Wisconsin Public Television University Place  The Evolution of the Western Plains  Deborah Rook  9/18/13 UP919  cc >> Welcome, everyone, to Wednesday Nite at the Lab. I'm Tom Zinnen. I work here at the UW Madison Biotechnology Center. I also work for UW Extension Cooperative Extension, and on behalf of those folks and our other co-organizers, Wisconsin Public Television, the Wisconsin Alumni Association, and UW Madison Science Alliance, thanks again for coming to Wednesday Nite at the Lab. We do this every Wednesday night, 50 times a year, and it's your opportunity to participate in the life of the university, to share in the discovery here at this public land-grant research university. Tonight, it's my pleasure to be able to introduce to you Deborah Rook. She works in the Department of Geosciences here. She grew up northeastern Ohio and went to Case Western Reserve University where she got a degree in biology and evolutionary biology. Then she went to Ohio State University... Thank you. 

[LAUGHTER] And got a master's degree in evolution, ecology, and organismal biology. She says here that she has focused on mammalian paleontology and specifically on a bizarre group of North American mammals. So I'm hoping to hear what that is. I didn't know we had bizarre mammals in North America. Maybe they're all extinct. She's currently the chair of the Outreach and Education Committee here at UW Madison at the Crow Institute for the Study of Evolution. She's taught several classes, both at Ohio State University and here at UW Madison. And she lives here in Madison with her astronomer husband, Andrew, and her cat, Apricot, which gives me a chance to ask the question, who put the ape in apricot? Courage. Tonight's it's my pleasure to have Deborah here to talk about her work in Wyoming this summer and the paleontology of the grazer grassland. It's going to be a pretty interesting talk because there's not very many geologists who also study evolution. 

Please join me in welcoming Deborah to Wednesday Nite at the Lab. [APPLAUSE]  >> All right, thank you very much. As he said, I'm Deborah Rook, and I'm going to talk about the grazer grassland grapple. I may have spent a long time working on that title, just so you guys know. [LAUGHTER] And it's paleontological and geological arguments over the evolution of the western plains. So, western North America, why they look the way that they look. And just to give you a little bit more background about me, a little extension of what Tom just said, I do have a bachelor's degree from Case Western Reserve University, and I studied these guys. These are called notoungulates. They are really weird, all extinct, South American mammals that basically did something similar to what the Australian mammals have done where they just look like all of the normal animals that we have but they're just a little bit different. And so I studied those in my undergraduate work, but instead of actually studying those, I actually studied those. 

[LAUGHTER] Those are the teeth, the fossil teeth of the organisms I was working on. Using those, I was able to determine paleo diets. So, what they were actually eating during their lifetimes. But this is an important thing about who I am, is these teeth. Second, I did get a master's degree from Ohio State, and I'm sorry. [LAUGHTER] And I worked on a bizarre, completely extinct group from North America called the --, and they are these weird looking, kind of piggy, kind of, they weren't mean though. They were just eating potatoes. They look scary but they weren't scary. Like rodents of unusual size basically. And I studied the relationships of these guys, and, again, I studied those. 

So these are teeth from those mammals. So I think that this is important when we get to talking about my work that I'm doing now. I'm getting my PhD in the geoscience department. I am studying these which are, of course, not nearly bizarre nor extinct enough for what I'm used to, but I'm learning. And to do that, I'm actually going to be studying these. So, these are rocks and mammal teeth. So this is what I'm going to be talking about today is this connection between rocks and mammal teeth and what I am looking at try to figure that out. So, grazers versus grassland. This has been a battle that has been going on in the paleontological community for a really long time. And I'm going to give you a little background of the history of the debates and then also the history of the actual grasslands and grazers themselves. 

So, in the western United States you have grasslands with grazers on them. So, these are pronghorn antelope, bison, and it's an extensive part of western North America. This is actually the original, this is how far out the original bison went before European settlement. So, pretty extensive where these grazers were living. And that's one of the reasons that it's important. So, what is a grassland? Obviously, it has grass. You can see some of them have trees and some of them have fewer trees, but, generally speaking, large expanses of grass. And they have two main parts of their environments. You have tropical grasslands, like this beautiful picture here, where your temperatures are non-seasonal and are usually between 59 and 95 degrees. Doesn't that sound nice? This one is in Africa. 

And you get 20 to 60 inches of rain every year. And then you have temperate ones, which are more like what we have here in North America where you have huge seasonal swings. Winter being between 0 and 50 degrees Fahrenheit, and summer being 64 to 82. Of course, if you've ever been to the western plains in the summertime, you know that that 82 is just, I think that's a little low. [LAUGHTER] Having just come back from there, I think it's a little low. And you also see less rain in these areas than you do in the tropical ones. And another thing that's important for the grasslands is a lot of them have fire regimes. So, we know that when you start a fire in the west it kind of takes off like crazy. And one of the reasons that this happens and one of the reasons that the grasses can come back from these but houses don't come back nearly as easily as the grasslands do. Because the way that these organisms have evolved, they are used to these kinds of disturbances. 

And these kind of disturbances actually increase the nutrients in the soil. So, when this happens, all the grasslands are like, yeah. And they'll come back really quick afterward, which is also important to how they evolved, and I'll get to that later. The constituents of grasslands. So, grass, obviously. That's the big one. And then trees. Sometimes you see them interspersed, sometimes they have nice outlinings, but what's important and what a lot of people don't think about is that there's a whole bunch of other stuff that live in grasslands. So it's not just like grass all over the place and trees every so often. There's all sorts of other small, low-lying plant life. 

So, for instance, this is a grassland in Wyoming that I had the pleasure of driving by over the summer. And you can see lots of, there's plenty of grass but then there's also other bushes and small plants. And here's just another one just so you can get a sense of there are other plants, and that's kind of important when we're talking about grasslands and grazers because the thought is that grazers eat grass but there's other stuff to eat in the grasslands. So, what's a grazer? We have our lovely North American originals, horse and bison, and we have, we can't have Wisconsin the way that we do with all of our lovely dairy products and our agricultural center if it wasn't for these particular grazers. And then you also have the cool African ones, like the wildebeest and zebras. There's lots of grazers on all of the continents, but we're going to focus on North America. So, there's two main things about grazers that make them special. Their bodies. So, they have long legs. They're used to traveling long distances. 

Some of them can go very fast, like this guy, and they' built so that their main body is going to be dense and their legs are long and they're going to be really good at moving long distances. Whether quickly or slowly, they can get around around fairly easily. And the second thing that's really important about them, as you may have guessed from my initial slides, is their teeth. I'm going to throw some words at you, but I will explain them. So, the first one is lophodonty. I know. So, lophodonty means loafed teeth. We're really good like that. And this basically just means that you have these ridges on the teeth. So, these are all lophodont teeth. 

Don't worry about the names that are associated with them. It's just to show you that there's lots of ridges, and these ridges are important when you're trying to grind down grass because the grass has really coarse materials in it and also their cells are really more difficult to break down than, say, leaves. If you've ever played with grass, you can kind of figure that out. And so they have to, there's more tooth surface area to grind down on these things. The second word is hypsodonty. And that just means tall teeth. So, as you grind down on those loafs, you rub them down and eventually they're going to go away. And eventually you're going to continue to grind down your teeth, and if you have really short teeth, then eventually you're going to grind down your teeth and not be able to eat and, therefore, not survive anymore. And so, this is horses. They have very tall teeth. 

So hypsodonty usually comes after lophodonty because you need your teeth to be longer so that you can survive in these environments, eating this food in particular. And here are some more hypsodont teeth. So some of them are a little bit more extreme than others, but these are all grazers with hypsodont teeth. So, the modern connection between these organisms. This ecosystem is very connected, which is why it's sad that we've taken a lot of parts of the ecosystem away. But the grazers affect the grasslands in a number of ways. First of all, hooves are actually really good at stomping down forest saplings. Saplings are also easier to eat, so the grazers will actually go for the saplings first. Even though they are grazers, which means they eat grass, they're going to eat a sapling if it's there. And this goes back to that fire thing where these guys can just eat a whole bunch of stuff, and it's a lot more difficult for a forest environment to get kind of that foothold back into the area once the grasslands have started. 

Also, herding behavior creates a lot more nutrients for the grasslands because you have lots of animals all in one place. Yes. Going the other way, so coarse grasses wear down on the teeth, so that's why they have the tall teeth. And then you also, because you have these great expanses, these great long areas of open grassland, the herding behavior and the body plan become more necessary because to get from here all the way to the other side of the grassland where there's going to be more food for you, it's going to take a little bit of effort. And the body plans help them use as little energy as they can to get over those large distances. And the herding behavior is usually related to predators because it's all open and expansive and there's nowhere to hide. So, the evolutionary history comes in two parts. The evolutionary connections and then the natural history of the group. So, something that we know about grazers and grasslands, by the time that you get one of these things significantly in North America, this is really where the fight is, once you get one of them, the other one comes right along. These things are so interconnected that they co-evolve through time. 

And, as they are co-evolving, it just kind of gets worse and worse. The grasslands become more and more what you see today, and the grazers start to look more and more like the grazers that you see today. And it happens fairly quickly in the fossil record. So that's important. And, again, evolutionary connections are fairly similar. So herds are going to destroy forests, and the grasses, the story goes that the animals were there and they were eating the grasses so the grasses evolved to be more coarse and to have more of these particles inside so it will be more difficult for the mammals to evolve, or for the mammals to eat them. That's the story. And then, again, the herds increase the amount of nutrients in the area. In the other direction, that tooth wear, so the animals ate the grass so the grass go coarser and the coarser grass caused the animals to get bigger teeth, and then, of course, the bigger teeth leads to eating more grasses which makes the grass more coarse. Do you see how it kind of spirals out of control fairly quickly? And also, again, the openness kind of demands the body plan of these animals. 

What's interesting is that grasslands also feed back on themselves in their evolutionary history. They decrease the amount of carbon dioxide in the atmosphere around them. They can increase their own nutrients because of different things associated with them in the soil and also that fire regime thing. And they also decrease the humidity. All of these things are not particularly good for forest environments. So, the grasslands and the grazers are very well connected, and then the grasslands, once they really get a foothold, they can take off. The grazers are very helpful for that, but they are also keeping some of the forest things out themselves. So, natural history is just what were grasslands in the past. So, in Cenozoic history, I'm just going to give you a quick of what you're looking at. This is the last 65 million years. 

At the bottom, the very bottom is when the dinosaurs died out, and the top is where we are today. And during the Miocene, which was between, oops, oh goodness, sorry, which was between 24 million years ago and 5 million years ago, we have grasslands. They are grasslands. We have grazers. We know that there are grasslands and grazers, and towards the end of the Miocene you actually start seeing almost exactly the kinds of grasslands that we have today. The grass, the actual species and groups of grass that are living there are similar and the way that they photosynthesize is similar and that's the Miocene. So this is where people usually fight is in the Miocene, and we know that we've got grasslands and grazers. We just know. >> What are those large, horse-like things? >> You know, I don't know. I don't study the Miocene. 

I was going to show you why my stuff is so much cooler than this. [LAUGHTER] So, my question becomes, and also because of the work that I've done in the past, what was happening earlier? What was happening at the beginning of this? We know that these things are really well connected in the Miocene, but what was it like? So, in the Paleocene, this is what the west looked like. It was completely forested areas, all browsers, and just to let you know why I do this, that is a -- in the bottom left corner. So that's one of my weird North American mammals. And we know that this was what the ecosystem looked like. And then we start seeing this opening. And the grass, we don't actually see that much grass record at this time in the Paleocene and the Eocene. That's kind of artistic license in this picture. But we do know that the forests were actually opening up. And we can tell this by different chemical markers that the canopies, the tree canopies were opening. 

So we know that the forests were kind of spacing themselves out for whatever reason. But we don't have that kind of information about the grass from this time. So we're pretty sure there wasn't grass like this that early. And then as the Eocene progressed, you get more and more open, and eventually you start getting those grass fossils. So the big question and the big fight is who came first. Because if the grazers came first, then they started it all out and they started eating the grasses and then the grasses had to change. Or was it that the grasses came about and then the grazers started eating them and started the cycle that way? And this is, I'm not kidding, has been like a big fight for more than 50 years in the paleontological community. Lots of papers going back and forth basically just yelling at each other. [LAUGHTER] But something interesting that happened last year, newsflash, was that they found very early mammal dentitia. So mammal teeth that were looking a lot like grazer mammal teeth in the Eocene way before you saw any of the grass fossils. 

So, this paper specifically says grit not grass. It's probably not grass. Grass is probably not what was causing it, and the mammals totally came first. And this is pretty much where we are sitting now at this debate is that the mammals came first. So that's good, right, because I love mammals. And so, just a recap of the history. Grazers and grasslands are intimately connected, and grazing tooth changes happened before we got any expansive grasslands in North America. So, what now? That's where I come in. So this was the debate. This is what people have been talking about for a really long time. 

And my thing was this, we were looking at this picture, there's mammals, there's plants, people were working on different aspects of mammal physiology, different aspects of the plants, how everything is connected, but nobody seems to be looking at the dirt. And, of course, as Tom said, I am an evolutionary biologist who is now in a geoscience department, so looking at the dirt seemed like a good plan. And nobody had done this before. Nobody had looked at this stuff even though we know that soil is very important to plants, clearly, because they live in it, and these animals, once you start seeing the opening of the trees, you know that they're not eating off high branches of trees anymore so they must be eating lower to the ground. Now, whether this is eating grasses or all of those other plants that live in grasslands but live close to the ground, you're still going to be increasing the amount of dirt that you eat if you're eating closer to the ground than up in the trees. So, I was like, let's look at the dirt. And so this was the data, and this is what I actually do here. So, I'm doing preliminary sedimentology and stratigraphy. Those are lots of big words, I know. I will explain them in just a second. 

So, rocks. So, each of these little layers on here is a different strata. So that's where we get stratigraphy, and stratigraphy is just the changes of these rocks through time. And when you're looking at this, you see lots of different colors and all of the different colors are going to be different kinds of rocks and that's the sedimentology part. So we're looking at the kinds of rocks and the way that they change through time. So what you're actually looking at, because I'm going to go to a diagram of it in just a moment, on the bottom is going to be the oldest stuff, on the top is the newest stuff, and you're looking at deposition. So these rocks were laid down nice and evenly over time. And so this is the same thing except that instead of being, like where you have the little gaps, that's where time is. So this has just stretched everything out to fit into where it lays in time instead of just in the rock. And each of the different sections is a different kind of unit, and all the colors means different kinds of rocks. 

And so we have a lot of detailed information. I know a lot of them look pretty similar in color for this part, but these are just really nice representations of the data I'm looking at. And one quick thing, the way that we count these things up, the easiest and the most efficient way that we've figured out to count these things is to count them by gap bound packages. So, basically, what you're looking at right there, all of those units are connected to each other in time, and that means that there was deposition, those rocks were being laid down continuously. There was no time in there, there was no gap in time that we don't have from the rocks. This is only important because of the way that you'll see my graph later. And that's just used to count them, to count up the different kinds of rocks that we have. So, Macrostrat is the database that my advisor created, and this has lots of really cool geologic information. If you are at all interested in geology, you can click around and see what kind of rocks are in different places and all sorts of fun stuff like that. So that's a plug for the website Macrostrat.org, if anybody's interested. 

And this actually has the database where all of our information is coming from and where all my data came from. >> Can you access it without a license? >> Yes. Yes. Yeah. So, what's important is Macrostrat also has the types of sediment. So this is just a random sampling of the majority of the types of sediment that Macrostrat has within it. And because it has this data, I can use this data to do research. This is actually what I do. [LAUGHTER] And taking stuff from the database and creating a useable outcome that I can actually look at and have some sense of instead of just the numbers that are in this database. And so going to explain and show you a graph. 

So, geologic time is on the bottom. On the left-hand side is 65 million years ago, the end of the dinosaurs, and all the way on the right-hand side is today. And we're going to look at volcanic sediments. So, sediments that came out of volcanoes, that are somehow associated with volcanoes. Specifically, actually straight from the volcanoes and then also kind of mixed with other dirt. And what's interesting is that I went and I looked at this and I saw that there's this kind of trend in there, and, specifically, during the early middle Eocene, that's when we get that mammal stuff starts to really change. And that's also when we start to see the opening of those forests. So I thought that it was interesting that these volcanics were kind of associated with that. And so, from there, just to give you a sense, this is where those volcanic sediments are in the fossil record in North America during the Eocene. So this is the entirety of the Eocene, not just that one section but to give you a good sense that there was a lot of that going on in the west. 

A lot of where we have grasslands now, for instance. And so, that led to my hypothesis. My hypothesis is volcanoes. Basically, volcanoes are hugely destructive things. Even if there isn't a lava flow, there's still a lot of environmental changes that happen when volcanoes go off. And if we were seeing a huge uptick in the amount of volcanic sediment, it is possible that these things were affecting the organisms that were living in these areas and possibly further out depending on how big they are. And some really important things about volcanoes, specifically to what I'm doing, is dust. Like, all of that ash and dust gets really messy, kind of everywhere. And so this goes along with what I'm studying. They also increase the amount of CO2 in the atmosphere, which is interesting and has something to do with this, but I'm going to focus more on the dust stuff because I want to focus on the mammals. 

So the hypothesis goes like this. Dust is going to wear down on mammal teeth. So you're going to get those lophodonties because everything's rubbing against the tooth. So it's no longer the coarseness of the grass that's causing the tooth changes but actually the dust that's on the food. So it might be on grass or it might be on sage or it might be on trees. It could be on anything. You're going to start seeing these changes, and, again, it's going to lead to taller teeth because if anybody's ever been in a dust storm, like you get it in your mouth and you can feel it grinding down on your teeth. So, given enough of that, you will start wearing down your teeth, and again, so that you survive, you will have to get larger teeth, will have to evolve. Interestingly, this will affect all mammals. This will not just affect grazers. 

So it's not just the animals that are eating grass that will be affected by this. And this paper, as lovely as it is, talks about grazers, ungulates, and other mammals and rodents and bunnies. And that's great because that's exactly what I was saying that it will affect all mammals. On the grassland side of it, dust actually disturbs forests, so forests are, again, they seem kind of dainty almost. A dust storm will disturb a forest and the forest can be kind of destroyed, particularly by nearby volcanoes. And the ash and the dust also changes the chemical makeup of the soil. And this is one of those things that you never really think about but the changes are actually really, really bad for forests and really awesome for grasslands. So, basically, if you're going to have a bunch of dust and ash coming down, it is likely that you're going to destroy all of your forests and let it be just a nice place for some grasslands to move in. And then you also see the increase in CO2 also interacts with the grasslands. So, the hypothesis, singularly stated, is volcanic initiation of grassland and grazer co-evolutionary dynamics in the early Eocene of the western North America. 

So that is a big whoa. [LAUGHTER] Basically, that diagram that I showed you that has the grazers and the grasslands continuing to co-evolve and co-evolve out of control is actually started by a geologic process and not by the evolution of one of those organisms or the other. So, that takes me to the last section which is how do you test this. So, how do you test a paleontological or geological hypothesis? These time scales are way too great to do an experiment. It would be awesome if I could just close off a little grass area, put some mammals on there, and just watch them for five million years, but I can't do that. So, we have to go back to the fossil record. We have to go back to where it was actually happening already. And over the summer, in July and August, I went and looked at mammal teeth in Wyoming, and right there, doesn't that look like a lovely place to look for volcanics? We actually have a really nice area where we can find mammals before and after the volcanoes in that area turned on. So that was kind of what we're looking for. And the test, this is what I did on my summer vacation. 

I had the pleasure of working with the UW Geology Museum, which is another plug. If you guys have never been to the Geology Museum, it's over in Weeks Hall just on the other side of Union South from here, and is fantastic. So, you should go over there. They're just finishing up a brand new exhibit that's going to open next week. That's pretty exciting. So I went out with... >> What is it on? >> It's on biomarkers. So, early, early evolution of life, how we know that it was happening kinds of stuff. So I had the pleasure of going out with this group. This is actually three recent graduates from UW and three current undergraduates, a sophomore, a junior, and a senior, and Dave who's all the way on the left side who is a PhD who works in the museum and also used to be my advisor student. 

So he's my buddy. And we went out and we looked at rocks. And so this is what the field looks like, and I know that before I went and did this kind of stuff I had no idea what field work meant. And so I want to give you guys a sense of what's happening here. So, this is one of my rock units. So one of those single pieces from those stratigraphic columns that I showed you. This is just one of them. Each of those little things are actually just slight variations in the makeup of the sediment. Not big changes, just little ones. I know and you couldn't tell from looking at it. 

This is Emily for scale. She is my height. So it's a lot of rock to look through, and it's a lot of straight up. That is just as steep as it looks. So, we went out and we tried to find mammal teeth in this place. This was actually the main area that we worked in. This is Deb's Hollow. Like me. [LAUGHTER] We're really excited. So nobody's looked at these rocks in 50 years. 

Actually, literally, 50 years. And, of course, now having been out on those rocks for a couple of weeks, I know exactly why nobody has looked at these for 50 years. [LAUGHTER] They are not the most pleasant to play with. You can see a little bit in the middle ground there's kind of a grayish and blobby looking. That is the best mud crater that I've ever encountered. And we're up on top of this, and we actually have to climb down. I'll show you some pictures of us down in the hollow. But when it started raining, I was pretty sure we were all going to drowned down there because all of the sides of the canyon just completely turned straight to mud. And so, it was beautiful, all of us clawing our way out of the hollow, making sure that we could come back the next day, which we did. So, very messy couple of weeks. 

But I think that's how field work is supposed to work. I think that you're supposed to go, you're supposed to get really dirty and really hate the rocks you're looking at by the time that you're done. [LAUGHTER] So, the work itself was a lot of this. We did a lot of looking for specific areas where we can go back to in future years and kind of dig out. So, these are a bunch of my colleagues for scale. Kim, on the far right side, is my height. And the unit where we were actually finding the stuff coming out of, so where next summer I hope to climb up to and start taking large chunks out to look through stuff, is probably 15 feet up. So we were doing a lot of climbing straight up to find stuff. And this was why it was really useful to have very tall people and also my friend Kim there who is a climber, like a professional rock climber. That was really useful. 

I don't know what I'm going to do now that she's not at UW anymore because I need to find myself a new climber. >> How far from civilization were you? >> This site is actually probably 20 minutes outside of Dubois, Wyoming. So, not too far from some sort of civilization. It wasn't too bad because we got to camp in a nice little campground instead of having to camp in the mud, which would have been the other option. And so, again, a lot of looking down at the rocks trying to, you can see there's kind of all sorts of pebbles all over the ground. Those pebbles are all coming out of the same rock layer that the animals are coming out of. And, of course, you would be surprised by this perhaps, but fossilized mammal teeth look a lot like rocks. So we spent a lot of time, our heads down, looking for mammal teeth throughout this area. So, the way that we're going to test this, just as soon as I have a chance to get through all of my samples, is, this is Deb's Hollow again, slightly different angle so you can actually see what I'm talking about, is I'm going to be comparing fossils that we found in the lower to fossils that we found up top. So, the volcanic initiation actually occurred right where that gray flat area is. 

And we are going to work to find lower ones, to find mammals that are actually below the initiation entirely. But we were not able to do that this time. It's partially because we didn't have the right gear to get down there. This was already bad enough. We're going to compare those right after the initiation to ones that happened much, much later all the way at the top. And the benefit of this is that we actually should be able to see the same lineage of organisms. So, very closely related species going through this time period. And we know by looking at the rocks that there's actually, the volcanism is continuing to increase through this time. So, if I'm right, which I hope I'm right, so this discrepancy here, hopefully down at the bottom we will find either earlier mammal teeth or maybe lophodont teeth but not very evolutionarily changed from the original condition. Whereas up top, we should start getting taller and taller teeth if the volcanics are what's causing it in this area. 

Yeah?  >> Can you assume that there hasn't been enough earthquake activity there to upset you time scale? >> No. This is actually a really nice area. So, the question was, do we know that there aren't any earthquakes that are upsetting our time scale? This is a really nice area where since the Rockies were formed, this hasn't moved much. So, all of the changes that you see, all of the different where you see the changes in the actual outcrop where the rocks look different, it's all because of erosion coming down instead of tilting or anything like that. Yeah? >> You're talking about teeth length and taking a look at the structure of the teeth. Are you going to be looking at what they were eating, if there was any plaque or other kinds of material on the teeth to find out the characteristics of that? >> Right. So, the question was, am I going to be looking at what they were eating or other sorts of things about the teeth, the characteristics? That's the hope. I actually, because I'm in the last year of my PhD, this is kind of my main project for right now, but I would love to continue this work. And, actually, there are different techniques and analyses that you can use to look at specifically the teeth themselves and look at, basically, indentations and different marks that are on the top of the tooth. And I'm very interested to see what those look like in these organisms and through this time period because it's possible that we could see the volcanic signature in that kind of analysis on the teeth like that. 

So, hopefully someday I will be able to do that, but I have to finish my PhD first. Yeah? >> Where you find teeth you should be finding jaws, and where you find jaws you should be finding skeletons. If that's true, while you're out on your digs, who's looking at those and what are they looking for? >> So, mammal teeth are interesting because they evolve, they fossilize much better than the rest of the organism. So we actually find a lot of just teeth. And jaws and skulls and whatnot I will actually be looking at also myself. >> Would you mind finishing because I have to make an announcement. >> Oh, okay. [LAUGHTER] All right. Oh, well, I was almost done. I just wanted to thank you guys all for coming. 

I hope that you thought that was interesting, and there's a million people that I need to thank for all of the work that I've done here. [APPLAUSE]