Evolution of Human Behavior, Anatomy & Diet, Homo naledi & the Cave of Bones | John Hawks | #126
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John Hawks 4:48
South Africa we had a great field season this year and of course a lot of exciting work going to going on rising star and other sites. I've also been last week I moved my son into College. So we've got, you know, family stuff that's happening. We're getting ready to ramp up another school year teaching, teaching biology of mind again. And so we're, you know, sort of got these aspects of how we study the evolution of brains and minds behavior on my mind.
Yeah, I mean, that biology of mind, I took that course with you, you know, a decade ish ago. And that was, that was one of my favorite classes. That's great. Good. I don't I don't know if it's possible. But yeah, if there's any way that you could get those lectures up, I think people would love that.
Well, I think this year, I'm, I'm embarking on a shift to it. And the reason I was supposed to be on sabbatical. So one reason why I'm keeping things small is because it was unplanned that I've been teaching in the fall. But the other reason is that I really want to, to refocus, and to bring in some of what's going on with artificial intelligence, some of what's going on with machine learning and the way we work with neuroscience today, with machine learning. And then the evolution side, there's been tremendous changes in the last five to 10 years that, you know, that that I haven't been able to keep up with, because of the field work. So I'm sort of using it as a as a platform to, to renovate and to say, you know, how do we, how do we teach a course on the evolution of brain and behavior today?
Nick Jikomes 6:34
Yeah. And so are you back in Wisconsin right now? I am indeed. Yep. And how long were you in Africa?
John Hawks 6:41
This summer, six weeks in the spring? I was there for a couple of weeks as well. I'm usually in South Africa three or four months a year. Oh, wow.
Nick Jikomes 6:50
So that's primarily the rising star cave where the documentary was filmed?
John Hawks 6:55
Yeah, that's, that's our major field site. We also do work in the field at three or four other sites. We've got a new site that we're working on called the 105. site that has that has fossils we're working on now. And in some other sites, including malapa, the place where Australopithecus sediba was found. So yeah, well, that's I mean, that's, that's so cool. Like you get to you get to travel to all these places, and dig up the bones, and do field work and not, you know, just be, you know, just be doing the other stuff associated with research. Yeah. So, I mean, obviously, you guys are finding new stuff, like brand new species that that we're going to talk about, but like was that, you know, because I talked to Lee Berger, maybe about a year ago. And he was telling me how, for a long time, you know, I guess in the 90s. And the arts, the thinking that was fairly dominant in paleoanthropology was, essentially, that all of the major species of homo and other things had more or less been found, and there weren't a lot of gaps that were gonna get filled in, and that it was futile to be going around looking for new stuff. Was that the case? And and what sort of led led to the transformation in terms of why you guys are actually out there doing this now?
You know, I would say this is really true. You know, when I was a student, we sort of thought that we were filling in gaps, we thought that we knew the basic outline. This was not without reason, the fact is that much of what we had found at that point, looks like it could fit into a fairly simple picture. And particularly when we got to the evolution of our genus Homo, it looked like you sort of had a basic outline where our Genesis arose a little over 2 million years ago, it started out with larger brains than Australopithecus, which had come before and got bigger over time. And started out with biggest teeth that got smaller over time. And if you took those two trends, much of what we had found sort of fit into those two trends really well, based on the time that the fossils represented. So it kind of looked like we had the basic outline. And what we were doing was filling in a picture that wasn't very complicated. It took some new discovery trees that happened early in this century, to shake things up and to say, Oh, wait, we actually haven't surveyed the parts of the world where hominids lived. And as we look more widely, we're finding things we didn't expect to find. One of those was Homer floresiensis, the very small brain, small bodied hominin, from Flores that lived until the late Pleistocene limped within the last 100,000 years. We said, Wait, I didn't think there was supposed to be something that we hadn't done. Whoever that was this different from us. At that time, it was still possible to say, but it lived on an island, it's off on its own. Maybe it didn't make a big difference to anything else. Australopithecus sediba, which is 2 million years old, also factored into this factored in, because it was in a place where we looked really hard, the middle of the cradle of humankind World Heritage site at South Africa. And yet, it represented a lineage that we hadn't seen. And it was at the time and place that our Gen s homo arose. And so we said, we thought we knew this story. But actually, there's something here that that we didn't expect to find. Homeowner Leti was a big part of this, because when we found it in 2013, it immediately didn't fit in, it had a combination of features that we hadn't, you know that that combined features from very different kinds of things. And as we found out, it actually lived 250,000 years ago or so, it lives there when our species Homo sapiens had arisen. And yet, it was super different from us. So those kinds of discoveries have made us revisit what we thought we understood, there's a tree that includes some very different species that coexisted with each other to an extent that we hadn't appreciated. And in fact, many of the places where hominids may have lived in large numbers, places like most of central tropical Africa, places like most of South Asia, we actually haven't found fossil evidence in any large numbers. So we'd have no idea who lived there. And that's what's driving our exploration process. today. It's what's driving our new way of thinking about how the species may have evolved.
Yeah, how the species may have evolved. And I want to talk about the idea of species. And I think everyone has an intuitive idea, everyone walking around whether or not they're an anthropologist, or a scientist, or just, you know, your average Joe, obviously, there are different things, right? Like, we are not whales, we are not leopards. We're not chimpanzees. But as you get closer and closer in terms of relatedness, it becomes trickier and trickier to say, Well, are they different species? Are they not different species? You know, Neanderthals and modern humans? Will, you know, we'll talk about some of that stuff. And there's multiple reasons for this. I think, one, like just sort of the intellectual side, we need to have words and concepts to label things and talk about them. But also, you know, there's, there's sort of a human, like sociological sides of this. Because, you know, especially like in your field, right, when you dig up new bones, it's more exciting to find a new species than it is to find, you know, just another example of one that we found a bunch of. So there's these interesting tensions that happen, people talk about lumpers versus splitters. But I just want to ask you a basic question and get, like, your take on how you think about it, and maybe sketch out some of the major ways that many different people think about it. But what are species? And what defines whether or not two things are a distinct species?
It's a super question. That's right. It's one that anybody should ask. And my attitude about this has changed. Over the course of my career, I started out as really a lumber. And I was like, you know, humans today are pretty variable. We're a species that has large variations in body size, in body shape around the world. And we look around and we see people that look kind of different in different places that are all one species, that there's no reproductive barriers at all this preventing people from being able to reproduce with each other, other than the fact that they live far apart. So I look at species and I think, you know, a species can encompass a lot of variation. I'm a unique in a unique setting of being responsible for naming new things as species sometimes. And so I think really carefully about this. It's like, you know, how much variation does it take to call something different? We know that humans are a different species today than any other living organisms. Chimpanzees, bonobos are close relatives of ours. But their ancestors diverged from ours more than five or 6 million years ago. And a lot of evolution has happened. And they're pretty different from us. And we can't reproduce with each other. So we know they're different. Everything that we're looking at in the fossil record of humans and our relatives is closer than that. We're looking at species that diverged over the course of a million years to millionaire Is 3 million years. So how much does it take? I have been inspired a lot over the last couple of years by Darwin and his thinking about this. Because Darwin, really famously, a lot of people have criticized Darwin saying, he named his book On the Origin of Species. And he never actually explains what a species is. It's true, actually, Darwin sort of has this famous line, where he says, when it comes to species, it's this is not a literal, quote, but But it's it has the gist of it. When it comes to species, I find the best thing to do is to trust people who know the group. They'll tell me what easy's are, it's because there are these Blurred Lines. And of course, that was exactly Darwin's point. If Darwin's theory was correct, there should be blurred lines all over the place. Because species are evolving one into another, and have emerged from common ancestors, they must have been able to reproduce in the past. And if they can't reproduce today, that must have happened gradually. So we should find all kinds of species that blur the lines that reproduce with each other. And in fact, over the last decade or so it's become apparent that that's exactly what we see all over the world. People used to talk about horses and donkeys being different species, because their offspring mules if it's a mare, and, and they are a jackass that are the parents, or whinnies, if it's the other way, right? If it's a female donkey and a stallion, those are mules and whinnies and they don't reproduce, they're not fertile. Right. And everybody understands Oh, yeah, mules. That's what a species is, when you have these two different parents and their, their offspring are not fertile. But today, we appreciate that in horse evolution, there are lots of times that zebras and the different species of zebras and Somali wild asses and all of these different species interbred in the past, and that interbreeding was part of their evolutionary trajectory, that we're seeing this all over the tree of life, that we've got reproduction between things that have long evolutionary histories. And that's important to their, to what happens to them to their evolutionary fate. Species, Darwin said, The most important thing about them, the thing that I carry away from Darwin is that the reason why we don't see a continuous range of intermediates between them is because of extinction. Species are created by the extinction of the things that were between them. And when I look at the fossil record of hominids, I think about that really seriously? Like, why is it that humans are different from our fossil relatives? Because the things that were between them are gone. And of course, now, all of the fossil hominids are gone, right? We're the only survivor of our lineage, right? Why is it that we're different from chimps, because everything that was between us is gone. That has a functional consequence for humans and chimps, we cannot reproduce today. We have inter sterility between our populations. That may have been true of many species of hominids in the past may have been inter sterile. But they may not have been, what they were was different because they had evolutionary histories that some of them survived, and the intermediates come extinct. So when we're looking at the fossil record of hominids, and I'm asking what's a species? What I'm trying to do is identify aspects of variation that reflect an evolutionary history. I'm looking for the number of changes and the magnitude of changes that reflect some degree of history has has unfolded. At the border lines, this becomes hard with Neanderthals and African ancestors of humans. We know that those populations came together, that today, everybody in the world has some ancestors that are Neanderthal, and most of our ancestors are from African populations that lived at the same time. And when we look at meandered hauls, we know that they had a history of repeated crossings with African populations. We can see the signs and Neandertal genetics, that they were getting more and more genetic input from Africa. So I look at Neanderthals today. And I say, I think that they're human, that they're part of the same species. uses as all of us today, because there's this repeated interbreeding that's linking their fates. But many other anthropologists look at them and say, Yeah, but they became pretty different. And their fate had its own pathway. And they're gone now. And so Neandertals RSP sees, that's where we really have differences, where it's like, what happened to them over time, what happened to the intermediates, and did the interbreeding between them didn't make a big difference to their pathway to their fate.
I see. So, so sort of the standard thing that you often hear in terms of a definition or reading a textbook is this idea of, if two individuals can meet and produce fertile offspring that can go on to mate themselves to produce offspring themselves, then those are the same species. If they can't do that, then they clearly are distinct species, what you're saying. And what Darwin is saying is, yes, those things are true. If you can't produce fertile offspring, you are distinct species. But if you just rewind the evolutionary clock and look at what happened, at some point, it must have been true that the things that today can't produce fertile offspring together, were part of populations that once could. Yeah. And there's no right, there's no clean cut way that we can just look and say that, you know, may 24 70,000 years ago that was that was the day, there are literally these these blurry lines. Yeah,
it becomes a real issue with with conservation biology, right, we have an endangered species act, and that protects species that are threatened because of their small populations and habitat damage and all this stuff, right. And, and those species are defined by biologists. And increasingly, what biologists do is look at units in nature and say, um, these different populations, that maybe 50 years ago, we consider to be the same species. They actually have a evolutionary history that we can see today with their genetics is very long. And yes, when we put them in a zoo, they interbred, and we didn't appreciate that we should maybe have kept them separate. This is happening today with a Ranga tans. We today understand that there's two populations of orangutans on Sumatra, whose ancestors diverged more than 3 million years ago. Oh, wow. And one of them is much closer to Bornean orangutans. They their ancestors diverged a little over a million years ago. And the other one is farther. This new orangutan species was recognized in 2018. They call it a pongo tepidly ANSYS. And in zoos, Sumatran orangutans had been put together and had been interbreeding. And so we have hybrids of these different populations in zoos, we know that they can reproduce, right? Today, it's very crucial for us to understand this evolutionary history and to protect these populations because they have a long history. And in fact, there's some differences between them. Most primatologists are very comfortable with the fact we have three species of orangutans. But if we use the old interbreeding criterion, you'd look at those and say, Yeah, but even though they're different, even though there's these, you know, these deep histories, they can still interbreed. So, species today, we recognize that what the populations and their histories did not determine their fertility. The fertility can persist for a long time, between species that have been separated and evolution that have become different in lots of ways. In some lineages, fertility goes away really quickly, because the chromosomes change because there's faster evolution of the reproductive systems. But in other organisms, it doesn't. Right, we have species, the famous example of sturgeon and paddlefish, right, who've been separated for more than 200 million years, and still can produce hybrids.
Nick Jikomes 24:16
Yeah, and I suppose, correct me if I'm wrong, but I would suppose that in a case like that, where you've got a common ancestor that's so long ago, millions and millions of years, even though they can, in principle, if you force them to, in some way, produce fertile offspring out in the world, I'm guessing they probably don't just because they're either physically separated or because there are behavioral differences that make it functionally impossible that two of them will ever meet and meet
John Hawks 24:45
where species overlap in nature. We usually find that when they hybridize when they're forming high hybrids, those hybrids are limited to certain zones. Baboons are a great example of this today. We recognize six species of them They're regional, they live in different parts of Africa and Arabia. And in the past, when I was a student, we usually call them all one species. What changed is our understanding that where there's hybridization where we see hybrids, actually, those hybrids tend to be pretty distinct. And sometimes they reintegrate into one group or the other. And there's gene flow between them. Sometimes genes from one of those hybrids do succeed and propagate into the range of the other. But they don't form a continuous sort of gradient. There's a boundary, and the genes individually can sometimes cross the boundary and succeed. But it's not like a gradient of everything. With human populations, super different human populations, where we come into contact, we form a gradient. And the only places where you see big differences between what we identify as racial groups are places where they've all been brought recently, and are behaving differently because of social considerations. races and humans are social thing. And they don't have a long evolutionary history, where humans have lived for a long time, you see this continuous gradiation of variation. And that's really different from what you see with species that are different and hybridize with species, you see, actually, there's no big there's no long gradient, where they meet, there's hybrids, but those hybrids, you know, sort of have a fate of their own.
Nick Jikomes 26:36
And, yeah, one thing that's super interesting to think about too, is, you know, species come into being when there is a limit placed on gene flow between two populations. I remember learning, you know, evolutionary biology class back in the day, you learn about allopatric, versus sympatric speciation. And the first one is like really easy to think about, because it just means two groups are geographically separated. So you know, you can imagine, you know, there's an earthquake, and an island breaks off from the continent continent, it used to be a part of, and naturally over time, because you know, to a group of lizards can't cross the ocean, they're naturally going to become different, the ones on the island and the ones on the mainland, things like that. There's just this physical separation. sympatric is when somehow there is a limit to Gene flow, but the populations are geographically overlapping. And I'm not, I don't personally know of many examples of that. But it's interesting when I start to think about human beings. And in places like Africa, where you've got lots of lots of space, you've got lots of different populations, which are overlapping or adjacent to each other. And then you add the component that is very, very true of our genus where we have complex cognition and culture. And you can imagine that, even though there's not like physical separation, in the sense of one groups on an island off in the ocean, and one group is on the mainland, you could have cultural and behavioral traditions that start to evolve, that, you know, give a kind of barrier to Gene flow. And, you know, I'm just sort of thinking out loud here, as we talk about all of the different species in our genus and how we originated in Africa. But you know, I imagine when you guys look at the fossil record, in Africa, in particular, you know, for X number of million years, we had all of these different species and pseudo species or subspecies, whatever you want to call them. And there were probably, to some extent, physical barriers between some of those groups, other barriers between other groups that were not that were physically adjacent to each other, and everything in between, including some admixture.
John Hawks 28:43
Yeah, when we look across African mammals, because we know a lot about the biogeography of Africa, and we know today a lot about the genetics. So it gives us the dimension of history. Behind what today is biogeography, we see that there are close relatives that often live in the same place. In South Africa, there are Niala and kudu, right, those are relatively close relatives of antelopes, and they live in the same region. And they will usually concentrate on different resources or different micro habitats. So kudu are a little bit more friendly to steep hills and mountains. And, and the ALA a little less so. But they're ecologically pretty similar. And you say, Well, how did these become different from each other? Almost invariably, they've become different because they evolved in different places, and were successful and have come back into contact. Sometimes, the different environmental climate changes that have happened in the past, Pleistocene climate change was big in Africa as as as it was in Eurasia, but there it involved wet and dry cycles and the growth of forests the shrinking of forests at different times. Species seek refuge area of places where they are, you know, well ecologically suited when the climate sort of goes against them. And then they expand when the climate changes in a way that that's friendly to them. And that brings different populations into contact, if they've become adaptively different. And there's an advantage to sing separate, they can maintain separation, right? There's selection against hybrids. With hominins, the almost certainly that phenomenon was happening, almost certainly humans and our ancestors are living in different places, we become well adapted to different microclimates. In Africa, this involves disease as well as as sort of physical environment. So you're looking at places where you may have pathogens that are common there that you're resistant to that other nearby populations aren't. And that gives you an advantage in a region. All of those things probably made a difference. When we look at fossil hominids, we see that some of them that evolved and existed contemporaneously in the same place, seem to have really different ideas of what they're eating. So robust Australopithecus are good example, these giant tooth things that live at the same time as our ancestors jenis, homo. And they're probably ecologically differentiated, they're eating different things. With a species like Homo naledi, it's not eating different things from us, as far as we can tell. And so we're looking for other possible ecological differences. But the fact is that among today's mammals, close relatives sometimes do live near each other, and eat the same things and seem to have pretty similar ecology is because they're not locally limited on those things. And they've evolved in different places, but have come back into contact.
So, you know, we talked about this a little bit last, we talked about this last time, but it's worth bringing up again, just anchor the conversation. So I guess we'll, we'll spend much of our discussion here in Africa, so to speak. But I want to talk about, you know, what are so called anatomically modern humans? And can you just state again, clearly, where and when do do they first appear in the fossil record? Clearly?
Yeah. So what are you talking about modern humans, we're talking about everybody in the world today. And our fossil relatives, ancient skeletons of ancestors that have basically the same skull shape as today's people. Those arise basically within the last 120 130,000 years. earlier than that, there are populations or I should say, there are fossils within Africa, that have a lot of similarity to today's people and others that we call anatomically modern, but maybe have some features that are different. These are from places like the Omo cubish formation of southern Ethiopia, where we have a couple of fossils that are about 250,000 years old, from Djibouti, Allah hood in Morocco, a cave site where we have some fossils that are nearly 300,000 years old. Those are the most similar things that we found in the fossil record to us from that era. And yet, they're a little different from us. They're a lot more similar to today's people than any of their contemporaries, including Neandertals. In Europe, and in other parts of Eurasia, we're. So we're looking at the evolution of when we talk about modern humans, a population that seems to have gotten it start in Africa, that began sometime before 120 250,000 years ago, and came from ancestors that we can see that were maybe 300 to 250,000 years old.
Nick Jikomes 34:06
I see. So roughly speaking, modern humans are you know, they've been around for 120 150,000 years. In other words, if we could resurrect those bones and reanimate them, they would basically look just like us, and we wouldn't be able to tell any obvious differences if they were walking around. As far
John Hawks 34:24
as we know, yes. And they could always have something weird, like they could be blue, but probably skeletons would fit in the range of variation of what we see today.
I see. And then importantly, you said you know, going back even 300,000 years, the the fossils that we're calling humans or anatomically modern humans, more or less, they may have some differences, anatomically, when when you guys look at the bones and compare them to extant humans, but they're closer to what we see today than they were to any of their contemporaries living living. anywhere else in the globe that we know about.
Yeah, the kinds of things that we notice about their skeletons are things that an anthropologist gets really interested in, but nobody probably would notice. Yeah, you know, or they would fall in the range of people that you've seen, I would say that this is more or less true of Neandertals. Right. And with Neandertals, if you had a group of them, sort of that you were hanging out with, you might start to notice, hey, these don't look exactly like the other people around. But at a Neandertal individual, probably is not going to stand out as being real different looking for an undifferentiated crowd of people that don't like the kinds of things we see in the world.
Nick Jikomes 35:44
Yeah, if you're at a party, and all of a sudden a chimpanzee barges through the door, everyone's gonna go, Oh, my God, there's a chimp here. But if a group of Neandertals wearing clothes walked in, it might take you a minute, if you even noticed, they're, you know, they've got a little bit of a different build.
John Hawks 36:00
Yeah, yeah, exactly. The kinds of differences that we see between them and us are things that we don't see in today's people. Right. They're variations that don't occur today. But they're not variations that are huge, compared to what we see today. Right? They're variations that that the pattern tells us that these are a different group. But it's not like they're, you know, it's not like they're a different kind of creature.
Nick Jikomes 36:25
Yeah, and I mean, this is exactly I think what you were talking about where, you know, the lines are blurry in evolution, because things change gradually. Yeah. So, you know, our genus originated in Africa, there's a lot of super interesting variation that we've seen in Africa, in terms of the fossils, we dig up. And I know that, you know, this is something where there's been a lot of new discoveries that I probably don't even know about. But you know, for a long time, and you know, I can just in my own lifetime, I know that sort of the story has changed. But you know, people often talk about the out of Africa model, can you just summarize for people what the sort of standard picture of human evolution was, what the out of Africa model was, and what the what the average paleoanthropologists thought about that idea, you know, 1020 years ago, and then start to talk about how has that picture changed since that's
John Hawks 37:19
when I was a student. It was when this first out of Africa idea was was relatively new. And so I know pretty well what people thought before, right, which was we've got a deep fossil record in Eurasia. And our fossil record in Africa at that time was very limited. From the same time period.
Nick Jikomes 37:39
What went on? What year was this?
John Hawks 37:42
In 1990, floods, okay, right. So, so we had a lot of fossils from Europe in particular, but also a good number from Indonesia, from China, from from, you know, sort of more broadly across Eurasia. And they told us that there were hominids there more than a million years ago, that those hominins looked like things that we today call Homo erectus. And after that, they evolved to be something like Neanderthals. And at the end of Neandertal, existence, maybe 40,000 years ago, you see these modern people that are there in Eurasia. And for much of the history of anthropology that was interpreted in two ways. Some scientists said, this is just the evolutionary pathway. We started out as Neanderthals and we became modern humans. And that's, that's our evolution. Others said, you know, this change from Neandertals. to modern humans, this seems kind of sudden, we're not seeing much evidence of the in between stage between them. And this all happened kind of recently. I bet that modern humans came from somewhere else, and we just haven't found them yet. So the out of Africa idea, built on the increased record in Africa, which had produced a couple of these fossils, I was talking about the Omo cubish fossils, for instance, that said, maybe there's some early things in Africa that actually are much more like modern humans. We came from there. And the Neanderthals, maybe they don't have anything to do with us. Maybe they're separate. And genetics added to this starting in the 1980s. Genetics added in fundamentally two ways. The first way was an understanding that all of the people that we look at, especially in the 1980s all the people that genetic samples were coming from as geneticists began to study their variation. They saw that people around the world today seem really limited in our variation, it seems like we came from some very small number of people. When we talk about small numbers, it looked like 10,000. Maybe there were 10,000 people in the world at some point that seemed very small. And it seemed like a number that was not very consistent with humans living in large parts of the old world. It was like, oh, maybe humans came from some small place. The other part of it was an understanding that humans in Africa are more variable than humans anywhere else. So if you're going to identify that place, is Africa. And that began to align with what what we had found in the fossil record that, oh, there's early fossils in Africa that look kind of like modern humans. And genetically, it looks like Africa is a good source population. So this is now an idea. The out of Africa hypothesis, Neanderthals and Homo erectus and all these different groups that had once existed, had nothing to do with our later evolution. Humans in the world today came from some small source population, and that was African. Today, we know a lot more about this. And the story has gotten complicated. The fundamental idea that all of us have African ancestors And our populations as modern humans emerged in Africa is 100%. True. We know that this is true today. Where this has gotten complicated is on the two edges of it. The first edge is the African edge. Today, we appreciate that this small number 10,000 people is not a real number. It's a number that reflects the relationships and inbreeding in our ancestors, their structure in some way. And in fact, that population of ancestors that existed in Africa was large and diverse. In part, that change has come to light because geneticists began to get serious about sampling people in Africa. And they found out that what they had thought in the 1980s, and 90s, was subject to their, to their, at that stage, insufficient sampling of variation in Africa. So we today appreciate African populations today, having a heritage of variation from groups that were diverse, more than 100,000 years ago, and everybody that lives in the rest of the world whose traditional ancestry comes from your Asia, or Oceania, or other parts or the Americas, right everywhere else, where traditional populations lived. After 50,000 years ago, all those people came from one small group that lived sometime around 70,000 years, there was a very serious bottleneck. And that bottleneck is a bottleneck that was European, Asian Oceania, and American rights everywhere else in the world. Africa never went through that bottleneck, African populations retained variation. So when today you look at variation around the world, you say, well, Africans reflect our ancestry to a degree that reflects variation, other populations to all come from one small source. The other way that things got more complicated is we've got an ancient DNA from ancient groups, including the atolls. And we found that Oh, actually, these people contributed to some degree to later populations. That degree is small. It's something like 2% in the populations of the world that have the most Neanderthal ancestry. But it is a legacy that comes from these earlier populations from Eurasia. And in addition, we know today about the Denisovan populations is groups that we only have genetic samples from in the eastern part of Eurasia, that also contributed to different groups. So we know that we have a minority input from these very divergent ancient groups. And that most of our ancestry globally comes from an African groups that lived before 100,000 years ago, and that within Africa, indigenous peoples peoples who trace their heritage to Africa have more of the variation. And peoples who live other places have really restricted variation. It's because of this series of events.
So there's a certain amount of genetic variation in Africa for some amount of time in our genus Homo, because that's where we originated. some subset of those humans eventually leave Africa and sort of seed the rest of the planet. And so there is a real bottleneck there were a relatively small number of individuals. Yep, it's really make it out of Africa and have offspring that contribute to the future. As they do that there is some amount of interbreeding with things like Neanderthals and denisovans, as we're spreading within Africa. While that's happening. And before that's happening, how much do we do we have any evidence of interbreeding between modern humans and other species or subspecies that were in Africa the whole time?
Yeah. So finding ancient genomes from groups that were as different as Neanderthals sort of allow geneticists to understand the template, right? What does it look like when you mix with a very different group that led to the discovery, nice events, right? We'd have an ancient genome from Denisova cave that we identified and said, Oh, we've got interbreeding from this group. But in fact, if you look at populations that have the highest degree of Denisovan mixture, what we see today is not is that exactly that group, we see groups that are related to the Denisovan genome, and finding those segments of genome. That's a statistical process, we can now look at genomes and say, does an individual have input from a group that we haven't sampled yet, geneticists have done this in Africa. And they also have a limited number of ancient genomes in Africa, those ancient genomes are mostly less than 10,000 years old, and only a few of them or up to 20,000 years old. We don't have super ancient genomes from Africa yet. But the ones that we have do give us a picture of population structure before the events of the last few 1000 years. And so that lets us look a little further back and just give an idea of how diverse were groups before the spread of agriculture, the spread of pastoral herding and other kinds of things that have really caused a mixture of African populations in the last few 1000 years. As you look at those ancient genomes, and living people, we see signs that there was differentiation of African populations, that goes back further in time than 150,000 years. The today, largest genetic differences between populations in Africa are between Southern African hunting gathering peoples and the peoples of the rest of the continent. Those seem to go back a few 100,000 years, maybe two or 300,000 years. Before that, there were other groups, there was diversity in Africa, and African populations pre historically mixed with those groups. We see those echoes in the genomes of today's Africans. What we don't know is how separate those groups were, were the groups like Neanderthals, where they had a deep, deep history on their own, or are we looking at a structured population that just was always interbreeding but lasted for a long time? My colleague here at the University of Wisconsin, Aaron Ragsdale is, you know, has got a great analysis that suggests that African populations just have this deep structure, it goes back a million years. And it was because they were a large, diverse and successful population that had different regional groups. Other scientists, David Reich's group has looked at this and said, there were actually these really different branches. And they were as separated as Neanderthals were, and they survived until recently. And interbred, we don't know yet what the answer to this is, you know, as as someone who knows these methods and looks at it, I'm like, you know, what we really need is ancient genomes. Yeah, yeah. It's clear to me, and I think we'll have some but but for the moment, this question of how did the modern human population, right, how did it coalesce? How did it come together? 200,000 years ago, 300,000 years ago? The answer is we're not sure. It was complicated. We know that there was regional variation. There were different groups, we don't know is what the structure of those groups was, how widespread they were, where they lived, and, and what the interactions between them were like.
I mean, one thing that's kind of fascinating about the genomic stuff, and correct me if I'm wrong here. So before genomics was a thing before we could sequence genomes, you had to dig up bones and look at them. And that's, that's sort of what we had to go on. But it sounds like you know, genomics is in a place now where we've sequenced enough genomes and we've developed enough statistical tools and studied enough examples of stuff happening, different groups interbreeding and gene flow and interest, the evolution of species generally, that if you have an ancient genome, or any genome, you can act actually look at it. And if there was some kind of interbreeding between two different species, or something as different as Neanderthals and humans are nice events, you can actually see that in genomes before we've discovered that other species.
That's exactly right. Yeah, I could say the other thing that I think people don't appreciate very much is, we used to have the idea. When I was a student, this idea was still around, that if you found a feature of a skull, or a tooth, or a bone, that was really distinct, unique, like, oh, this shaped thing I've never seen before. And you saw it in two things, that that was really strong evidence that those two things are connected. Like we kind of had the idea that looking at it today, right, I can say, we kind of have the idea that bones work like genes. And if you found something that was strange enough, it was a really clear science, that there was a connection. Today, we understand that there are no genes that relate in any straightforward way to features like this, that when we see something strange in a bone, and something strange and another bone, there's no genetic pathway that gets us from here to there. And so as a result, we as I sort of have a skepticism about what we understand from the fossil record today. We, we understand that fossil morphology that the morphology of today's humans, when there's a feature in your skull, that's different from mine, that difference may be the product of 20, or 50, or 100 different genes. And there's something like the central limit principle, when you're comparing all these different genes with each other, that it's very hard to predict the outcomes of combinations of things. So two things that look weird on two bones, probably are just two unique events, and not a direct connection. So genes are vastly better at finding the importance of small fractions of connection. When I today can talk about myself having 1.8% Neanderthal genetics, but that's a measurement that I could never make from morphology. If I'm going to talk about 1.8% morphology, I'm in lala land, because morphology is somehow relying on the combination of hundreds of different genes. And I can't measure 1.8% difference between with jeans I can. So it's given us a language that's enabled us to talk about the connections of things and the existence of groups based on small fractions of evidence that we could never have had with morphology. And that's given us a new I think way of thinking about evolution. We now today are thinking about the connections between things where they might only mix 5% of the time. But it might be really important at the time that that happened. And with morphology, it's made us much more agnostic. I look at a species like Homo naledi. And I say some of its features look like recent humans. And some of the features look like Australopithecus and some of them look like very ancient hominids. And is it meaningful? Should I interpret that as saying that there's a mixture of things? Not necessarily, right? It's more complicated than that.
Nick Jikomes 53:49
At the time, that our lineage was first migrating out of Africa, and in the early days of radiating outward, deeper into Europe, deeper into Asia and so forth. How many other species of Homo were they encountering? And what were what can you kind of give a survey of some of the the major ones?
John Hawks 54:09
Here's what we know. We know that they encountered Neanderthals and the Undertows time that these encounters were happening, were diverse Neandertals included populations that had a history that went back well, more than 100,000 years and maybe 200,000 from each other. So as they're hitting the animals, they're hitting groups that are as diverse as the Africans that they've evolved with. We've got ancient genomes from Neanderthals to show that they're very distinct lineages of them that had some interactions but not a ton, right? That were their retained distinctiveness. They lived in different places that probably had pretty different lives. When they reached South Asia, these migrants we don't know who they ran into We, they might have run into some group of Neanderthals that lived there, they might have run in the nice events at that stage. We know that when they entered into eastern parts of Asia, they met Denice events that lived there that were similar to the Altai Denisova population, the population whose bones we found it Denisova cave. But they also met other groups that were genetically related to Denisovans more than anybody else. But that had diverged from Denisovans 200,000 300,000. And or longer ago, those groups today, geneticists have taken to calling Denisovan because the one example that we have as closest to them is that it needs to have a three genome. So we say, well, these are Denisovans. But they're Denice events that are more different from each other than any living people in the world are from each other. They're these events that lived in very different places, right? The ones that we found their bones they live in, in places like the Altai Mountains in Tibet. These live in Southeast Asia in Indonesia, right, so they're living in different habitats. They've been separated for 300,000 years or more. In some cases, they were pretty different. By the time they reached the islands of Indonesia, they run into Island species that we've recognized today from their teeth and bones that were probably isolated at that time. Homo floresiensis on Flores is one of these homo Luzon insists on Luzon and the Philippines is one of the is there may have been others. Certainly there were hominins on Sulawesi, we've got their archaeology, but we haven't found their physical remains yet. So we don't know if this is yet another one of these groups, or if it is Denisovans, or who it was. Homo erectus. As we understand it continued to exist in Indonesia, on Java until well, after 100,000 years ago. We don't know if the emerging modern human populations ran into this population or not. But they were there close to that time. And it could well be that they ran into each other,
Nick Jikomes 57:29
how approximately how different was Homo erectus from those humans sake, compared to the Neanderthals?
John Hawks 57:39
It's not super clear. The Hmong erectus populations that they ran into the latest surviving ones that we have great cranial evidence from 100,000 years ago, they have brain sizes that are close to the modern human range up to around 1200 to 1300 cubic centimeters, so so they had evolved bigger brains. skeletally, we know very little about their postcranial skeleton. So we've got a couple of tibia and a femur. So I can't comment super well on how different their postcranial skeleton was, their skulls looked pretty different. When these skulls were discovered, some anthropologists called them tropical Neandertals. They imagined them as something like the Neandertals in Indonesia. And while that's not literally true, it maybe gives a flavor to the kind of anatomical difference we're talking about. They're certainly more different from us than Neandertals in a genetic sense. But how much more different is not super clear. Okay, so what have we gotten up to now in terms of populations and species? There's three of Denise events, there's any Undertows, which are complicated. There's multiples of those. And there's Homo floresiensis, Homer Luzon ANSYS. And there's a more erectus where you're probably right, we're talking about eight, and maybe more. And that's just Eurasia. In Africa, we do know that Homo naledi persisted until at least 250,000 years ago or so. We don't know whether it became extinct at that time, or whether there may have been other species that continue to exist. This evidence that we have about interbreeding and population structure that whose echoes remain in today's populations, suggests that some groups that were pretty different did persist until the late Pleistocene. So until after 100,000 years ago. I'd say if I looked at the world, at this time, let's say 70,000 years ago, when modern humans, that group is diversifying and spreading into Eurasia, and asked, Who is there in the world at that time? There's a really large number of very diverse populations of hominids, some of which probably share ancestors, most recently more than one and a half million years ago. Others of which, like the Neanderthals, and denisovans share ancestors like 700,000 years ago. And, and some of which are anatomically, Homo floresiensis, I want to let it really very different from us.
Yeah, so So 70,000 ish years ago, if you could, if you hit in a time machine and go back and just look around the world, you know, many people have had the experience of going to the zoo or something and looking at the chimpanzees, or the gorillas, or just monkeys or whatever. And even though they're obviously different from us, you know, I've seen many times my life, someone notices, you know, the skull shape of an infant, chimpanzee, or they just notice some aspect of their behavior. And they have this sort of moment of, you know, wow, like, we really are cousins of these things. And in a deep sense, if you went back on a time machine, 70,000 years ago, you would have seen things that were clearly different than you and me, and yet even more uncannily similar, that we're walking around on two legs, and we're talking about what probably what, millions of individuals in total and a half dozen or more distinct or quasi distinct species?
Yeah, very possibly. And I think actually, those interactions, right, we know some of them interbred. And so we know those interactions were, you know, the range of interbreeding and interactions of that kind between human groups, right, who speak different languages who have different cultures occupy a full range, right, between people who love each other have have the same kinds of interactions that we wish for our children, right, in any society, who integrate into each other's groups across what must have been language and other cultural barriers. Right. Those people, I genuinely believe I can't I don't have the time machine. But I, I believe that they did not see each other as different in that way. Right? The kinds of differences that a modern group as we classify them would have seen from a Neandertal group. Those differences, they only ones that matter are, if they spoke different languages had different cultures, different expectations, right? They were all hunting and gathering peoples, they were eating the same foods Neandertals were hunting who were cooking grain and packets. They were, you know, yeah, lives that were fundamentally similar. And where they met, in fact, they may not have noticed anatomical differences. It's totally possible that there were, you know, when they met each other, those encounters were between groups that were largely mixed. So that's one extreme, keeping in mind that interactions between human groups that involve mating also include violence and aggression and warfare, right and terrible things. And I imagine that many of these interactions did that as well. That we're not looking at, you know, Pollyanna of the past, right? This is their people. They're complicated. And both sides of these interactions saw themselves as as people. Yeah. And I don't think they perceive differences in that way. They also met species that probably had no language or rudimentary means of vocal communication, no Homo floresiensis, right, I don't imagine that when modern humans met Homo floresiensis, they thought, Oh, these are just like us. I imagined that they thought this is something very different. whether there was any kind of, you know, cross interaction, whether they shared cultural information, whether there could have been interbreeding. We don't know yet. We don't have any evidence that relates to it. But certainly, these are groups that are more different by far than humans are from Neanderthals. And those interactions may have been, you know, not between people who saw themselves as people.
Nick Jikomes 1:04:34
When, you know, these are all versions of humans that walk around on two feet. And they did a lot of walking because they made it all over the globe. When when, approximately when and where, and I'm assuming somewhere in Africa is the earliest evidence of species of Homo that were exclusively or largely bipedal. When does that come onto the scene?
John Hawks 1:05:00
by PETA ality is one of the first changes in our evolution. We've got great evidence of bipedal hominins that walk in a fundamentally human like way before 3.8 million years ago.
Nick Jikomes 1:05:12
Okay, wow, okay, pretty, pretty low that
John Hawks 1:05:14
goes way back. And we know to say way back, right? About a third of our evolution has happened by that time. So it took some time. And there were hominins that we identify as our close relatives like Ardipithecus that did not walk up, right, like as we do, that had a more more ability to be standing upright, but did not have the foot anatomy did not have the spine anatomy didn't have the pelvic anatomy that later hominins do. So it took some time. But this was actually one of the first big human changes was upright walking our genus Homo, the earliest evidence of it is about 2.8 million years old. And so you know, by about a million years, or maybe a little more, after bipedalism is well established, then we've got our Genesis and our Genesis, the earliest evidence of it I gotta tell you is not great. We've got a jawbone is the earliest fossil, we've got part of a an upper jaw, that's, that's about half million years younger than that. We have very little evidence about this. Until about 2 million years ago, 2 million years, the first evidence of Homo erectus is found actually in South Africa, where I work and and from their humble erectus becomes a pretty successful species, it spreads into Eurasia. And and we've got, oh, something different is going on.
Nick Jikomes 1:06:41
So I think that yeah, this is worth talking about a little bit. So not only did our lineage go out of Africa and radiate everywhere, Homo erectus didn't evolve. It also did the same thing. It sounds like,
John Hawks 1:06:53
yeah, yeah. After the rise of Homo erectus, and I'd say after the rise, and I'm gonna say, a little sort of addendum after that, right after the rise of erectus, this seems like a successful model. It seems like it combines a human like ability to travel long distances, with a little bit bigger brain than had occurred in any earlier hominin. And, and it's clear that they are relying on tools, they have smaller teeth than the most earlier hominins. These become hunting and gathering populations. And that uses space, and they begin to expand through space. And wherever they can adapt to the new ecology they get. By 1.8 million, we've got great evidence of them in Georgia, in in the sort of central Eurasia. In the after that by about 1.7 million years, we've got evidence for them and China, evidence for them in Indonesia shortly after that, so they're pretty successful they spread, and that they spread all over Africa. My slight exception to this is that we do have evidence that's earlier in Eurasia. That's stone tool evidence. Homo floresiensis, maybe maybe evolved from an earlier branch of hominids, it's really different from us. And so there's a suspicion that maybe it didn't evolve from the rectus may come from something earlier. We're now today very interested in the possibility that there are earlier hominids that emerged into Eurasia before erectus, but we haven't found in their physical remains yet. And I wouldn't be surprised when we do. I think we will actually. What remains question is who's going to be? Is it going to be some earlier member of Homo Argenis? Or could it be something else? And I don't know yet. stone tool evidence in the last few years has gotten way earlier than it used to be. Her earliest evidence is stone toolmaking is now 3.3 million years old. That's way before Argenis arises. And so we do have, I think, a reasonable sort of suspicion these days, that Australopithecus was more sophisticated than we've given it credit for that maybe we're going to find that there's an earlier expansion of hominids. And I think it's just a matter of time, I think we are going to find them.
Nick Jikomes 1:09:25
I mean, that does seem to be a general theme in the history of paleoanthropology. And also, even more generally that, in general, as we learn more and more and dig up more bones and discover more things and start inventing technologies to do genome sequencing and just get more information. The story of our evolution involves, you know, our particular modern lineage not being quite as unique as we used to think meaning that things that we thought were just in our lineage actually, well, they were in these older In the edges as well, to some extent at least,
John Hawks 1:10:02
yeah, we have this way of explaining things, which is, you know, in biology, we call this the just so story where I see that something happened. And I know that something else is exists. And so I say, of course, this happened because of this. And, of course, it's a good way of forming a hypothesis, right? And there's a reason why we do this in evolutionary biology. Because when we know a limited number of things, the thing that we should test first is the two things we know. It's not a bad way of approaching science. But it's a bad way of approximating reality. So it's, there's a real tendency for us to say that I know that these two things happened at around the same time. And so they're connected. And what happens again and again, is that oh, actually, evidence for this, I found at some other time, I found it earlier, I found a different place. And so now I know that they're not connected. So now I look for the next thing that might be connected is the scientific approach. But somehow this idea of a connection never goes away. So that that is a universal, I think in evolutionary biology, right? We have these things, and we're looking at them and we're saying these should be connected. Somehow, the expansion of humans should be connected to this volcanic eruption. Right. That's a that's a really common one, right? The Toba volcano eruption 74,000 years ago, huge major event. And 25 years ago, geologist said, this is the biggest eruption that ever happened. And modern humans diversified from Africa to brown that time, these have to be connected. It's taken 25 years knowing that they're not connected. Because the modern humans started diversifying first, before the eruption. To to say, Yeah, but this idea persists. And it's really tempting when you have limited information to do that.
One of the, so I'm interested in what so I'm interested in the evolution of diet. But I'm also just interested more generally in sort of, you've mentioned what sounded like common themes that that happened along all of these different human lineages as they were evolving. So even though they evolved, you know, there's distinctions between Neanderthals and our lineage and denisovans and Homo naledi. And like all of these, there were differences between them. But it sounds sounds like there are some general themes. One of them being like, you know, brains tended to get bigger over time. And maybe some got bigger than others, but they all tended to get bigger. And another one it sounds like is that our teeth change in characteristic ways compared to our non human ancestors? So what can what can you say about the themes in the evolution of our dental anatomy and structure? And what that means about it? Obviously, there's lots of diversity between human groups past and present in terms of what they eat. That's, that's one of I think the features of humans is our ability to sort of have different diets and adapt in that kind of way. But what are some themes in the evolution of teeth and diet that sort of hold true across the different branches of homo, that distinguish us from our deeper ancestors?
So great question. And it's probably the one area that would drive you crazy, more than most in human evolution. The reason is, because we used to have this very well we, I would say, in our field, in the 1950s and 60s, had a very rational idea that humans today have smaller teeth than our near ancestors like homeboy erectus, there has been a trend toward reducing teeth in the human lineage from those earlier relatives of ours. Also, there are relatives of ours Australopithecus that had big teeth, compared to ours big molar and premolar teeth especially. And a branch of those dominance we called robust Australopithecus at that time today, we call them Paranthropus had mega big teeth, and big teeth like you've never seen. The largest Paranthropus have second molars that are almost the diameter is certainly bigger than a nickel and almost the diameter recorder. So they had big teeth. And there was this really logical idea that you could kind of that the teeth are adaptive to the diet that they ate. So the robust hominids, were eating lots of vegetative vegetation, they were eating stuff that had low energy density, they were they were chewing on vegetables, like gorillas do. That the smaller teeth were characteristic of the smarter hominids that are hunting. They're eating lots of meat. That's a super logical idea. It was called the dietary hypothesis. And it was what you taught in the 1990s. Everybody knew for the robust hominids to eat all the vegetables, and almost should eat all the meat. And the evolution of Homo should be tied to meat eating. There are a couple of challenges for that hypothesis, right. One of them is that chimpanzees, which do hunt a little bit, pretty much eat vegetable stuff, have small teeth, their teeth are like humans, the teeth do not look like earlier hominids. In fact, the early hominids, Australopithecus. There's no other species of primates that seems to have this adaptation of having really big premolar and molar teeth. In not a giant body size. gorillas have big molar and premolar teeth, they eat lots of vegetables, but they're giant. And their teeth have these, these shearing crests on them, they look like scissor action to chop up vegetable material. The earlier hominids did not they have flat teeth look like they could just grind something up. So anthropologist knew that you couldn't explain this. And as with a gorilla, like diet, they must have been eating nuts, other kinds of hard things that were very difficult to, to break down and require these big teeth with large grinding areas. That was state of the art 1990s. The world has changed since then, in two important ways. One way, is a better appreciation of the diversity of hominids. We know today that there seem to be some robust hominids that have smaller teeth. We know that there are species of Homo that have big teeth, homeward. Rectus does have some individuals have super big teeth. But other species that don't have big brains, so don't seem to rely totally on meat eating, that have small teeth like Homo floresiensis, I said super small teeth. I'm going to lay a small teeth. So you've got this diversity within our Janus, the small teeth don't go along with the big brains, and don't seem to go along in a straightforward way with the great tools. And the earlier hominids. So you've got this diversity, you got Australopithecus sediba, that looks like Australopithecus in most respects, but it's got small teeth. And you've got some Paranthropus of small teeth. So you've got this sort of weird, things don't go together the way they should. The other thing that has happened is development of technologies that give us direct insight into what they ate. One of those technologies is microscopy that enables us to look at the wear on the teeth, and quantify it in terms of what foods actually are doing to the teeth.
Nick Jikomes 1:18:22
So if you spend a lifetime eating mostly nuts, versus mostly leaves versus mostly meat, where's the tea chopping
John Hawks 1:18:28
on the nuts, and this and the stripping the leaves and the eating the beef jerky, all these different signs, and in fact, robust hominins the ones with the biggest teeth have the greatest diversity of science. Some of them Boise AI and East Africa. They've got super smooth were on their teeth, it looks like they're eating plants like gorillas eat or something. They're not eating lots of nuts and hard to chew things in South Africa they are holo kind is the reading lots of different things. But none of them look like they're especially focusing on meat or something like that. stable isotopes in the teeth also tell us what where their foods are coming from. And they're telling us that actually, all these hominins seem to eat kind of the same ratio, different foods. There are outliers. Neandertals eat a lot of meat. Compared to vegetable material, we can tell that from their trophic level from stable isotopes of nitrogen in fact, but within Africa looks like most hominids eat kind of the same composition of foods. Except this Boise i The big, the big toothed one.
Nick Jikomes 1:19:45
What what is that combination?
John Hawks 1:19:47
It looks like about 25 to 30% from sea for plants, warm season grasses, and something like 75% from cold season grasses and forbs So it's kind of like, it's kind of like an American diet. If you take out the corn. We get a lot of corn, right? A lot of our input is coming from Bayes, food, corn syrup and other kinds of things. But if we set that aside, it's kind of what we eat. And that's true. And in of all these homonyms, they're eating sort of the same composition of stuff. There's relatively little distinction between them in terms of what we find in their dental calculus. There's some interesting ones, Australopithecus sediba, seems to have cambium the inner bark of trees, fragments in their calculus. But aside from that, our evidence of what they ate does not reinforce the difference that we see in their teeth. It is not clear to us right now why that is.
Nick Jikomes 1:20:56
There's really some other there's just more work to be understood about how diet relates to the structure of the teeth, or I guess potentially another explanation is non food uses of teeth or something.
John Hawks 1:21:11
Some of this is totally possible. Yes. The reduction of teeth in the human lineage, right? Homeboy erectus has smaller teeth and Australopithecus. early members of like humble, early ancestors of Neanderthals have smaller, bigger teeth, and later Neandertals. Early humans in Africa have bigger teeth, and later humans, modern humans, right. So if we look at those things, I think it's fair to say that this is because of an increased extra oral processing of food. We are using tools and cooking foods, and that's relaxing selection on big teeth. And that's probably pretty safe.
And I suppose, I suppose a corollary of that if you're relaxing selection on big teeth, if you simply have relaxed selection on something, it's sort of free to vary in a number of ways. Yep. Yep.
Yeah, yes. And there's a balance, of course, which is that our teeth do other things besides, besides to. And while tool use is one of them, and important one that comes into play with Neandertals, we see lots of evidence of tool use with teeth being used as tools. The other one that that is important, that is undervalued, is is erupting, they have to come into your mouth. And that does create problems, if there's a malocclusion if they come into your mouth wrong, or if they're the wrong size to fit into the mouth that you have. These are problem things, and the reduction of third molars in our evolution. And the loss of third molars, among many people who will never develop them, probably is a consequence of reduction in jaw size. So you have this kind of whether there's selection, that saying don't make the teeth, these teeth or problems, or whether it's just that jaws are under selection to be smaller, and that's resulting in fewer teeth, because the lamina that leads to the tooth buds is reducing in size, whichever process it is, and that's the selection process versus neutral process. Both of them end up in the same place, which is that today, they're people who don't have third molars.
Nick Jikomes 1:23:27
A question that's a little bit random that's coming to mind today. Like I had I had braces when I was a teenager, because my teeth were not perfectly straight. And we spent a lot of money on braces. And this is a very common thing today. When you look at old skulls of ancient humans, how often do they have crooked teeth I'll just ask you that.
John Hawks 1:23:51
So when people are horrified by this malocclusion is something that came into popular nations largely with agriculture. When people became sedentary, we're eating agricultural foods, which which in large part involves cooking things into mash malocclusion comes in a major way before that people who are eating wild foods including today's hunting and gathering people's right who eat wild foods, they do not have malocclusions their teeth fit together perfectly. There are obviously some exceptions and people do cultural things to teeth today. Sometimes people file their teeth, they remove teeth, sometimes your mouth can is plastic, it can change your tooth positions just like braces are are exploiting plasticity. When you put forces on the teeth, your jaw will respond to those forces and the teeth positions will move. This happens with any cultural process that affects the teeth. But when we look at ancient humans and hominins that ate wild foods, their teeth fit together in the way that that nature intended. They don't have malocclusions.
Wow. And that's, I mean, I suppose that simply just do this, for biomechanical reasons,
are totally biomechanical, your ease, you know, think about it, but every time you bite on something, there's force that's being applied. And those four horses tend to correct the position of the teeth, they tend to put the teeth back where they belong. And a malocclusion can emerge if one of the cusps of your teeth gets worn down wrong. And now when you're biting down, it's actually putting pressure to force this tooth outwards or something like that, that causes malocclusion. So dentists are always telling you don't grind your teeth, it's going to cause a malocclusion. This is why, because your teeth, their form is actually well adapted to put them where they belong. It's a system that's not only programmed in advance, it relies upon the feedback that comes from chewing as your teeth are erupting. And if you have one tooth that's missing and the other tooth is erupting, it'll erupt too far. Because Because that process relies on the correction. That's the force that's being applied as erupts.
Nick Jikomes 1:26:17
And so I suppose the reason that that we start getting crooked teeth, after we become sedentary agriculturalists is not only do we start just eating different foods, we're making bridges and things like this that just have different physical properties. But when I think of modern modern humans like us today, like and I look at what we do with little babies, we give them soft things to drink and soft things to chew on. And I suppose that's naturally going to be a factor in their tooth development as well.
John Hawks 1:26:45
I'll tell you what, if you gave your kids now, people are going to watch the podcast and they're going to do this and I'm going to say I'm not a physician or a dentist and don't do what I'm telling you. But if you gave your children to toys that you give to dogs, like a car and made them work on it, their teeth would be straighter. The fact is that what why is it like when you look at people today in magazines who are smiling, you want to see their front teeth on the top. You don't want to see their front teeth on the bottom. Right. If they're giving you this smile, there's something wrong. That's happening. Right. That's like that's that's not right, right. That's not cosmetic. That's not what American orthodontists are aiming for. Why did this that's not a natural bite. A natural bite has the front teeth meeting in the middle because they actually were against each other. And you can actually sever things with your front teeth because they're wearing their right. We engineer with orange orthodontia today and overbite, the front teeth are in front of the bottom teeth. That Overbite is something that emerged in the course of history, largely from use of silverware. Using utensils to eat with and not clamping down with your teeth on things to to chew them this way actually causes your teeth to erupt in a different way. So much of what we recognize as as natural about our appearance, right? There's hardly anything that is as much of a social signal as smiling to somebody and showing them the fronts of your of your, of your top teeth. Right, is something that is actually highly cultural, and emerged because of the side effect of these cultural practices. What do
Nick Jikomes 1:28:47
you what do you hunter gatherer type people give their infants when their teeth are erupting? What do they give them to chew on?
John Hawks 1:28:55
Leather? Which is also I learned, right? What what my grandparents gave to their kids, right? Today, you have these sort of plastic friendly toys, but in fact, 100 years ago, leather, that's what they gave them. Wow.
Nick Jikomes 1:29:14
That's, that's fascinating. So I want to I want to get back to diet. So you've told us some fascinating things about diet? Are there any? We have technology now where we can basically just look with microscopes, we can look at wear and tear? Or we also to what extent are we able to you mentioned I think this to some degree, but how much precision do we have in telling from like little bits of stuff that are trapped in the enamel and things exactly what an ancient human was eating?
John Hawks 1:29:45
Well, there's two elements to that, right. One is can we identify it accurately? And that side of it is yeah, actually, people who study this do a remarkable job identifying tiny pieces of things. And we know things today like Neandertal was used medicinal plants like Yarrow that are not nutritionally valuable. And and you can because they've got the signs of that there, you can also identify the chemistry of smoke, and the chemistry of burned fat and things like that from calculus. So the sensitivity of the method is amazing. You find things, you know that this was in the mouth, it was ingested. The other side, however, is, do you find everything? Right? Are you getting a picture of a particular episode a moment? Are you getting some kind of average that tells you how what somebody ate over the course of their life on that score? It's very bad. We don't have any way of assessing, am I getting an average picture, and I'm getting something extreme. And again, it's something unusual. With some other approaches stable isotope sampling, for instance, you can actually get some of that, like today, the really cool stuff is being done by sectioning a tooth. And by doing isotopic and elemental analysis at a microscopic level, across its growth lines, which can give you information about a day that an individual lived. And you can say, when they were forming this layer of enamel, they were exposed to this element in their natural habitat. We can we know today for a few ancient hominids, exactly when they stopped being breastfed. We know for a couple of hominids that they were exposed to lead at a certain moment of their lives. For one, pre hominid for one ancient ape, we know the pattern of rainfall across the time that they develop their tooth. So there's amazing things that you can get from that kind of thing. And it does enable you for for a window of someone's life to talk about not just extremes, but some kind of average. But it's a limited amount of data you get from it, you're not getting what kind of plant you're getting. What was the input of this kind of carbon from a range of different plants?
Last question about diet, at least for our lineage. For the humans that were leaving Africa, or the ones that had recently left Africa, but still before the dawn of agriculture, what do we know about what they were eating?
We know actually quite a lot now. And that's a complicated time. It's complicated time, because it corresponds with the cultural changes that archaeologists identify as the later stone age. So before, let's say before, 50,000 years ago, most of the cultural evidence that we have from Africa is is aligned with a, a traditionally called middle Stone Age, middle Stone Age is more or less equivalent in terms of the tools that are being made, as Neandertal tools are in Europe. And later Stone Age involves a reduction of the size of tools and increasing the amount of complicated compound tools that are being made. People are using micro blades and putting them on projectiles and this kind of thing, they start using poison arrows, that kind of thing in Africa. By that time, the lifestyles that you're seeing among traditional African groups are pretty much what we see in ethnographic groups that anthropologists have studied for the last 100 years that are hunting and gathering groups and their diverse people living in different parts of Africa, eating different foods using specialized technologies to do it. So despite
Nick Jikomes 1:33:59
despite that diversity, are there any themes in terms of say, how the macronutrient composition the ratio of protein to carbs to fats differs from say, our ape relatives?
John Hawks 1:34:11
Yeah, we know a good bit now from ethnography and from from physiological measurements of what difference it makes hunting and gathering peoples, you know, that have been measured by anthropologists and Herman Ponsor has done amazing work on this. He's somebody that I would read his work and talk with him about it. Looking at hunting, gathering people's what's going on, with their with their diet with their energy intake. What's going on is that we use energy we right, human foragers use energy in short bursts with much greater intensity than other primates tend to. So we'll gather the same amount of food, but we do in a shorter time. And that makes our time budget very different from other species. It makes our pattern of work versus rest very different. And that has consequences for the way that people are gathering and for the foods, they're acquiring the macronutrient composition and that kind of thing. The major innovation and human foraging groups is an increased consumption of meat compared to other primates, including chimps and bonobos. So humans tend to work in shorter periods with more intensity. And that means that we're pulsing our energy in shorter units. And that gives us huge amounts of free time, we're using that free time socially. So that changes our energy budget. In terms of macronutrients, the biggest difference between human foragers and chimpanzees, bonobos, and gorillas certainly is the human intake of meat. And that's important in every hunting and gathering society. Also humans intake more, more honey, and more starchy foods or underground storage organs. Those vary a lot between groups, right? Look at different hunting gathering groups, those resources vary, but they're present in greater degrees, and almost all human groups compared to chimps and bonobos. So we're eating less leafy roughage type stuff, then chimps and bonobos do, we're eating more starchy sugar, and then meats. And that's sort of fundamental is shared among all the human foragers that anybody started anywhere.
Nick Jikomes 1:36:28
I want to spend probably the rest of the time talking about hormone miletti stuff for those listening. So I talked to Lee burger last year, who John works with. So if you want sort of more background on how that project got started, and where it is, and a lot of the a lot of the facts there. We talked about that. John, I would like you to kind of bring us up to speed on what's happened in the last year or two. And I believe I'll just name drop here, the the name of the documentary, I believe, is cave of bones on Netflix. It's really cool. So check it out, if you can. So give us a very concise summary of like, what is this humble, miletti discovery?
John Hawks 1:37:07
Yeah. So fundamentally, we've been working with homeowner Letty for the last decade. And initially, we found these bones in a cave. And they're in a very difficult to reach series of chambers in the cave, where I cannot actually physically go, our team is super skilled underground. Now, they include some of the most experienced underground caving specialists in the world, certainly in the southern hemisphere. But the key constraint is this very small passage, the chute that we call it, that is 18 centimeters, or seven and a half inches wide. So it's a tough place to get. We found the bones of abundant individuals, we reported when we found them and 2015. We reported 15 individuals, at least we know today that there are many more than that. And we found them in sort of a puzzling situation, where there are lots of bones of this species, and no bones from any other kind of animal in any in any numbers. And some of the skeletal remains of miletti. In this chamber were articulated, and some of them were mixed together with different bones from different individuals. Our dig was very small at that time. So we didn't know exactly what this meant. After that, we found their bones in another part of the cave place we call the left City Chamber, the first place called the dinaledi chamber, the list City Chamber had the skeleton of one individual with a few parts from a couple of others. And this skeleton was in a niche in the wall of the cave. And we were very puzzled by this, it was very clear that this species was able to use large parts of this cave system, these places are far apart underground. They're more than 120 metres from each other. And, and they were dark and scary. When I say scary, I mean that the passages are narrow, and they're hard to get to. And we know that they've been that way since the species was using the cave. So so the question is, what's going on? Right? From the beginning, we could rule out many reasons why the bones were there. We could rule out that carnivores had been involved in bringing the bodies there are no signs of that no evidence of carnivore activity on the bones. And that's pretty obvious when it's true, right? Yeah, yeah, exactly. You know, there can when you have one bone at carnivore bytemark, you might, you know, be be subtle, but with whole skeletons and this sort of thing it was, you could say no, there's no carnivores doing this. It would be the weirdest carnivore in the world that only preyed on humans, right. So, so there's something very strange about it. At the same time, we could show that water had not carried the bodies there. The sedimentology of the cave was inconsistent with having been formed by water washing into the cave or anything like that. So we can say, you know, it sort of looks like the lady got themselves there. Our hypothesis was maybe they're depositing bodies, maybe they're bringing bodies in the cave and, and dumping them. And this is some kind of mortuary space. That was a little bit controversial. Right? Other archaeologists looked at that and said, Well, we've never seen this with anything like a creature that has this brain size before their brains are a third the size of today's humans. We are skeptical when we see Neandertals doing this, you know, we think that this is something that's very cultural, it's very hard to identify. And, and to be quite honest, we'd be happier if it was carnivores, we got a lot of that. Over the past five years, our team has been working to expand our knowledge of the dinaledi part of this cave. And we've have found a number of things, we found parts of bodies, a skull of a child, in one case, that are 40 meters further than the shoot places where they couldn't get unless somebody took them there. And so that's part of what you know, sort of factoring into our thinking. But in particular, in 2017, our team found a bone concentration and brought it out of the cave. They packed it into caving bags, wrapped it in plaster, plaster, jacketed it like a dinosaur bone, and brought it out of the cave. And we're studying scans of that now. And the scans show us that there's a body inside of it, and this body appears to have been buried. And in a second excavation area, and 2018, we uncovered bone, a bone concentration that included many parts of one skeleton in what seemed like an anatomical order, we stopped and left that there began to study it, we think that this is also a burial. We think that holes were dug and bodies were placed in them. In one sense, that's not super different, right? We have already said, we think that the lady is using this as some kind of mortuary space. And that's why the bones are there. But in another sense, this is a step more complicated, did, we're saying that nobody was digging holes and burying bodies. And that implies that there was something very unique and special about this space to them that they were returning to and using it, that it was part of some kind of cultural activity. And so that's what the the documentary of the cave of bones is describing. My book with Lee cave of bones is also sort of describing these discoveries. But it's what right now is engaging us right, trying to understand what it means for another species like this, to have a culture and what other signs of it we might recognize.
Nick Jikomes 1:43:06
So if all of this is true, if if they do have a culture that includes going to a cave system like this, on purpose, burying the dead, and all of the things that would entail in terms of their minimum cognitive repertoire required to do all those things. Have you seen indications of a fire? Because they would have needed to light the way somehow? And what does that look like? And be? I would imagine it's plausible. I mean, if they were truly using these as burials, they truly had a conception of life and death in the sort of modern sense, I guess. I would imagine that they would have done things to mark the cave, or do things in the cave, other than merely cover up the dead bodies. Any evidence of that type of thing?
John Hawks 1:43:58
Yeah. So I'll start with the second one. First, we have in the dinaledi chamber, a couple of areas that we think are engraved, that have lines on the wall of the cave, that seem to form patterns, where we have described those in a manuscript, and we now have a team that is investigating what they can say about them. It is possible that these are intentional that there's a sort of pattern that's been made this marking a space, the markings that we see the patterns appear to be geometric, right in the sense of their lines intersect with each other, their shapes like triangles and ladders. And maybe that's something that they're expressing. But that's all we can say at this stage, right? We're not looking at Lascaux with horses or something like that. We're looking at lions that seem like they're made
Nick Jikomes 1:44:54
relatively simple geometric patterns. Would you say it's conclusive or that they're strong evidence that They are of human are that they were home on miletti Put those there? Or is that still controvert they're
John Hawks 1:45:06
in a space where we only have home on the ladies remains. And so that you know puts the first hypothesis is that no it put them there. The we have no evidence for any other species, including recent humans having been in that space. And we have a list of all the people that we know of that have been in that chamber so so we can say, this is not a trivial space for humans to have been in, we have no evidence that humans were there. And what we have is abundant evidence that melody was there. So that's our hypothesis. That being said, working with evidence of this kind is very challenging. It's not like a bone where you'd have some sort of chemical test you can do. The dating of cave art, the placing of it with ancient populations of any kind, relies on a lot of luck, you have to have natural cave changes that leave isotopic signatures that you can test and study. And we don't know if we're going to have that we have some of the best experts in the world on the team who are going to find out. At the moment, all I can say is I've got lines on the wall of a cave, that are really interesting, that are over bodies of this ancient species. And it seems like it's not a coincidence. But yeah,
Nick Jikomes 1:46:30
that makes perfect sense. The last thing I want to ask you about that, I mean, super excited I saw the the cable bones documentary, super exciting, super intriguing. It certainly does, it's hard to imagine how else something like that would have gotten there. And this was part of the documentary where, you know, I wasn't sure how much of this is the filmmakers, doing things with out having full expertise, or whatever. But there's this part where they kind of show you pictures of these engravings. And they sure do look like something, something like a human being probably made. But then it showed pictures of what looked like basically the same types of things in completely different parts of the world that were apparently made by our lineage or Neanderthals. So is that part? How true is that? What can you tell us about that?
John Hawks 1:47:18
It's absolutely true, that there are engraving all over the world that have this kind of character to them, that have intersecting lines that make basic geometric shapes. And, you know, we have colleagues who are coming at this from a neuroscience or psychology point of view, who suggest this is maybe fundamental, maybe there's something about our visual processing that makes these kinds of things really salient to our nervous system, so that we make them so that, you know, there's, you know, doesn't have to be a subtle communication across these places. It's just saying there's something about the human brain that these kinds of shapes are, you know, they draw attention to themselves for us. I think it's plausible, or certainly it's true, we see these shapes again, and again. I also I'm known in our team as, as the skeptic who says, If you're going to make something out of lions, it's going to end up looking like this. So, in some sense, right? If you're going to make lines and they intersect with each other, they will look like this. But that doesn't detract from the fact that somebody intentionally making lines is working with a visual pattern of some kind. And, and if they're making them and invest some kind of energy in them to engrave them on a rock surface, that probably indicates that it's striking some chord within them. And I think that's probably what we're seeing across these different populations.
Nick Jikomes 1:48:54
And I mean, this is just, I'm just giving you my pure speculation. My thought, my first thought when I saw this and was watching the documentary, I was like, do the number of lines match the number of bodies you found?
John Hawks 1:49:06
It's a great question. I don't know the answer to that. Because we don't necessarily know what the number of bodies is going to end up being. We have so far uncovered the remains of of more than 28. And probably it's something like 30 individuals in the different parts of the system. I do not think that this is anywhere near the minimum, I think, in fact, we're going to find that there are many more. And so I don't know what to I don't know what to expect.
Nick Jikomes 1:49:39
Fire. What is the evidence for fire look like?
John Hawks 1:49:42
We have quite Yeah, this is a great question. We have a lot of evidence now of charcoal and fire throughout the system. And the problem with fire is similar to the problem with engravings. It's very difficult to authenticate that this is coming from the same time as a hominin that was occupying the space Fire is one of those things that archaeologists are always very, I would say, rigorous about, they want to make sure that they know that the context of carbonized wood or charcoal in sites is coming from the same kind of context that you have other evidence of behavior, ancient tools or something like that. We have no evidence of tools of any kind, in association with miletti bones, other than one possible artifact in this burial and the plaster jacket. So we don't have cave surfaces that have lots and lots of tools in it. We don't think, on this basis, right? This is the evidence for it, we don't think that the lady was living in the parts of the cave where they found their bodies, we think that they were living in if they were living in any parts of the cave, they were much closer to the entrances. And we don't have archaeological material from those places at this time. So we've got a lot of charcoal, we have been working, we have some charcoal from excavations. And we will know the age of it. I do not know the age of it yet. And so what I can say is, for people that you know, want to know was Nicoletti using fire to get into these spaces. I've got a lot of evidence that there was fire. What I don't know for sure, I can't put it into the hands of miletti with any kind of chemical method yet that tells us how old it was. And it may be that we never will it may be that that's not going to happen. But I'm hopeful. Because we do have fire evidence in contexts where I know that we will have an age, I think that we're going to know a lot more about the chronology of the cave system and how Nicoletti may have been using it as we continue to work.
Nick Jikomes 1:51:53
How old are these bones? And what are the prospects of recovering DNA,
John Hawks 1:52:01
the bone material that we have the dates that we have on dental Edie material, which is which is a hominid teeth, right. So we know it's nobody is between 335,200 41,000 years old. That is 10 times the age of the oldest DNA in Africa that has ever been sequenced. So we may be some time before we have DNA evidence, it may be that DNA is not going to be preserved. There is DNA evidence from sites in Spain, that goes back to as early as 430,000 years. So it's not outside the realm of possibility. But we're in a chemical situation in terms of preservation. It's much warmer than the cold caves of Europe.
Nick Jikomes 1:52:46
It's possible but we cannot bank on it.
John Hawks 1:52:50
It's possible. I'm very hopeful. Our we have attempted we have done chemical testing to find out whether there's likely DNA preservation in the bone that we have tested, there is not. So that's where we stand. We do have a team that's working on protein analysis. And police on Madhu Bay and Enrico Cappuccini, who are at the University of Copenhagen are working on protein analysis from teeth and miletti. And we are going to have protein data from the teeth. So that gives us some biochemistry. With that kind of preservation. It's somewhat more hopeful that there may be DNA that we will recover someday. But it may take some technological changes before that happens.
Nick Jikomes 1:53:35
What do nullities teeth look like?
John Hawks 1:53:38
They they're strikingly human, like, if you don't know tooth anatomy, so they're about the size the molar teeth, the pre molars and their and their incisors are about the size of human teeth. They're very white and nice looking teeth. And the size differences are very minor. They're there. Their third molars are bigger than their others and bigger than yours. But otherwise, size is not very different between our teeth and theirs. Their morphology is different their pre molars, we would never have found a premolar like that and human today, I would think that this person is somehow a throwback from Australopithecus times their, their teeth morphology takes us back to very earlier, you know, hominids that lived more than one and a half million years ago.
Nick Jikomes 1:54:32
What so given everything sort of remarkable about this, but you know, you've got multiple skeletons where you've got lots of the skeleton. Yeah, so you know, as you know, and as listeners may or may not know, right? If you look at all of paleoanthropology, there's so many examples where, you know, our our evidence of something is one Jawbone or you know, whatever. I imagine you have males and females and I imagine you have quite an A age range here, what, what kind of demographic sample Do you have?
John Hawks 1:55:06
We have every age represented from infants, you know, including one very near birth, all the way up to the oldest adults that existed in miletti individuals whose teeth are worn down onto the roots. We don't know what age that is, we are working now to understand the pace of dental development. And that's going to tell us more about the age. We've got some preliminary results on that. And so we will know more soon about how long childhood lasted and how old children were. And with adults, when we talk about Neandertals, we tend to say, you know, I think the oldest Neandertals that we have, maybe in their 60s, but most of them, you know, more than half were dead before 30. And it may very well be the case more than half the reached adulthood, were dead before 30. So it may slightly the case with nobody, that it's something like that as well, that we have younger adults, and that's the majority of the population. About half of our bodies are children of varying ages. So we have a very strong representation of young individuals, male and female, it's very difficult for us to say, there's the skeletons that we have have very little size variation. If there are males and females both there, they were very similar in size.
Nick Jikomes 1:56:36
What like, what are give us a sense for like, what do you what are the immediate questions that you're working on that you know, or you're confident you can answer based on what you actually have to work with today?
John Hawks 1:56:49
You know, there's a series of things that are kind of logical that that will unfold, where I don't know the answer yet, but I know the method that we're going to use to get it and I know that we will follow that method when it makes sense, right. Some methods require us to destroy bone, or teeth, right. So we only undertake these with deliberation and with permits from the South African government, and with a lot of consultation. So I can tell you that we will know something about the development of nullity we'll know something about its weaning age, we will know something about, you know, exposures that they may have had during their life to things. And that knowledge is going to unfold slowly. The same is true of the protein evidence, right? I think we're going to know a lot about the proteins and miletti. But it's going to be a while. With the skeletal material. We know the anatomy of nobody better than we know almost any other species of human relative. We've published it in great detail, we've published hundreds and hundreds of pages of it, that the DNA, the data is available online, and other scientists are using it and applying it in their studies. Right Nicoletti is now the strongest example we have for for homo other than the Undertows in modern humans. And it's coming into studies in that way. With there's still unknowns, however, with the anatomy, right? We don't know what the ladies ancestors would have looked like. And we can do some work on its skeleton and Philo genetics to predict something about that, but will take us discovering individuals from other sites. And I expect and and anticipate that we're going to hear about another hominids that are similar to this from other sites, whether they're Nicoletti or not, you know, it's unclear, there's fossils that I've known about for a long time, that have been published as Homo erectus because of their morphology, where I look at it today. And I'm like, you know, actually, nobody is the most likely scenario here. I see. And, and those will be you know, will be reanalyzing things in that light.
Nick Jikomes 1:59:04
When the fossils that you just mentioned, where you have that thought to yourself, where are those fossils from?
John Hawks 1:59:12
The great fossil from Southern Kenya from a site called a log asylee. That's about 900,000 years old, that is just a part of the skull that's above the eye orbits, but its brain size, and its morphology look very much like miletti. So that's an example. There's some teeth from Southern Africa from sites where the tooth is by itself, or a part of a jaw, it's by itself, where I'm like, you know, actually, it looks a lot like miletti. But, but those kinds of things are just as difficult to assess as, as anti fossil is from a small fragment, right? It's like, what does it get me? If I discovered this tooth is actually miletti? Right against me a little bit more knowledge of its geographic and temporal extent. but it is telling me a lot more about its biology.
Nick Jikomes 2:00:02
Yep. Perhaps you've already hinted at it. But you know, in the next six to 12 months, any any major discoveries that you think will come out of either your guys's work directly or things related to miletti? Yeah.
John Hawks 2:00:17
You What can I anticipate? Obviously, we're working very hard on our descriptions of the burial materials, burial work and the art and, and that's in a process that eLife, where we're preprints are available, but we're still responding to reviews. And so that's coming. The, you know, some of the biochemical stuff may start to be coming out, you know, if we talk about six months to a year, that's possible. But what I'm most excited about is our continued work exploring other parts of the system, our work that we've been doing the last couple of years in the dragon's back chamber, which is adjacent to the dinaledi chamber, we are now analyzing material and hopefully, we'll be able to publish that and describe the context of that material next. And it's that kind of thing, right, expanding out our knowledge through this cave system. I will say that I'm also working on other sites with other fossils and other species. And I'm just as excited about some of those, we've got some really cool work that our team is working on that that I do think will be coming out in 2024.
Nick Jikomes 2:01:32
All right, John, thank you for your time. I want to make sure I don't take too much of it. This stuff is always fascinating. I always enjoy talking to you. And do you want to just give people you know where they can find you or follow along if they learn more.
John Hawks 2:01:46
So the easiest thing to do is check out my blog, John hawks.net, where you find sections on what I'm doing and some of our research that's ongoing and blog posts that go back now to 2005. But, but curated blog posts where I've really made a lot of effort to make sure that the information there is accurate, even when things have changed. Also, you can find our book cave of bones at any fine bookseller. I have seen it at a number of them and the documentary on Netflix still showing cave of bones. It is a really remarkable program. I have to say I was really pleased with it. I think it gives you a perspective on the kind of work that our team does in the cave system that you cannot get in any other way. It is it is really remarkable to see the team and we have an amazing team based in South Africa. South African cave specialists, my South African colleagues Lee burger can Eloy Mala piani to boho mocha Bella and and a number of others who are super central to all the work that we're doing. So I love seeing them on film. And I love seeing the cave. It's a really great way to see the work. All right,
Nick Jikomes 2:02:59
Professor John Hawkes, thank you for your time. Thank you