How Ancient Primates crossed Oceans (ft. Dr. Christopher Beard)
Maria Losito: Welcome to Interview with a Biologist. I'm your host, Maria Losito, and I'm joined today by Doctor Christopher Beard, who is senior curator of vertebrate paleontology at KU’s Biodiversity Institute and Natural History Museum.
How are you doing today, Chris?
Christopher Beard: I'm pretty. Well. It's a little bit cold outside, but that's what you expect in late January.
Maria Losito: It's true, winter has finally arrived this year. Well, thank you for joining me through the cold. I appreciate that. Would you mind telling us about your research interests?
Christopher Beard: Yeah. So, Maria, throughout my career, one of the real foci of my research has been the origin of this big group called anthropoid primates. Anthropoid today are monkeys, apes and humans, and they're interesting to study because they're so intimately related to human origins. If you compare the skull of a monkey, for example, to the skull of a human, you're pretty hard pressed to find significant differences.
On the other hand, if you compare them to a skull of a primitive primate like a lemur. Those things have many features that remind us more of, say, dogs, than they do of a human skull. So it's an incredibly interesting thing to study. It's something that for a long time we knew very little about, and it entails not just anatomical changes as you go from a non-anthropoid to an anthropoid, but also biogeographic changes, because we know that anthropoid origins took place on a really dynamic global stage, and that's what this paper mainly is dealing with.
Maria Losito: Okay, that's very interesting. So, I know that that topic also informs one of the classes you teach here at KU. Would you mind telling us a little bit more about that class?
Christopher Beard: Yeah. So, yesterday actually was first day of classes here at KU, and I taught my first session of a course called Primate Evolution and the Fossil Record, which is really one of my favorite classes to teach at KU. Students get really interested in and engaged in it. What we do in that class is we really start from the very beginning of actually before the beginning of the primate fossil record, animals that are likely to be closely related to primates, but they're not exactly primates yet.
We start there; we work our way through the fossil record of primates right up until humans. I've also added a lab component to that course for the first time this year. It's a separate one credit hour lab component that gives students much more opportunity to engage in hands on learning activities. We one of the great aspects of KU is that we have our own fossil collection, and we have plenty of fossils that are relevant to this subject and this is one of the best ways to get students access to those specimens.
Maria Losito: Yeah, you had mentioned that we have one of the top fossil collections for colleges within the US. But for your particular area of study with old primates, what would you say is the oldest skull that that we have?
Christopher Beard: Well, that's an important question. Probably, the single most skull, in the KU vertebrate paleontology collection that is relevant to primate origins and primate evolution, is a skull from the San Juan Basin and northwestern New Mexico. This dates back to the Paleocene. So, this is the interval of Earth history, right after the dinosaurs have all died and the mammals are evolving like crazy.
We have the only skull of an animal called Palaechthon nacimienti. It is a mouthful, but this is actually one of the oldest, skulls of a group of what is called them proto primates, that were living in North America at that time. And in fact, just last year, a brand-new study of that skull was published in the Journal of Human Evolution. So, it's still it's a very timely specimen. It was found back in the 70s, but it's still giving us information today.
Maria Losito: What would you say drives you as a researcher?
Christopher Beard: Well, I'm really lucky to be a paleontologist because it combines a lot of things that are just inherently interesting to me. My earliest memories of childhood are being fascinated by animals. My grandfather had a farm, and he was one of those people who basically had his own menagerie of animals. He had pigs, he had cattle, he had chickens, he had a pet possum.
And as a young child, I was just fascinated by these animals. I thought that they were just interesting in their own right. But as I got a little bit older, my dad was in grad school studying biology, and he started telling me bedtime stories out of his textbooks about things like evolution and the concepts that these animals that I was already fascinated by could change through time.
I mean, that just blew my mind. And that idea has captured me ever since. And so that's one thing, this intellectual interest in animals and, and evolution, the reason that I got so interested in paleontology was that you can do this outdoors. You can actually do original field research to search for new fossils. And I've always been kind of oriented toward outdoor activities.
So that was important. And frankly, the thrill of discovery, because paleontology is still a science where you can literally go out, somewhere on the face of the planet. If you know what you're doing, you can bend over and pick up a specimen that nobody's ever seen before. It's scientifically unique, and you've discovered something really new. So, all of that together is what drives me.
Maria Losito: That's really fascinating. I know in Kansas, we used to be a large ocean back, I think, in the dinosaur era, and a little bit beyond and before that, and there's a lot of, limestone, and fossils within that limestone. I just know that you can just wander out and pick up the right rock and then boom, there's a fish skeleton in it, and it's ancient.
So it's just fascinating, how much is out there if you are just willing to look and explore.
Christopher Beard: Completely true. I mean, here in the United States, of course, scientists have been looking for fossils for somewhere around 150 years, maybe even a little bit more than that now. So, we've done a reasonably good job of documenting the fossil record of the United States at this point. Not to say that there isn't more to be learned, there certainly is, but I'll give you one example.
It's not Kansas, unfortunately. It's the adjacent state of Nebraska, but a couple of years ago, one of my graduate students and I, published a paper about a very, very strange primate called Ekgmowechashala which --everybody loves that name-- It's a Lakota Sioux name, because the first fossils of this animal were found on the Pine Ridge Reservation in South Dakota.
And so the scientists who found those fossils and recognized that they were early primates, they asked Lakota people, do you have a word for monkey? And in the Lakota language, they don't, because they never encountered any monkeys. But they said, okay, well, can you come up with something that would signify monkey in the Lakota language? And that was the answer.It translates more or less as Little Cat Man, which I think is a really interesting idea.
Anyway, Ekgmowechashala Fossils, we found we have some critical ones from Nebraska that tell us a lot about this. It's the last primate in North America before humans get here. So it's a really interesting story.
Maria Losito: I am so excited that there's so much more that we've been discovering that I've never heard about. You're making me want to go into paleontology.
You've recently published a paper titled “Across Ancient Oceans Eocene Dispersal Routes of Asian Terrestrial Mammals of Europe, Afro-Arabia and South America”, in a very broad way, what kind of scientific topics does that research touch on?
Christopher Beard: What we're really trying to address with this paper is a big problem. It's a bio geographical problem. The overall question that we have to answer is, how in the world did these early anthropoid primates, these little monkey like creatures, how did they wind up being distributed during the Eocene on very different landmasses? So we're talking about specifically southern Asia, Africa and also South America.
And the problem is pretty severe because if you go back in time to the Eocene, roughly 45 million years ago, the Earth's geography was not like it is today because of plate tectonics and continental drift. So, for example, in the Eocene, Africa was an island continent like Australia is today. It was far to the south of its current position, and it had not yet collided with Eurasia in the modern Middle East, like we know of today.
So these early monkey-like things, could not simply walk or, disperse in the normal way between Asia and Africa. That's the most obvious problem. And then you've got South America, which also, unlike today, was an island continent because the Panamanian isthmus was not connected directly to South America then. So even if you're a monkey in North America, and by the way, we don't know of any monkeys in North America, either living or extinct –
You couldn't get easily to South America. But in the Eocene, monkeys were in all of these places. So how did that happen? This paper really tries to integrate all the latest information we have from the fossil record with all of the information we have from plate tectonics about ancient geography and it's actually worse than that, because superimposed on this dynamic Earth moving around like a fleet of rubber ducks in a bathtub, you actually have sea level fluctuating, getting higher and lower through time, which kind of messes up the geography as well.
The climate is shifting, too. The Earth is incredibly dynamic at this time and somehow these early anthropoid primates are moving, making radical shifts around the planet, which probably impacts their evolution, because you can imagine if early monkeys, colonize Africa for the first time, that's virgin territory as a gigantic tropical continent that they don't previously exist in.
So, guess what? An adaptive radiation takes place. And maybe that adaptive radiation is intimately related to how anthropoid became anthropoid. So, it's many big questions, but it's basically an integrative approach to try to combine life science and earth science, to get at this one question.
Maria Losito: You had mentioned, I think it was adaptive radiation, could you break that down for us a little bit?
Christopher Beard: Yeah, so adaptive radiation, if you think about an evolutionary tree, you have a group of organisms that may be represented only by one, 2 or 3 species. And we know, by studying the fossil record and even by studying genomic data, that sometimes something triggers that little non diverse lineage to suddenly undergo rapid diversification. So one species suddenly multiplies and becomes 25.
We know for certain there are a couple of ways that that can happen. One is one is colonization of a new place which kind of releases them because there's nobody there that does what they do. And so suddenly they can diversify and fill lots of empty niche space. Another mechanism that can trigger adaptive radiation is something that we often call an anatomical innovation.
So, one of these, one of these, species basically builds a better mousetrap, and that allows them suddenly on the basis of this advantage to, to radiate evolutionarily, we know that this happened both in Africa and in South America. What we don't currently know is how critical were these early evolutionary radiations, to literally turn a non-anthropoid into an anthropoid in terms of anatomy, we're still working on that.
Maria Losito: Now that we have some groundwork laid down for what your research is, can you tell us what your research publication was really about?
Christopher Beard: So, it's actually very difficult to reconstruct what we can call paleo geographic maps of the world. All right. We know what the planet looks like today. We can look at Google Maps and have a great idea at a high level of precision. But if we turn the clock back 45 million years, it's not so easy to reconstruct what ancient geography looked like.
Why? Partly because the world itself is, is dynamic because of plate tectonics. So literally, the ground is shifting beneath your feet. I'll give you one great example; we've been working a lot in Turkey recently, and what we have found out literally by studying the fossil record of Turkey, is that 45 million years ago, Turkey, its geography was completely unlike what we know of today.
It was not connected to either Asia or Europe. It was its own-- let's call it a lost continent. Kind of like Atlantis, if you want to imagine something like that. Turkey- what is today, Anatolia and the adjacent Balkans, places like Bulgaria, Romania, modern countries like that. Together they formed a great big, landmass or possibly an island archipelago, depending on how high sea level was that was sitting in the middle of a gigantic, seaway.
That's like the forerunner of today's Mediterranean Sea. But it was much, much bigger. This seaway called Tethys ran all the way from the Atlantic Ocean and in the west to the Indian Ocean in the east. It was so you could sail, from Florida to Singapore, through this, Thetheon seaway. You would pass by this lost continent that we've named Balkanatolia, the Balkans and Anatolia.
And so that just gives you one hint of how different ancient geography can be and for our story about anthropoids, we're happy to be able to report that we did find the very first fossil anthropoid on Balkanatolia was published in 2023. So maybe Balkanatolia played a role in how these early monkeys were able to spread from Asia to Africa and to South America.
Maria Losito: I know with in your paper you mentioned a few different ways that animals are able to disperse-- one of them, I believe, is rafting, I think land bridges may have been another. Would you mind expanding on that?
Christopher Beard:
So a major goal of the paper, especially the Earth science part of it was to try to literally set the stage of how it was possible for these early monkeys to move around the planet? It's really hard to generate hypotheses, much less test hypotheses, if you literally don't know what paleo geography was like.
So, we went to a lot of effort to do that using, latest technologies, some, some software that was just recently released and a lot of fieldwork in various parts of the world to come up with what ancient geography was like. The upshot is that, the in order for these early monkeys to be able to move, to disperse from Asia, which is where we think that they first evolved to Africa and then proceeding on to South America, the only way that they could do that was by traversing these large, wide expanses of sea.
We tried to figure out what were the most efficient ways of moving from one landmass to the other based on the new paleo geography that we've determined. But even the even the shortest, hopscotching across open seaway is-- I mean, we're talking hundreds of kilometers that these little monkey-like things had to get across and we don't think they could swim that far. So we're really talking about this mechanism called rafting, which, I mean, a lot of people hear that monkeys on rafts are the way that these early primates got to Africa and South America, they say this, this sounds outlandish, and to some extent it does.
But here's the mechanism. You're a group of monkeys. Monkeys are famous for being very social primates. They generally live in troops. You're a group of monkeys you're living in, let's say, southern Asia, in the Eocene, 45 million years ago, the Eocene was a greenhouse world-- palm trees have been preserved in Alaska at that time--To give you an example, there was because of the greenhouse conditions, there were epic monsoons, gigantic, storms and things that caused massive flooding in rivers. We think that as a result of these gigantic floods, the animals that happened to be living along riverbanks, sometimes the flood would erode the riverbank. Now you've got an acre of land with a bunch of trees, maybe with a colony of monkeys in it that gets swept out to sea.
So that's the mechanism for how these so-called natural rafts get started. The Eocene was an ideal time to do it because of the greenhouse conditions and the epic storms, and monkeys, as opposed to, let's say, antelope were a great, group of mammals to, to get swept away, partly because they were quite small, partly because they were living in trees and partly because they were social.
Because remember, if you raft one monkey from Asia to Africa, okay, maybe that's interesting for the monkey, but you're not going to get a founding population. You have to get a whole substantial population there at one time.
Maria Losito: Okay, that's interesting because I know that we see evidence of rafting within our current population, I believe some sloths have occasionally been picked up by essentially vegetation that just gets swept up and away and then up on a different island within their mangrove. So, I know that there's some current ties to way back in the past,
Christopher Beard: You're absolutely right, Maria. In fact, it's even more interesting than that. There have been eyewitness accounts of this phenomenon, even, in the last several decades. There was a hurricane in the Caribbean, I want to say this was back in the 90s, and a former colleague of mine was a herpetologist in Pittsburgh, Pennsylvania. She was working in the Lesser Antilles, in the Caribbean.
She knew what kinds of iguanas lived on which islands in the Caribbean, and after one of these hurricanes went through, a species of iguana that did not live on that island was suddenly there. She asked local people what happened, and they said, oh, we saw it. One day, this flotsam and jetsam from the hurricane came in, and there were iguanas riding on that stuff, and they colonized the island and they're still there. Its a viable population. So, there's actually eyewitness accounts of this happening. It's rare, of course, but yeah, it's been seen.
Maria Losito: Yeah. Just amazing that, you know, there's so many touch points between history and now and its sort of a continuous cycle.
We've talked about these anthropoid monkeys. Just to sort of tie it in with the creatures of today. Would you mind telling us a little bit about what those monkeys were like, and then what sort of evolutionary ties they have to current animals?
Christopher Beard: Right, so today, monkeys come in two main flavors. There are the so-called Old-World monkeys. Think about baboons and macaques and things like that, and then there are the New-World monkeys, like the capuchin monkeys, the howler monkeys, the spider monkeys, animals that live in the Amazon basin today. So those two big evolutionary radiations of monkeys, and, you know, for true fans of evolutionary biology, please forgive me for using a generic term like monkey, because monkeys are not what we call monophyletic, because they exclude this group called apes and humans that we belong to.
So, apes and humans are more closely related in an evolutionary sense to Old World monkeys than Old World monkeys are to New World monkeys. So, when I when I say monkeys, it's I'm kind of committing a faux pas But, what were these early monkeys like? The earliest ones that colonized Africa were not, strictly speaking, Old World monkeys.
What they were is, if you can imagine, an evolutionary tree, they filled that space between non monkeys and monkeys. So. And we're still piecing together how monkey like were they. Did they have 90% of monkey features? Did they have 20% of monkey features? We know that they were phylogenetically related to monkeys. We also know that they were not Old-World monkeys.
They were. We can call them stem anthropoids. So that's the correct term. So, these were, biologically, what did they look like? Probably a lot like a monkey. If we just saw one at a zoo, we would probably all agree. Oh, yeah, that's a monkey. But it would be a very small monkey. Most of these guys weighed somewhere in the range of between 100 and 500g.
A big one would weigh a pound. So that's a small animal. They were totally arboreal, very reluctant to come to the ground because that's, you know, you lose the Darwinian game if you're a little tasty morsel like that, and you wind up on the ground. What did they eat? They ate fruit, they ate a lot of insects and things like that.
They were little arboreal, very active. Kind of. When you're that small, you're kind of. You've kind of got a caffeinated physiology. So that I think is kind of painting a picture of what these things were like. Now, by the time the earliest monkey-like creatures got to South America, which happened not long after they got to Africa, by the way.
But the ones that got to South America are already full-blown anthropoids. They already have all of those features and in fact, some of them are going to be basically ancestors of the living South American monkey radiation. But again, they're tiny, totally arboreal and eating fruits and things like that.
Maria Losito: Awesome. Thank you for painting that picture for us. What kind of methods do you utilize to find your research results?
Christopher Beard: Well, this paper uses a lot of different methods because it's an attempt to integrate paleontological, i.e. biological data with geological data. So, geologists are using very different methods than the biologists are. Geologists are mainly concerned with methods related to geochronology. How old are these fossils? At what point in time did this continent collide with that one?
And so those methods include things like radiometric dating using unstable isotopes of different elements, potassium-argon is one example. There's also a method called paleomagnetic reversal stratigraphy, which depends on the Earth's magnetic field literally flip flopping through time because of dynamics in the core of the Earth. So those are the kinds of methods that the geologists were using in addition to some recently released software, which just basically enhances data analysis.
The biological data that we're using are the fossils themselves and then our phylogenetic analysis of where these fossils fit on evolutionary trees. Again, today, modern phylogenetic analyzes rely on fairly sophisticated software to try to understand as well as we can what the evolutionary tree looks like.
Maria Losito: During your research, what kind of findings did you have and then what do those findings mean for further research?
Christopher Beard: Well, we've definitely established that these early monkey-like creatures had to raft across open seas. A lot of biogeographers hate that idea because it's kind of like the deus ex machina of biogeography. I mean, it's kind of like saying, ‘well, okay, maybe they got on an Airbus, and they and they landed in Africa or something’ but literally what we know about Earth history means that this is the only way. It's the only mechanism that these organisms could move.
What we found that has broader implications, is that the monkey-like creatures were not the only animals to do this at that time. There are a number of rodents in particular, the living rodents of Africa and South America- think about things like chinchillas and guinea pigs, those animals may have been on the same rafts as the monkeys. From everything we can tell, the fossil record indicates that, the genomic data indicates the same thing. So, this rafting phenomenon is broader than we originally thought.
Maria Losito: For the everyday person, why is it important that we keep doing this kind of research?
Christopher Beard: I think almost everybody has asked the question-- who am I? How do I fit into the rest of life on earth? Everybody wants to understand how things got to be the way they are today. I think that's just inherently interesting. This kind of research tries to answer that question.
Scientists are supposed to be people who are not concerned with broader issues. We're just looking at hard data and trying to analyze that, but I actually think that that understanding more about how humans fit into the evolutionary tapestry of life on Earth raises really significant ethical and philosophical issues. For example, the fact that humans are nested within this big primate radiation, for me at least, raises the issue of animal rights.
I mean, chimpanzees are our closest living relatives, gorillas farther away, etc.. Should we think about conferring special rights on some of our closest relatives because of our close evolutionary affinity? So that's one issue.
Another issue is the biodiversity crisis that we face right now. Many of our closest living relatives, especially the great apes, they're all endangered taxa. It's possible that our grandchildren would live on a planet where all of these species are extinct. And to me, that would be a real travesty.
I like to think about the fossil record, imagine that some lucky anthropologist in Central Africa found a surviving group of australopithecines left over from two, 3 million years ago--So suddenly we've found a living population of things that are even closer to us than chimpanzees. What would we do? Would we fill everything? -- Would we raise big fundraising appeals to try to preserve them and make sure that we could preserve our closest living relatives and possibly study them in order to understand our own history? Would we wage a genocidal war against them? I mean, I think that these are important issues that evolution actually implies about how we think about us and the rest of the planet.
Maria Losito: Thank you so much, Dr. Beard. You know, we really appreciate you coming and talking to us and giving us, you know, me. Just some really interesting things to think about.
Christopher Beard: It's my pleasure, Maria. I appreciate you being interested.
Maria Losito: Thank you for listening to Interview with a Biologist. You can check out the show notes for more information about Doctor Beard's work, as well as a link to the research paper discussed in today's episode. A full transcript of this episode will be available at biology.ku.edu.