years old. And the others creatures first appear about 390, 380 million years ago. Some of them continue up in the fossil record, but that's when their first appearances are. So it became clear we had to shift our focus. And so what did we do? We applied our rules, looking for places in the world that have rocks the right age, rocks of the right type and exposures, dug out geological maps, all kinds of stuff. We had plans to work in Brazil, Antarctica, western North America. And everything changed one day in my office in the winter of 1998. Ted and I were having an argument, or a discussion. It was an argument. There was a point of fact that we had to find out. So I pulled out an undergraduate geology textbook that was in my office, this one. Dott and Batten. It's the second edition. It's now I think in the eighth or ninth edition. Settled the debate. And in paging through the textbook, you know, he and I were just chewing the fat, and to wallow the time I was just sort of paging through the textbook, hit a figure in Dott and Batten, this textbook, which sort of captures what we look for in a nutshell. So let me spend a second on it because it's very relevant. The title of this illustration is Upper Devonian Sedimentary Facies, which mean rocks that could be of the right age, and of kind of the right type, could be of the right type to preserve the fossils we're interested in. And you see a map of North America here. Right, there's Greenland. And superimposed on that map is an interpretation of the environments that these Devonian age rocks formed in. So the legend goes that these were formed in an ancient seaway. But then Dott and Batten in this diagram identified three areas that had ancient delta systems like the Amazon today. The first one that we identified, and I've shown in red, is here. Well, we're familiar with that. I was just showing you those rocks in Pennsylvania. Those are the Catskill rocks. Ted and I were familiar with that. They produced lots of fossils. East Greenland. This is where one of those limbed animals I showed you before came from. Very famous from studies done in the '20s and '30s. Well known and very productive in fossils. And then what stopped us dead in our tracks on this morning was this. Extending 1,500 kilometers east to west across the Canadian Arctic a huge vast expanse of mapped Devonian age rock, formed in ancient delta systems, completely, and very importantly, unexplored by any of our colleagues. That's another important variable. So we were really excited. So indulge me as I go on a little history about these rocks. And it's truly fascinating. And it begins with one of the great exploration vessels of all time, the Norwegian vessel The Fram, which in Norwegian means forward. It was designed by Colin Archer under the inspiration of the great explorer Nansen. And this is The Fram here. Nansen worked with Archer to design The Fram to take him on a run in the late 1800s to farthest north, towards the North Pole, and was designed to flow with the ice currents. So it's a very, very strong ship. About 30 years later this ship was to become famous again as it carried Amundsen on his successful conquest of the south pole. So it did farthest north for a period of time, and it did farthest south for all time. Really remarkable vessel. In the interim it carried this crew up to what's today the Canadian Arctic. It was led by this gentleman, Otto Sverdrup. He does not look like a very humorous man. Not a whole lot of jokes, I would imagine, in the Sverdrup crew. But he carried this sort of hardy bunch of Norwegians, who over wintered for several years in what became known as the Canadian Arctic. And as they over wintered there were a number of naturalists just like Darwin and so forth, who would get off the ship, and map the geology, collect the bugs, the plants, and so forth. Important here, and one of the heroes of our story, is this young man here, Per Schei. So what they did is they overwintered. This is the map of what they did. And it was an expedition that ran from '98 to '02. And they spent time on these fjords here on southern Ellesmere Island. And I can only imagine overwintering at that time was like in this vessel. And at that time, Schei, a young man of about 28, would get out of the ship and collect rocks. Well, he didn't want to collect rocks. Turns out during this interval he collected in this little fjord here, which he mapped, pieces of fish, little bones of fish that he mapped out. And he kept them in his log notes, and so forth. And there they sat. They were essentially lost to science for a period of time. And unfortunately one of the tragedies here is Per Schei was to die, to pass away young, soon after returning from the Fram Expedition. He returned in '02. I think he passed away in '04. Cut to 70 years later when this gentleman, Ashton Embry, a great geological mapper of the Canadian Arctic out of the Canadian Geological Survey in Calgary. Ashton was charged with mapping the age of the rocks, and the deposition of the rocks, and the stratigraphy and layers of the rocks across the Canadian Arctic. And he produced a marvelous paper, which we found this morning in 1998. And this is the title. It's got this hard title to say. Middle Upper Devonian Clastic Wedge of the Franklinian Geosyncline, Embry and Klovan, 2000, 1974. You say why am I showing you this? Well, one page of this launched our expedition up to the Arctic. And this is the page. And there are two pieces of it that were relevant. The first is when he talked about the age of the rocks up there he said, "The available data indicate an age of early to middle Fronian." To translate that for you, remember the question mark I showed you before? The age of these rocks is at the question mark. Then there was one that really stopped us dead in their tracks. It says, "The Fram formation is similar to the Catskill formation in Pennsylvania." OK. And it's unexplored. And if it's in the Arctic there's not a lot of plants on it. It's probably exposed. We are out of here. And this photo caught our eye. And this is the kind of exposure you look for if you're a vertebrate paleontologist. Because you just want to crawl over that thing, and look for the little bits of bone that are weathering out of the surface. And so this is what Ashton did. So we're working what's today Nunavut. There's the North Pole. There's the flag in Nunavut. There's the Nunavut territory right here which I'm going around with my pointer. And let's zoom in. Let's zoom in on Ellesmere Island here. This is Ellesmere in the zoom, right here. And he mapped across Ellesmere, and all the way to the western part of the Arctic these exposures of Devonian age rocks. And he named the key formation that's similar to the Catskill of Pennsylvania, the Fram Formation after the Norwegian vessel. So Ted and I found all this in the winter of 1998. And really this morning we dug all this stuff up. And we were literally shaking. I mean, as a paleontologist it's rare that you get something like this completely handed to you. So we did what anybody under such circumstances would do. We went to lunch. And we went to Chinese for lunch. And I had my Kung Pao chicken with the hot and sour soup. And I got a fortune cookie. And the fortune cookie said, "Soon you will be at the top of the world." All right. We were out of here. There's a challenge though, because this is not like where I drive my Subaru wagon to central Pennsylvania. I mean, what we're doing is going here. It's all the way up there. It's daylight 24 hours a day in the summer. It's far away from anything. There are polar bears up there. Polar bears eat people if you're not careful. It's a hazardous place to work. I mean, to give you a sense of things here is the nearest town to our sites. It's about 200 miles away. And this is a picture of that town of 170 people in spring. OK, so a lot of challenges. So the subtext here though is if you want to pull something like this off, experience. And, importantly, there was one person who has made a career out of exploration in the Arctic, particularly doing vertebrate paleontology, who had the tool kit, the patience, the expertise, and the persistence to help us pull this off. So I called Farish Jenkins here at Harvard University, my mentor. And Farish and I had always talked about working together. And I ran this idea by Farish. And he said, oh, let's go. And I was like, yes. And so now the team was set. Farish, Ted, and me were going to the Arctic. This gives you a sense of what life is working up there. Here Farish and I are soaked to the bone. It's probably just sub freezing. We're trying to wrap fossils in plaster, which is probably not working at all well. But look at our faces. We're smiling because we're happy, because we're finding fossils. That's the spirit of that collaboration. So to get around here we used this very fine and sort of long supply chain, which is sort of a fine interplay between aircraft that can land on the tundra, twin otter, and helicopters, since we're really far out there. And this actually constrains the kind of science we can do. Because we can't bring a big crew. This is kind of like what stuff looks like before we pack it into the plane. These are the people. We did bring a small amount of stuff. We bring a small number of people, and they all tend to be small. So we optimized the weights. Except for me. I'm usually kind of overweight. By the time we go I lose a lot of weight there. But this is our food. We pack it in these tubs and so forth. And so weight is a precious commodity. And so what we have to do is when we're in the field we have to make very careful decisions about what comes with us, because fossils are rocks, and rocks are heavy. And we can't get everything home that we find. So we started. We were so excited. And we started in 1999. So we had the fortune cookie in 1998. We went there in 1999. And the decision for a lot of reasons, some of them logistic, was to work in the western part of the Arctic. And we went to here, Melville Island, and Bathurst Island. This is what camp looks like. We each have our own personal tents. They withstand high winds. This is the kitchen tent. It doesn't withstand as high winds. But it's a very nice tent. And what we do is we tend to camp near snow fields, drink the water right out of the snow fields, and then walk, spend our days just walking for the exploration, just going over this bedrock here. And what we're doing as we're looking at this bedrock is trying to see where bones are weathering out in the hopes that we can perhaps find a layer. This 1999 season was a failure, but a useful failure. It told us not to go to the western part of the Arctic. Because basically what we were in was sort of the ancient sea. We had to move back into the streams, to move upstream, and moving east to Ellesmere Island. So we were fortunate to be able to return in 2000. And that's what we did. We returned to southern Ellesmere in 2000. And this is what camp looked like there. It's a lot more montane. There's a lot more relief. As we moved east we got into the stream sediments, the layers that I showed you that are similar to-- Remember, I showed you that Red Hill exposure? Well, very much like that in some places where you have ancient streams shown in cross section. And as we did that we started to find fossil fish. There are a lot of challenges working in the Arctic. I just want to spend a second or two on those. So when you first go to the Arctic, basically if you're standing here, you look at that cliff right there and you say, oh yeah, I'm going to walk over there, it'll take me an hour. Ha, ha. No. There are no trees for perspective. So things are farther away then you actually sense. And so that can actually create problems some times. So you got to really kind of keep a sense of that. And also the walking can be horrible there. Sometimes you have this sort of scree and talus, which is very mobile, sometimes consolidated by ice, or even worse, mud. I've spent many a time having sunk in the mud up to my knee. Actually one time up to my waist, which was no fun. But none of this is actually easy walking. It's harder to work there than you can imagine. My summer home, just like everybody else in the field crew here, is a tent. Which usually, and this was in a year we had a pretty bad storm, where we would build wind walls to hold the tents up. We are armed because of the polar bears. We have to carry firearms. Radios. The logistics has to be fairly precisely run. So this is a picture of me last year. And I show you what we want to look for. We were walking around. Farish and I were up here last year actually. And I just thought this would make a great slide of what we look for. And what we look for is this. I'm standing here. That's me. This is a rock, and there's fossils coming out of these rocks. See everything that's shiny here? This is a trail of bone that's weathering out of the cliff. That's what you look for. Because when you look carefully at it what you'll see is, here's some of the mud and the rock, but each of these things that looks different from that is more or less bone. And then we follow these trails to the layer where they're weathering out, and if we're at all lucky we can find a layer, or a specimen, or something like that. One of the big insights to our discovery actually happened here at this site. And this is a site that produced, actually was ultimately to be the major site. It was discovered by our youngest crew member, Jason Downs, who was a college undergraduate from the University of Pennsylvania at the time. This is the site that Jason was to discover a few hours before he discovered it. About five hours later Jason was to walk over this layer right here. We didn't know it at the time. We had returned to camp. And we were all sitting in the kitchen. 7 o'clock was rolling along. We were making dinner. And somebody asked, where's Jason? I don't know where Jason is. I haven't seen him. That's a problem. Our youngest field crew member got separated. We usually go out in pairs. Nobody saw Jason by dinnertime. And we were actually getting quite worries. We were actually a little more worried when we heard these footsteps coming up to the tent, zipper opening. Jason runs in, and his eyes are like orbs. And is he being chased by a polar bear? What's happening? But it became very clear what was going on, because in every pocket of his parka, and in his rain pants, were fossil bones. And he was pulling them out on the table. And bone after bone after bone, handfuls of these things shown here. These are lungfish plates, lobed finned fish bones. So it was dinner time. But it's daylight 24 hours in the Arctic. Dinner could wait. We grabbed chocolate bars, or whatever else, and we ran to Jason's site. This is us that night, probably around 11 or midnight, something like that, crawling Jason's site. So basically what happened is Jason walked over this layer. And you see it's sort of greenish here. It's greenish in part because there was a carpet of fish bones, thousands of them. And we were just picking them up. And the challenge here was to trace this up to a layer that we can dig in and maybe find articulated specimens. It turned out not to be easy to do that. Nothing, by the way if you get the message here, is easy in the Arctic. And the problem here is, see these cracks? You'd think following these bones up to a layer would be easy. But what you have in the Arctic is in the winter it's really, really cold, and in the summer it's less really, really cold. So you go through this cycle of a really, really cold, less really, really cold, really, really cold. And freeze, thaw goes on. And it churns the upper layers. And as it churns those upper layers. As a paleontologist it makes finding the layers very difficult. You have to sit with it for a while. And it took a while actually to learn it. But find it we did. Here's Ted, and Corwin Sullivan, a Harvard graduate student, when they found the layers. And here you see the layers as they're exposed. And as Jason's site was exposed his layer turned out to be those thousands of bones were produced by fragments of skeletons, some of them articulated, some of them partial fragments, piled one on top of the other. Whole fish skeletons. It was really, really, really, really wonderful. So what we did is open this up. This is what the site looked like in 2006. Opened it up as a big hole. But the real discovery of one of the main specimens happened in a remarkable year. We almost did not return to the Arctic in 2004 because we weren't being successful. We decided to return, just give it one more try. And in the fifth day of the field season-- It took us a while to get out in the field that year-- In the fifth day of the field season we're digging in Jason's layer. And my colleague whose back you see here, Steve Gatesy, who's at Brown University, was pulling rocks. And he pulled a rock from right here. He said, hey guys, what's this? We looked at it and we saw, well, here's the rock. See here, this is bone. See this V shaped thing? See this V? It's like a V, this little seam there. Turns out that's an upside down snout of a flat headed fish. The minute we saw that we knew we found what we were looking for. Remember I told you conical head to flat head? Here we had a flat head sticking right out of the cliff at us. And if we had any luck, and hopefully our luck was about to change, that the rest of the skeleton would be preserved in the cliff. And Steve did an absolutely masterful job. He's an artist. And he was able to do this really beautifully, to sort of etch around it so we didn't take the bone out, not exposing the bone, but just to rough it out so that it could come home as a boulder. As we did that here's Farish's back. A specimen opened up on Farish' back. I was working down at the bottom of the hill, somewhere like three feet underneath my feet here. And I found another specimen. We had three wonderful specimens of this flat headed fish, ranging in size from about four feet long to one, it's partial, but would've been about nine feet long complete. Now, the challenge here for us became to get these things home. And they come home in a helicopter. So they get wrapped in plaster for the trip home. And then they arrive back to the prep lab. And it's really in the prep lab where the preparators working under a microscope with tools expose the bone from the rock grain by grain. Let's look at Steve's specimen. Remember that little V thing I showed you before. It returned to the lab. And the preparator, Fred Mullison in this case in Philadelphia, was using a pin vice with a needle like this, removing the rock grain by grain. And here you see Steve's specimen. So you have the top of a head sort of emerging here. There's an eye. And there's an eye hole. We call them orbits. Several months go by. This does not go quickly, OK. Several months go by, and here's the flat head. See the flat head. There's a lower jaw. There's the flat head. There's one orbit. There's another orbit. Hey, it looks like we're getting a shoulder. There's another shoulder here. Hey, but there's nothing connecting the shoulder. Maybe this thing has a neck. This thing is revealing itself over time. And specimens that are being prepared out. And just to give you the take home, here's a fish. Here is a tetrapod. Here's the new fish. This is the type specimen. So it's a creature that in totality would be about four feet long. We basically have it from the tip of the snout to the pelvis, to the hip. We don't have the tail. But you can see scales on its back, like a fish. There's a whole row of them, beautifully interdigitating. Here's a fin with the fin rays. But like an early limbed animal it has the limbed animal proportions, a flat head more or less, with eyes on top, long front end of the skull, short back end of the skull. Has a neck where the head is separate from the shoulder. And what became really amazing is when we flipped this thing over and looked inside the fin webbing, we saw bones that correspond to our shoulder, elbow, even portions of our wrist. Two portions. What we call the proximal carpus and distal carpus. Here found at the right time in the fossil record, at the question mark, was a transitional species between fish and land living animals. So this is the creature here. And just to review, like a lobe finned fish it has fins with fin rays. It has scales on its back, primitive jaws, lots of other features too. And like a land living animal it has a neck and sort of proto wrists. Put quotes around that. A flat head and sort of limb proportions of the early limbed animals. Expanded ribs, which I'll show you in a second. Now, Farish, and Ted, and I knew exactly what we had. We were really excited. And by the way as discoverers we're given the privilege of naming it. And there was a decision that the name should be part of a naming project with the Inuit people, because we were working up in the Arctic at the pleasure of the Inuit people. And we wanted a name that's meaningful to them and to us. So we engaged the Nunavut community of elders, which is the group right here, for a naming project to come up with a name that met two parameters, one, that it's a name that's meaningful to them and to us, and, two, is a name that we could pronounce. And the name of the committee did not lend me a lot of confidence that we could pronounce it. So I was tasked to be the liaison in this case. So I was calling, and I would talk to this guy. And it was surprisingly difficult to describe it in a meaningful way because they had no concept for fossils. So the first conversations were like, we found a fish. We want you to name it. He said OK. I said we found the fish, and it's a fossil. We found it in rocks. Long pause. Hunters don't find fish in rocks. They're in the ocean. That kind of thing. So it took us a while to get to it. It was actually kind of frustrating. And finally he said, look, just tell me what it is and what it looked like. I said, well, it's a large freshwater fish. He said, oh, why didn't you say so. You got yourself a tiktaalik. I said, a tiktaalik? What's that? He says, the large freshwater fish in our language. [LAUGHTER] So there you go. There was another synonym for it, but we ended up going with tiktaalik. So we had a number these tiktaaliks being prepared out. And what was beautiful about it is that we had a lot of specimens, and a lot of specimens, not a lot, three or four good ones, that we could take apart. This is an underside of a skull. So you're looking at the lower end of the jaws here. And we could take it apart and begin to see what the fin looked like inside, taking all the bones out. And this is where the preparators work becomes really essential. Because a preparator has to sit here with a needle and remove this thing, and then clean it off months at a time, each bone individually. And that's exactly what happened. And this is what the fin of tiktaalik looks like. It's upside down. But here's the shoulder up top here. Here's the upper arm bone, the humorous. Has two bones just like we do, radius and ulna, here, and a series of bones what we call distal, further away. And we were able, the preparators at least, were able to show us what the joints look like. Here's the shoulder joint of tiktaalik. It's got a ball and socket, but then it's got this funny sort of little cam stop up there, which tells us how motion was restricted in certain ways. Here's the elbow of this fish. This is the end of the arm bone, the humorous. And if a set or an area where the radius and ulna would fit in, it tells us how this thing would bend, how it 'd flex. And then the mobile sort of wristy areas. So what we can do is begin to think about this thing as an animal that's built to support itself on its appendages, that it's uniquely able to flex at the elbow and sort of extend itself at the wrist area. Think about when you do a push up. What happens? You have a palm that lies flush against the ground, and you're pushing off with your pectoral muscles. And you're extending your elbow. That's exactly what tiktaalik was capable of doing. Because we can see from the massive pectoral musculature, and the motions of the fin are able to do that. In a fin that also has fin rays. So it's sort of a dual purpose organ. And so this is the reconstruction of what we had of tiktaalik in 1996. So you can see this creature with a flat head with eyes on top. Has a pair of nostrils in front here. Has a neck where the head is separated from the shoulder. Big, massive shoulder. A fin with fin rays, and a humorous, radius, ulna, you know, shoulder, elbow, even portions of a wrist. This was a true surprise seeing these massive ribs of this thing that interdigitate with one another, suggesting that this animal is undergoing sort of gravitational stress, that it has to support the body of the abdomen under a load. Really remarkable animal. And so the other thing is, if you look at the transitions here-- So fish don't have necks. This is a lobe finned fish. And you'll see it has this sort of flat, bony flap here, the operculum, which serves as a pump that pumps water across the gills. If you look at land living animals they have a neck, and they've lost that operculum, which moves the water across the gills. And the whole proportion of the head has changed. Tiktaalik is wonderfully intermediate in these regards. Not only in the proportions. But also in the fact that it lost the operculum, and clearly has a mobile neck of sorts. So it's a remarkable system. What we're seeing is a coordinated change of evolutionary changes that affect mobility of the head, support of the body, and breathing, respiration, a shift in the operculum suggests a shift in breathing. So a number of ideas about how tiktaalik could have functioned. It could function on the water bottom as a benthic creature. It could function on the mud flats and the shallows as a creature on the margin. So it was really wonderful for us to see, Here we had this gap in the fossil record, by targeting fossil discoveries to key times in the record we can begin to fill that gap by fossil discoveries. And so you can ask the question, you know, so who cares? How is this fish to tetrapod transition relevant to anything? And I can give you many answers. But one important one is very personal for all of us. That is when I'm talking about the origin of a neck in a creature like tiktaalik, which we see in tiktaalik and it's evolutionary cousins, we're talking about something that was to become our own neck. When I'm talking about the origin of sort of a mobile wrist, proto wrist in a creature like tiktaalik, it's something that's going to become our true wrist. So we're seeing many of the features that are evolving at this transition are actually important parts of our own evolutionary history. And indeed we can trace these things from fish to humans quite nicely. Now, the inner fish conceit was really sort of born when we found tiktaalik, or we were beginning to find tiktaalik. And I was teaching human anatomy at the medical school at the University of Chicago. And I was the course director for years. And I had taken human anatomy here with Farish Jenkins and Lee Gehrke, at the wonderful Health Sciences and Technology Harvard MIT program. And it didn't feel unusual for me to be a paleontologist teaching anatomy, because that's my tradition. But I remember when I started teaching anatomy-- And you think about anatomy for a second. This is a very formative course in the first year life of a medical student. And this is really see the human body for the first time in a cadaver, where they learn thousands of new names and new structures, really encounter many things, from the body to mortality, for the first time for many of them. Very stressful experience. It was very stressful for me because I had never taught the course before. And so in the first few weeks I'd be talking to students around the table. Just spend a lot of time talking to students around the dissecting table. And the students would almost uniformly ask me, what kind of doctor are you? Are you a surgeon? Are you a cardiologist? I said, well, I'm a fish paleontologist. They're like, I want my money back kind of look is what I'd get. But it became really clear being a paleontologist, and not only that, a fish paleontologist, is a very powerful way to teach human anatomy. Because the basic road maps of much of our body, to the way our limbs put together, the way our head is put together, the base of organization of so much of us is first seen in fish. And fish are the basic roadmap for who we are, and our own appendages, our guts, our brains, our nervous system, and so forth. And this is abundantly clear at the most stressful moment of Human Anatomy. The most stressful moment of the Human Anatomy course is where students sort of look at the syllabus, they see they're halfway done with the course, and they have to begin the head. The head is an area that contains as much anatomy as the whole from the neck down. And all that anatomy is in a very small box. And it's actually very complicated to understand. And when you dissect the head initially for the first time it doesn't seem to make any sense. You see the muscles of facial expression, which have wonderful names, very evocative names, but are every complicated. Everything really goes off the rails when you see the nerves inside the head, the so-called famous, or infamous, cranial nerves. There are 12 of these things. And this is one. This is a particularly complicated one. These are the names of this branch of this one cranial nerve, the trigeminal. There are a bunch of them. And they go through spaces. They have branches that do all kinds of things. They make no apparent sense. The best way to make sense of these things is, guess what, fish. And not only fish, but fish fossils, fish embryos, and fish DNA. And I like to think of it sort of like when my study as a paleontologist and as an anatomist forces me to look at humans in a different way. You might look at Einstein shown here as like all humans, like the pinnacle of creation. I tend to see Einstein just like all humans, as a crazy, kind of morphed up fish. [LAUGHTER] It's not far off. And particularly where the rubber hits the road here is in the head, this unbelievably complicated area, that we can make sense by understanding fish. So let's for a second compare Professor Einstein to the fish. He's on your left here. [LAUGHTER] In that head area, if you look at a human embryo a few weeks after conception what do you see? Here's the head. Just zoom in on it of an embryo. And you see the eye primordia developing here? They're paired, left and right. What you see are a series of four swellings, paired on each side, that develop underneath the eye. And these swellings are swellings. So they contain a lot of cells that are dividing very rapidly. And other cells are sort of migrating in there. And these swellings are separated by a cleft from one another. Well, if you look at any creature that has a head, just take a shark, what you find is sort of a same but different. That is you see, well, the shape is kind of different. But look at a shark embryo. What you have here is a head with the eye primordia. And look at the swellings. Paired swellings separated by clefts. You can ask the question, what do these cells do? Follow them. What do they become? Well, in a shark they become portions of the bones of the upper and lower jaw, and the bones that support the jaws and the gills, as well as some of the muscles, nerves, and arteries that supply all the stuff. Look at human. What happens? You follow these swellings. Well, the first one becomes portions of a lower jaw and two bones in our middle ear. The second one becomes sort of a throat bone that supports the muscles that help us in swallowing, and tongue movement, and so forth, portions of the skull, and a bone in the middle ear. Others become portions of our throat and voice box, as well as some of the muscles, and nerves, and bones that support all this stuff. To take a message of this as in an embryological sense, knowing fish, it tells you that some of the muscles, and nerves, and bones I'm using to talk to you right now, and some of the muscles, and nerves, and bones you're using to hear me with right now correspond to the gill structures in fish and sharks. Now, what's interesting about this story is it's not just based on this evidence. That is if you look at this diagram, what it implicitly says is that the ear bones of a human, or indeed any mammal, should relate to some of these bones that are the cartilage bones that exist in the jaws or the gills of fish, shark, and reptiles. And if you look at the fossil record that's exactly what you see. So here your ear would be out here. Here's the three bones, one, two, three. Here's the inner ear shown to your right. If you trace from fish to a human, what you see is one of these gill bones become smaller, and smaller, smaller, and smaller to become the stapes in our middle ear. Two of the bones were originally in the jaw of reptiles. They get smaller, and smaller, and smaller to become two bones in our middle ear. So just following what we see in the development we actually see in fossils the same transformation. The only way this makes sense is because of the shared evolutionary history that we have with fish, and reptiles, and other things. But why stop at fish? I mean, I'm biased to fish. I work on fish, and so forth. But why not think of other creatures? Well, it turns out if you start to look at the whole recipe that builds us you see a very general set of observations. One of the remarkable facts of biology is that life begins as a single cell, but each of us sitting around here are 2 trillion cells packed in a very precise way in our bodies. And the unfolding of that information to go from that single cell to the 2 trillion cells that are so precisely packed to make us comes about from a lot of information that's contained in the DNA of this egg, as well as many of the factors, molecules and so forth, that lie around them, and the environment that changes. We talk about this transition from this one cell shown at sort of pre-fertilization here to a whole body as bodybuilding. So to go from a structure like this to a structure like this, this complicated thing, involves the information contained in the DNA. It involves a great degree of the environmental interaction of these genes as their information unfolds. And of course a lot of steroids and hard work to get to this part. But if you begin to look at sort of the DNA recipe that builds bodies to some extent and look at some of the players there, a remarkable fact emerges. That is you can look at a fly, and you can find a series of genes that are active in particular regions of the body that are involved in sort of the proper placement of individual organs. You can trace these genes and ask the question, what are they doing in other creatures? And like in mammals, like humans shown here, they're actually underlying the basic development of the different regions of our own body, or at least of our vertebral column in particular ways. So what that means is that some of the basic toolkit that makes our bodies is actually present in other animals, and not just flies, but creatures as different as worms, and frogs, and fish, and so forth. So you can ask the question, well, who cares about our connection to the rest of life on our planet? And my answer to you would be something that is entirely trivial to a working scientist, but I think very sublime and very profound. That is if you look at the Nobel prizes in medicine or physiology, who have they gone to in the last 18 years? They've gone to people working on yeast, sea urchins, fruit flies, a sea slug. In fact, two Nobel prizes in the last seven years have gone to five people working on a little tiny worm the size of a comma on a piece of paper, Caenorhabditis elegans, which is telling us about how our cells die during development, and also providing important tools for understanding how our genes can be turned off in health and disease. It's providing insights, that little worm, that'll be useful for drug companies for various therapies for human disorders. I like to think that as we discover cures and treatments to everything that ails us, from Alzheimer's to various kinds of cancers, that that work will be originally derived from studies on worms, flies, yeast, and sea urchins. I cannot imagine a more powerful statement about the importance of our connection to rest of life on our planet than that. Thank you very much. [CLAPPING] Thank you. I do want to close actually with one other thing. And that is the coincidences that life presents us from time to time. You remember this diagram from Ashton Embry that shows his picture he took of that site that got us there? He sent it to us one year as a color photograph. We're sitting at the tiktaalik site one year, and Ted says, golly, I think I've seen this place before. Now, this is six years of traveling around all over the Arctic. That's the tiktaalik site right there. We ended up where it all began.