Full episode transcript below. Beware of typos!
Nick Jikomes
Thanks for joining me.
JOHN Hawks. Hey, thanks for having me. Yeah, no worries I. For those listening, I took a two courses with you about 10 years ago, in my final year of undergraduate, I snuck into them. I didn't have any of the prerequisites, but I was able to get in. And I just really wanted to take these classes before I got out. And I'm glad I did. Because it's an area I've always been interested in, even though I've never focused on it. And I mean, it's really, I think, a story, an area that everyone's interested in, because it's the story of humanity. That you probably you you probably don't remember when you actually met me. Oh, the very first interaction. That's right. I met you when you were freshmen. Oh, I don't remember that. What was that? We were doing a reading group with Jim Crow. Oh, yeah. We were reading ontogeny and phylogeny by Stephen Jay Gould. Yeah, that's an interesting book that world will ever want to read. very dense, but interesting book, if, if that's your cup of tea, and it has
John Hawks 2:54
a lot of history in it, I was really glad to be able to read through it and think about how that history applied. You know, now it's like, more than almost 15 years ago. But the, you know, when it was written in the 70s, and anticipated a lot of things, and and yet, the world, you know, just blew past it. And so it's always fun to look back at those things and think about well, the way that we look at things now, how would we have done it differently?
Nick Jikomes 3:22
So you're a paleoanthropologist. That's right, can you just briefly describe for people what is a paleoanthropologist?
John Hawks 3:30
Well, I'm an anthropologist, which means that I study humans and anthropologists study humans in a holistic way, right? We understand the connections between cultural, biological, linguistic, you know, elements of human behavior. And so the training of anthropologists is intended to be integrative in that way. paleoanthropologists studies ancient humans, humans that are now mostly extinct and how humans evolved.
Nick Jikomes 4:00
So paleoanthropologists often talk about the emergence of modern humans. So when did the earliest modern humans emerge? And what actually defines a modern human in terms of both anatomy and behavior?
John Hawks 4:13
Yeah, this story is really rapidly changed in the last 10 years. And so I'll give a very quick, you know, sort of definition right? What is a modern human, to begin with everybody that's living today, anywhere in the world is a modern human. So the basis of our definition is, it's the group that includes everybody living now. We have ancestors and some of the hominins that lived in the past, not so long ago, you know, 50,000 60,000 years ago, the Neanderthals for instance. They are very different from all living humans in in some important ways. And so the the frame of modern human puts us all together and separates us from some of these other populations that existed not so long ago, we emerged from Africa, our modern human population, and that emergence initiated sometime around 100 to 70,000 years ago. Before that time, all of the you know, I shouldn't say all I'll say, the vast preponderance of the ancestors of all living humans lived in Africa only. However, over the past 10 years, we've had some increasing complexity of what we understand about this. One of the things that, as I sort of alluded to, is that it's not all of our ancestors that came from Africa, we are related to these Neanderthals and, and some other populations. And they are among our ancestors, although a small fraction of our ancestry. Also, our diversification within Africa, which all happened well, before, 100,000 years ago, has, we've recently become aware of just how deep and complicated that may have been. We now think that when we look at people in Africa today, the initiation of the population diversity that we're seeing happen sometime around 300,000 years ago or earlier. And so our species, as it originates within Africa, is, you know, diversifying it's intermingling with other quite diverse hominins. And within the last 100,000 years, something happens that our species just sort of explodes across the globe. And so that, that history is something that we're very interested in.
Nick Jikomes 6:49
And that's something that happened, I, that's probably at least a partial, or mostly still a mystery. And did that have to do perhaps with the behavioral characteristics that define modern humans?
John Hawks 7:03
You know, there's, there's as many opinions about this, as there are scientists almost. And in the, the trouble is that when we look at the archaeological record of the early members of our of our group, the modern humans, they're making very similar artifacts in many respects to groups like the Neanderthals, that lived, you know, outside of Africa well before the emergence of our species. And so comparing those things, it's like, well, what is different here? It is possible, that there are differences that are not well marked by stone artifacts, you know, differences in social organization, differences in language differences in cognition in some way. It's also possible that it had something to do with with events that really weren't, you know, strongly related to cognition. One possibility is disease. And the reason we think of that nowadays is because we see that some of the genetics that we've inherited from groups like the Neanderthals are involved in immunity and disease defenses. And so we look at that and say, Well, maybe something was going on here, maybe there was actually, you know, interactions that were pathogen driven, that we're involved in the spread. Some people look at climate as a factor, and, and climate, both in terms of challenges with climate cyclicity within Africa, possibly creating the circumstances where groups are becoming more mobile, and, and logistically, depending on a wider space, which might have favored dispersal. And also the ice ages, which are constantly putting stresses on northern populations. And and so there's lots of ideas about this. And the answer is we really don't know.
Nick Jikomes 8:56
So we've already we've already brought up the Neanderthals. And you mentioned that this is a another population of humans. It's not a separate species, because we could interbreed. So how much interbreeding do we think was actually happening and who were the Neanderthals in comparison to modern humans?
John Hawks 9:14
We know the Neanderthals originated from common ancestors with our African ancestors. And I want to be, I have to be sort of precise in language, right? Everybody living today has a history of genetic intermixture that has kept our populations in contact and means that everybody living now has recent common ancestors and common ancestors lived within the last 10,000 years. Because of that gene flow. When we look at older time periods, we can distinguish we can see that there were fossil populations that lived in different parts of the world. They were genetically differentiated from each other. We have DNA from some of those populations. So we know how different they were. When I talk about our ancestors, I include all these people, because they're all our ancestors. But some of them, like the Neanderthals are really minority ancestors of living people. You and I, mostly Eurasian derived genetics, have maybe 2% Neanderthal in our overall genome. And so we can say our genealogies 2% of those at the time Neanderthals existed will trace back to them 98% of them will trace back to Africa. This is also true of other populations that exists at the same time, the denisovans are an example of this. So we have by far the preponderance of our ancestry from Africa, that ancestral group, differentiated from the Neanderthals initially sometime around 700,000 years ago. So the Neanderthals parted ways with ancient Africans, presumably, they were in Eurasia at that stage. And we have the first DNA evidence of them from a place called Sima de los quesos. In Spain, that's about 430,000 years old, that at the moment is the oldest hominin DNA that we have anywhere. So by that time, the Neanderthals are established as a population, they continue to exist in Europe, and in the western more than half of Eurasia. as far west, as you know, if you think of the area, where Mongolia and Kazakhstan and Russia and China all sort of nearly border each other. Neanderthals are that far. So, and that's their population. They are fascinating. We know a lot about their behavior, because Europeans have done a lot of work on archaeological sites. And, and the European record has some, some fairly dense accumulations of archaeological layers in caves, sites that give us an idea of their chronology for a lot of their time. But by no means all of it. And we're still working to understand Okay, how are they all connected to each other?
Nick Jikomes 12:20
So you, you mentioned? Well, when you think of paleoanthropology, at least when the average person hears that they probably think of bones. But you actually mentioned 400,000 year old DNA. So can you talk a little bit about the more recent developments in our ability to actually extract and study ancient DNA?
John Hawks 12:39
Yeah, absolutely. So ancient DNA has really transformed the way that we look at evolution, especially evolution of the Pleistocene. And there's some really, you know, important developments in this that affect our understanding of our own evolution. To begin with DNA is it's a pretty robust molecule, it stands up to a lot of abuse, but not everything. And in particular, it's preserved better in colder situations, it's preserved better and drier situations. So there are many parts of the world where we study ancient humans, fossil hominins, where the DNA is not available to us because it hasn't been preserved. But in the northern part of human habitation, in, you know, the sort of northern tier of Eurasia, and this is true from Spain all the way to to China, there is some remarkable DNA preservation, even not in permafrost situations where they build it yet longer. That we do have DNA from a 430,000 year old site in Spain, we have DNA from 250,000 year old sites from 120,000 year old sides. And by the time you get up toward the later part of Neanderthal existence, we have whole genomes at very high coverage of Neanderthals. At the time, you know, in 2014, when some of the first high coverage genomes were becoming available, we had better DNA evidence for Neanderthals than we had for all but maybe a dozen humans in the world. So we know we know a lot about them, at least from the from the nucleotide point of view. Wow. So
Nick Jikomes 14:28
by what time, are the Neanderthals gone? And what do we know about you mentioned briefly that we inherited some particular genes that probably had adaptive value that helped modern humans that came from the Neanderthals? What kinds of genes were we getting from them?
John Hawks 14:44
Well, I'll take the second part first, because it turns out here's a good example, right? In this week's news, the additional work on Neanderthal genes that modern humans carry shows that there's at least one gene that confers slightly higher COVID risk. And one gene that confers about 30% COVID protection that we got from the Android calls. And it's a great story in the sense that the message of human genetics of the last, certainly five years and probably 10 years, is that we used to talk about finding the genes for traits, right, you're gonna find the gene for bald headedness or find the gene for, you know, I don't know, having six fingers or something. There are, in some cases, genes that do those things, right, there is a gene for lactase. And that gene, by virtue of mutations that affect its its its expression, has a direct effect on whether you're a milk drinker or not, you know, as as a, you know, when you're not a kid when you're growing up. So there are cases where it is a gene, it's one gene makes a lot of difference. But for the most part, it's lots of genes. And in the case of most phenotypes that we measure hundreds of genes. And so when we look at, okay, we've got these genes from ancient people, what what do they do? It's almost always the case that it's a mixed bag. You know, if we look at one phenotype, they might do one thing on one gene might work in one way, and another gene might work in the other way. And you've got the both from this ancient population, right? broadly, there are some categories of genes that are overrepresented in what we got from Neanderthals, and other categories that are underrepresented. And so aside from particular things, you know, where we could say, hey, people who carry this gene have a 30%, higher risk of or lower risk of COVID. Aside from that, we can say that, over represented are genes involving immunity, and in particular, genes evolving involving innate immunity, and some of these seem to be antiviral or viral defense sorts of things. HLA we have HLA variants human leukocyte antigen, which is a major it's a it's a self recognition that your cells have and it's really important to immunity. And we have HLA variants from Neanderthals. We have some is enriched and what we got from Neanderthals is stuff involving skin and hair. Although it's not clear what it's doing to our skin and hair, it's not pigmentation stuff. We do have a couple of pigmentation things that are lighter pigment things from Neanderthals, but not a lot. Most of the lighter pigment things that are hanging around today in populations are young genes that have only been or young mutations that have only been around for a few 10s of 1000s of years. Yeah, so underrepresented. underrated, underrepresented are things involving sperm. And, and the X chromosome, we have a real deficit of Neanderthal genetic input into our population from the X chromosome. And looking at that a lot of scientists, you know, suspect that well, maybe there's something going on with, with the sort of hybrids that maybe there is a little bit of selection against hybridization with Neanderthals. And it's manifested in this sort of, you know, Gene deserts and the X chromosome and that kind of thing. So we're still working to understand, right, it but the problem from this point of view of an anthropologist, I have to say one of the cool things, is that the problem of understanding manatal genetics is not a problem getting Neanderthal genetics. We can look today at the advertised genes in the UK Biobank, where we have 1000s of British people that have the Neanderthal version of some jeans, wow. And you can look at to see what they do. Turns out that they make your head a little longer. That's one of the things that if people who carry lots of Neanderthal genes, they seem to have a little bit longer heads.
Nick Jikomes 19:14
But so speaking of that, so let's just paint a picture for people of how physically different Neanderthals were from humans. So what did they look like in comparison to us? And if there's Neanderthals walking around today, would they look clearly different from anyone we see on the planet or they be within the range of variation that we see today?
John Hawks 19:35
Well, in from a distance, if you looked at a bunch of Neanderthals, and they were dressed normally, right, people have done this thought experiment, right? If you're riding the subway with a Neanderthal would you notice and it's a it's a valid one to do, right? Because the differences that you would notice from a distance are, you know, they're basically human. body size, they're human and proportions, their arms and legs have the have the proportions that ours do. You know, they they're not they're not stereotypical, right, they're not walking hunched over. Compared to humans, the average Neanderthal, that we have skeletal evidence of, is a little bit shorter. So compared to today's people, but I have to say, right there well within the range of body heights among, you know, industrialized nations in the world today, right, I'm not even talking about some of the big differences between some small scale societies where you have, you know, some really small statured people. The turtles are within the range of variation of people that, you know, you might not see an exceptionally tall one, right? We haven't found any outer tall, that's taller than about five foot 11 or six feet. But the average is probably three or four inches shorter than the average, you know, sort of Northern European today. The they are a little bit sort of, I would say, they were built more like a wrestler. And I don't mean like professional wrestling, right, I'm not talking like WWE, but just that sort of a little bit life a little bit Bandy, you know, they look a little, you know, like, they're muscled, compared to probably the average person. But, again, with tremendous overlap, what is different about them, that we, you know, sort of, you have to look at the details. And the details in the skull are probably the most obvious, in the sense that Neanderthals have a brow ridge that is continuous that goes right above their orbits, that projects forwards, they have faces that are projecting forwards, more than probably anybody that you know, right. So they have that kind of form. And the back of their head is a little bit elongated. And so their skull has a little bit different shape from ours. It's similar in size, their brains are human sized. But but there are these differences, that that reflect something about their evolutionary heritage. They don't have chins, in the sense that that we have modern people have projecting chins that they really stick forward a good bit. There's variation in that. But I'll tell you that people who you would describe as having a weak chin, if you looked at the bone inside of it, you'll still notice that there's some projection to it. And the Enter tools don't have that they have tall faces and tall, tall mandibles. But but they don't have projecting, right. It's not, you know, there's no Kirk Douglas Neanderthal. But, you know, that's sort of a, you know, a broad description. Yeah, the things that we notice about them. You know, today, as anthropologists, a lot of those have to deal with the fact that they live in small scale societies without the sorts of technology we have. And so big fingers and no sort of splayed feet, and the sorts of things that people have these things that today's people have if they live without shoes, and work hard. And so, you know, a lot of the differences that you would notice are actually human traits that that we just don't see. And in lots of comparative samples we work with.
Nick Jikomes 23:33
I see. So one of the things so they had big brains just like us. Yeah. And when people think about the I'm gonna hesitate to even say this, the uniqueness of humans. The thing that you often talk about first is how smart we are. We've got really big brains, and we can do stuff, we can invent things. And most people recognize that our brains got really big over some period of time. And I always hear different numbers thrown out. But can you maybe talk about? So early modern humans arose last 100,000 years or so? How far back? Well, how many years go from today back to our common ancestor with chimpanzees? And how big brains get in between then and now? And was it a linear change incrementally over time? Or was there more a different kind of pattern of evolution there?
John Hawks 24:21
Yeah, sure. So our evolutionary ancestor, our common ancestor with chimpanzees and bonobos lived something like seven to 9 million years ago. The earliest hominins that we have fossils of are between six and 7 million years old. So by that time, our lineage is established, we're headed off on the path that we are. We are our ancestors are clearly bipedal walking on two legs and have skeletal adaptations that make us rotten at walking any other way, by four and a half million years ago. So maybe the first third of our evolutionary history were sort of Becoming bipeds. After that we got a lot more fossils. And in between about four and a half million and 2 million years ago, the world is Africa is full of creatures that we today call Australopithecus or Australopithecus. And this is not as simple a story as saying that they're all Australopithecus. But I'll say that there are many species of them, they all are upright walking like we are, they all have brains that are between about 400. And at the high end, about 550 milliliters, our brain size today, average for men around the world is about 14 150 milliliters average for women about 1350. So when we look at these early hominins, we're looking at creatures that have about a third our brain size. But a slight slightly bigger than chimpanzees. I will say chimps are between 350 and 450. ish.
Nick Jikomes 26:02
Wow. So at this time, there's apes walking around. on two legs, there's many kinds of them. And their heads are a little bit bigger than chimpanzees.
John Hawks 26:12
That's right. And, and they're diverse, they have different dietary strategies. Some of them have really big jaws and teeth. And, and some of them have big jaws and teeth compared to us, but small compared to the others, you know, and so they're none of them are very much like chimps, it turns out, you know, they're doing they're, they're pulling a different trick than chimpanzees are. And part of that is living in more open country, and probably diversifying their resources. But we don't understand fully what's going on with some of these, the diversity of them is important, because we don't know clearly which one of them gave rise to later humans. 2 million years ago, our jenis is on the scene homo, and it's marked by a little bit larger brain size. With homo, we're talking about something like 500 to 650 milliliters, maybe 700 milliliters in the early members of our jenis. And, and that is a jump. The first members of Homo that we're aware of have bigger brains than Australopithecus. The after that, I will mention that most anthropologists and anatomy included in this think that using stone tools had something to do with this. Because Around this time, we have stone tools. But stone tools have a little bit longer history today. We know that some Australopithecus, you know, species must have been using them. And it's not and and chimpanzees and bonobos are tool users, you know, so we know that tool use is something that goes way back. And so the question of how tools relate to behavioral change and and ecological change. It's not super clear. After 2 million years ago, argenis diversifies? And the answer to your question, Is this linear or is it some other pattern? The answer is it's a tree. And what we get is some lineages within our jenis that we call homo, that start to get bigger brains. Homo erectus is one of those. By a million years ago, we have species that today we call homo antecessor that Neanderthals arise by 700,000 years ago, these are all getting bigger brains. At the same time, we have other species that continue to evolve and persist, that retain smaller brain size in our Janice. One of those is a species that I work on in South Africa, we discovered in 2013. It's called Homo naledi. And it had brains that were basically like the earliest members of Homo in size. Another one Homo floresiensis discovered on the island of Flores in 2004. And, and retains a brain size of about 450, maybe 400 to 450 cubic centimeters. So you've got these small brain versions of our jenis and some big brained members. And the progression toward the evolution of today's brain size is something that we can trace through our common ancestors with Neanderthals, and probably Erectus, but the pattern of it is not 100% clear.
Nick Jikomes 29:41
So one thing you mentioned briefly was diet. So, you know, there's there's a couple of things I'm interested in learning about. So one is the stone tools and the complexification and sophistication of tools over time. And the other one is diet, I imagine and I know that there's some pretty Prominent hypotheses out there around the relationship between our evolving diet and our brains. So brains are expensive, takes a lot of energy to run a big brain. And there's this kind of chicken and egg problem, I think, where did we start eating more nutritious or more calorically dense foods and that power to our brain? Or did our brains power our ability to figure out hunting problems in new ways and figure out how to cook food? So what is what is known about the relationship between cooking hunting and food sourcing and and getting bigger brains?
John Hawks 30:35
Yeah, so this is a really hot research topic. And our knowledge in this area has changed a good bit. And I want to point to some cool work. Herman Ponsor is a research scientist and anthropologist who's really focused on energetics and activity, especially in hunting and gathering populations. today. Richard Wrangham is a scientist who has primatologist, he's been a lot of thought into what difference cooking and fire might have made to energetics. I want to sort of name check those guys, because what we thought 20 years ago, was that the origin of Homo correlates with the first stone tools, and the so inventing tools, we're doing that to be able to better exploit hunted foods, and we're becoming hunters. And really good scavengers have meat. And so we start getting meat in our diet. And meat is energetically rich. And it's a resource that gives us the you know, sort of better protein and the access to higher, you know, lower effort, lower chewing higher energy food. And so you have this sort of idea that, here's what happens. We become human because we become meat eaters. And that hunting pattern selects for larger body size, larger brain size comes with larger body size. But using tools and having to cooperate with each other to hunt also requires us to be smarter. And we pay for this by having better food. So there's the kind of cycle and the idea was, well, this all happens 2 million years ago, between two and a half and 2 million. Today, we think slightly differently about this. And and I can't say that we know the end of the story yet. But I'll tell you why the story is somewhat different. First, the earliest stone tools we have are now three and a half million years old. So Oh, wait stone tools are there a million years before agenda? So something is going on here. Second, this research, especially Richard Wrangham thinking and and also a point to Kristen Hawkes, and other folks who look at hunter gatherer diets are saying, you know, wait a minute, these underground tubers and and other kinds of plant parts are systematically collected by today's hunting gathering peoples in Africa, they make a lot of difference to energy, and they're available to you once you can cook. It's it's cooking, that allows the reduction of some of the less easily digestible fibers and starches and makes more nutrition available to you. And, and so and so this idea of, well, maybe this is a plant consumption transition. And maybe the first important tools are digging sticks, you know, are is is a real player. The other is we used to have this idea that we're energetically constrained that primates basically have an energy budget that's depend that is determined by their body size. And so if you are going to get a bigger brain, you got to save energy somewhere else. Turns out that when you measure the energetic output of hunting and gathering people's and, and other primates, actually, we spend more energy than other primates do. One aspect of us becoming human was actually burning more energy. And so we're collecting more energy. Well, this is all sort of complexified the picture, it's not quite clear yet how this all goes together. It is very likely that diet change was really important to the evolution of argenis and the appearance of many of the species within our jenis because we see the evolution of the teeth. However, this is not at all obvious what the teeth are used for. I mean, we use them for chewing. But the the micro wear on the teeth is not giving us a clear signature of differences in what they're eating. The isotopic composition of teeth and bones is not giving us a clear difference idea of what's what's going on. And so and so the evolution of diet is a really big problem.
Nick Jikomes 35:00
Interesting. Yeah, so it clearly plays an important role. We just really haven't teased it out yet. But it sounds like at some point, there was clearly more of an emphasis in our diet on meat.
John Hawks 35:11
Yes, it's we today, hunting and gathering peoples around the world, right. And we use these as today's analogs of what people would have lived on before agricultural and pastoral diets came in. It's not to say that anybody in the distant past lived the same way that today's hunting gathering societies do, it's just that they're the analogues we have, they're tremendously diverse. The che in Paraguay eats something like 70% of their calories from meat, the hodza, in in central Equatorial Africa, East Africa, have, you know, sort of the opposite ratio, you know, it's like 25, or 30% of their calories from meat. But this is a big shift compared to chimpanzees who are hunters who are meat eaters, who get something like 5% of their calories from meat. So, meat is an important resource for humans around the world. It's more important for some than others. But it's something that requires a different pattern of social organization to acquire. Yeah, and that's why we're really interested in as anthropologists, because a lot of the interesting social interactions that chimpanzees have, are focused around these kinds of group hunts. And and so we look at that and think, wow, you know, something interesting is probably happening with social organization, and hunting.
Nick Jikomes 36:40
Yeah, yeah, that makes a lot of sense. So there's the there's all these complex feedback loops between the technology, we're developing the social organization, we're developing the ability of those things to further aid in a bigger brain and body, which then feeds back on to those other things. You mentioned that by the time homo, by the time humans were around, there were stone tools. What were those earliest stone tools? What types of things were people doing with
John Hawks 37:05
them? Yeah, so a stone tool is, first of all, stone tools or rocks. And the first thing that anybody did was just use a rock and pound on things. And we actually have rocks where we see the evidence of the pounding. So So that is an element of the earliest assemblages
Nick Jikomes 37:25
of chimpanzees. Do that with
John Hawks 37:27
chimpanzees do that also. And we have chimpanzee tool assemblages, that are archaeological that you go out to West Africa, and dig in places that chimpanzees have lived. And you find ancient chimpanzee tools, the rocks that they use to crack nuts with. And those rocks have characteristic flaking patterns, when you hit them hard enough on something, they actually have little balls of flake that come off of them. And you find that so the archaeological record, in that sense, is much broader than humans. We have an archaeological record of capuchin monkeys, an archaeological record of mechanics, because they're using stone, and they make characteristic changes on the stones that they make hominins. By 3.3 million years ago, were deliberately fracturing stone to make flakes that they used as cutting edges. And so that element of it of having in your mind, I'm going to take this rock and deliberately fracture it so that I have a piece I can use for something. Yeah, that's, that's a transition that we can teach chimps to do. Kanzi, the the famous bonobo, who is who is well known for communication experiments, was taught by Nick toasts, the archaeologists to make stone flakes. And so this is well within the cognitive resources of chimps. But whenever a possession spontaneous, they don't transmit this in the in their natural habitats. And they do transmit other tool making another tool using so some pretty cool examples of honey probing sticks, that that chimpanzees have these underground bees that they that they go for honey. And they use one kind of stick to probe into it. And a second kind of stick to sort of widen the hole and a third kind to actually fish out the honey. So they they transmit this right, so the cultural transition transmission is something that they do. But and, and so, when I talk about early stone tools, what I want sort of people to understand is that probably we're looking at apelike cognition. Yeah. But with a particular tradition, that that they are maintaining that tradition is one that's focused around cutting edges
Nick Jikomes 39:59
and what do we want? were they using the the tools to cut?
John Hawks 40:03
They were using them to we know that early in this, they were using them to cut meat from bones in some instances. However, there's a big caveat here. And and the caveat is actual genuine arguments between archaeologists about what they're seeing, when we see cut marks on bones. There are lots of things that make marks on bones. So we have to really think through, you know, have we demonstrated that this is deliberate that it's corresponding to butchery. And with some of the earliest evidence, it's hard to do, in large part because crocodile teeth makes cut marks that look a lot like stone cut marks. And we just haven't gotten past that yet. So the earliest cut Mark evidence is debated. But by two and a half million years ago, it's clear that there's there's abundant evidence of we're cutting meat off of things. So that's part of it. We do have some use where evidence from tools that are before 1.8 million years ago, so I've come up almost halfway to the present. I'm not ignoring that we've left half the archaeological record behind. But at this phase, when we have some big assemblages, and folks have studied with electron microscopes, they can see characteristic wear on the tools from cutting meat from Luke, which makes a polish on them that is fairly distinctive from cutting wood. And, and from being worked on other stone. And so they are using tools at that phase for a diversity of stuff. But by that time humans are homo is around. And so and so it's not clear that, that we're looking at the same kind of thing as the very earliest examples.
Nick Jikomes 41:54
So the details are still to be filled in. But the the contours of this early story are that there's clear interactive effects between people or apes, the proceeded people getting smarter. They're starting to use tools, in many cases, if not, if not the primary case. They're using them for things related to meat. And there was probably more sophistication around how we hunted to get the meat. And therefore how we were organized socially. Do we know? Is there an approximate time period where we know that early homo was organized in social groups in a way that was clearly different from chimps or bonobos?
John Hawks 42:33
That's a tough one. In part, because the key evidence is the most important evidence about organization comes from evidence of food sharing. And because that is something that humans rely on, right, we have to share food. And chimpanzees and bonobos do share food, but do so sort of in some in a lot of cases under duress. So, food sharing is something that we you know, it's our life breath. And for them, it's like, well, you know, we'll play this into our social interactions sometimes. And so most archaeologists who thought about this are thinking in terms of large packages of food, like, hunted, you know, Bob, it's, Bob is are antelopes. And so, in the older one times, something like 1.8 2 million years ago, there is some good evidence of hunting in the form of death distributions of antelopes, where you can see that Wait a minute, humans are selecting the ones that they want. He usually we're selecting the meaty ones. And yet, there's, there's species where we're clearly selecting what we want. And other species were the ones with cut marks on them are the same distribution that a lion might hunt, you know, the old and weak and the and the babies. Turns out that this is size related. And in the earliest archaeological situations, we hominins seem to have been really good at hunting small antelopes and not very good at hunting the big ones. Now a small antelope is still probably a food sharing situation. And and I sort of think that probably if you want to say when did the hunter gatherer type social structure emerge? I think probably then, I think probably it really is tied to early hunting and the logistical strategies you have to have to share food and and balance risk of failing to find food across a group of six or eight into six or eight adults.
Nick Jikomes 44:50
Yeah. And, you know, with their kids, there's this logistical and strategic issue which which requires a certain level of cognitive Sophists. The occasion, you also mentioned this correlation with the size of the antelope. And sometimes it looked like we were eating things that Elian would eat. And I know that there are ideas out there around humans being power scavengers really good at hunting, but also stealing the kills of lions and bigger, tougher creatures, which presumably required group coordination weapons. And, and this is where where I start to get interested, especially the ability to communicate verbally. Yeah, yeah. When does when does language or proto language start to come onto the scene? As far as we know? I mean, do we know? Do we have like a good time range for that? And how does that tie in to some of the things that we've been spooling together already?
John Hawks 45:43
What we have in terms of evidence of language, that it's not archaeological, right? It's when we look at tools and say, What would it take to be able to communicate that? Set that aside, and say, What do we have for evidence of language? The dissatisfactory answers, the unsatisfactory part of this answer is that we have bookends we have we have a before and an after. And the problem is that the book ends are very far apart. And so when I look at what is evidence of honest to god language, I would say we want evidence that relates to the vocal auditory channel, you know, we use our vocal cords and and mouse to talk, we use our ears to listen. And those two things are pretty tied to to our language use. We know a good bit about this now. We didn't 1520 years ago we do today. The reason is largely fossil discoveries. We have a child of Australopithecus afarensis, solusi species that comes from a place called de kikah, Ethiopia, and that child, it's probably about four years old at the time that it died. But it's preserved with its entire skull and jaw, bone and neck and everything, including the hyoid bone. We have so few hyoid bones in the fossil record, it's thin, it's not preserved real well. Those of you who watch CSI, this is the thing that the investigators are always trying to figure out if it's broken, because that's a sign that you were choked, right. So it's in, it's actually right next to your your vocal cords, your your voice box, your larynx. And the shape of it is different in humans compared to other great apes, chimpanzees, gorillas, orangutans, they have a vocal sac that actually attaches to this and and creates a shape. That is that's broader than than our hyoid bone is. So the kikah has an ape like highway. Australopithecus has, basically ape like ape like middle ear bones. Humans have middle ear bones that look a little bit different from chimpanzee middle ear bones, we have a highway that looks a little bit different. We have evidence of both of these in the fossil record. But the evidence that we have of both of them comes from the first Neanderthal site, that same 430,000 year old site. So by that time, I can tell you that the vocal tract and the auditory tract had both evolved in ways that that humans use for language. So Neanderthals, and our common ancestors with them I infer had vocal auditory communication in a similar way that we do.
Nick Jikomes 48:45
And presumably, I guess what's tough there is, when you see those anatomical features, it tells you that for sure, we were physically enabled to develop language, but there was presumably some period of time after we had the physical features necessary to do it. And and the cognitive capacity to do it. And then we actually did it.
John Hawks 49:04
And that's the thing, right? Yes. Is, is a, it's like we're looking at each other, right? And we're both using these headphones and microphones. And we know from the presence of the headphone and the microphone, that something interesting is happening. But what we don't know is is what what the content of that of that channel is, right? How much information is that channel communicating? And how widespread was the communication? You know, when we look at language today and all of the aspects of it, it's not only important in terms of telling somebody something that happened, right language is the when your toddler first starts to use basic language. It's a transformation in your life. You know, just having a little bit, you know, I need to pee. That's not a lot of content. But it's highly relevant content. And if you can communicate that and and send that signal, it's important to you. Well, the fact that by the common ancestors with Neanderthals we have hearing and speaking, you know, in the sense that the the anatomy is there tells us that there was selection for it. But it but we don't know at the moment is when that selection initiated. And, and, and what its pattern was, you know, is mainly selected because you're sending these these messages to people, in which case you want to tell a story to selected for social, purely social reasons. You want to talk about social status, or you want to, you know, coordinate activity? The answer is we don't know.
Nick Jikomes 50:50
Interesting. So by, you know, I think he said it was for 400 150,000 years ago was our common ancestor with Neanderthals about 700 or 700. Okay, yeah. So 700,000 years ago, we could have had language, it could be at least that old. It might be younger, we don't know. What about.
John Hawks 51:11
So we might be much older, I just want to say, right, if you could go all the way back? You know, it's, we know, it's not as oldest as Lucy. But were in that that, you know, this began and what would have been useful to our ancestors is, is, at the moment, not enough.
Nick Jikomes 51:31
So what about, let's talk about the social complexity in the social organization of early humans a little bit more? Can you take us through a little bit of, you know, what's the average group size and group dynamic of say, extent, hunter gatherers? And, like, approximately, when did we get to that, and I guess how much diversity is there even among present day hunter gatherers?
John Hawks 51:56
That That part's easy, there's a ton of diversity. hunter gatherers historically have have included desert groups that live at very low densities, in some cases, as low as one or two people per 100, square kilometers, you know, so they range over enormous distances. And, and, and live in relatively small bands in traditional term, and anthropology is the band for that size of group. And that band involves, you know, something like eight or 10 adults and the children and that are with them, you know, so groups of something like 25 individuals, that's a classic way of looking at this, that's the 1950s version of anthropology was this was the ancestral social organization. But many hunting and gathering peoples are pretty sedentary, you know, they sort of stay in one place most of the time. And some of those societies, especially in the last 20,000 years have been enormous, have lived in communities of hundreds of individuals. We don't know how early these larger communities became important. And that's a real frustration for us, I have to say, right, because, you know, we find bodies, and usually little parts of bodies, we find some sites that have a density of activity to them. But the places where we have, you know, really great archaeological evidence are not today's population centers, you know, in the prime places in well watered river valleys. with, you know, we don't have a dense Paleolithic record from the Nile River Valley, you know, are some of these places where you might have thought, Well, people, you know, they would have lived there in the past, because we like it there. Now. You know, part of that is that we're living on top of them now. But that's not all of it, right? Because the fact is that where we live today, we tend to dig and to make houses and nothing else. And so you tend to turn up history. And the history in these places is actually, you know, is pretty obscure to us. So, today's people tremendously varied in the size of groups and the mobility of groups. We know that that variation extends some distance in the past, we don't know how far
Nick Jikomes 54:26
and so by comparison, what would be what would be a typical chimpanzee group size today.
John Hawks 54:32
chimpanzees live in communities that average around 50 individuals, they tend to forage in much smaller groups and lots of times the mother and her offspring, or you know, a few males in a little little group, so they'll split up as a community and then come back together. And those those times when they are, you know, in a large group are times of food abundance, you know, there's enough there's a tree that's got lots of fruit on it, and so they're all in one place. What they are organized about as a community is occupying space and, and keeping other groups out of the space. Whereas their day to day activities are, you know, tight with a much smaller number of individuals. And that kind of fission fusion society does occur among a lot of primates. You know, it's not just chimps, you know, it's, it's a lot of primates, that seems to be a stable way of interacting. I see.
Nick Jikomes 55:27
So by the time homo is on the scene, there are some stone tools are walking on two legs, our diet has changed to some extent, we're probably getting more calories, that somehow are fueling further changes in the future. At some point, we learn how to speak. We don't know when that is, but it could actually be fairly old. Yeah. When we learn how to speak or by the time we learn how to speak or capable of mental imagery of some kind, symbolic thinking, group dynamics are changing. I have more questions about stone tools. So we go from the bludgeon to the flake cutting stone tool. When do other stone tools that are more sophisticated come online? When do we get to things like projectile projectile Spears, and bows and arrows and those kinds of things?
John Hawks 56:16
Yeah, the first thing that most people think of is the hand axe. And hand axe is sort of a teardrop shaped stone that is flaked around each side, and on both faces of it, and all around the edge. So as soon as there's sharp all the way around, and hand-axes come on to the scene around 1.8 million years ago, in Africa, they persist. I mean, recent historic and and Holocene peoples made hand-axes fundamentally, they tended to be polished hand axes in more recent times. But the hand acts as a tool remains important in different places in the world up until historic times. However, it is more common in some times in places and others in the heyday of the handaxe, the time that we call the Ashmolean period, extends from about 1.8 million years ago, up until around 180 200,000 years, in some parts of the world. In some parts of the world, it's never happening. And so and so there is a heterogeneity. Probably from those earliest phases hominins were sharpening sticks and using them as Spears, right, I can say this with some confidence for two reasons. One, chimpanzees, sharpened sticks and use that Miss spirits. So the idea of it is not beyond any hominid. But the other is that, you know, the earliest wooden artifacts that we have in the archaeological record, which are not super old, they go back about 400,000 years are sharpened Spears, and they are fire hardened Spears, they do not have any kind of stone point attached to them. So this must have been a very important type of tool. Digging sticks, also, were almost certainly important tools. But we just don't have them in the fossils in the archaeological record until the last half million years. The first the next sorts of things that happen, right, if you want to say what are the big events in the in the archaeological record, the next things that happened are about a half million years ago. And people start to to use stone flaking techniques that that add a little something compared to making a handaxe handaxe is an elaborately shaped artifact and some of them are really, you know, just finely crafted.
But
a little bit later, people begin to focus on making tools whose final shape is pre determined by the shape of the of the stone that they're flaking. So handbags, sort of start with the rock and keep removing stuff until it's handaxe shaped. The levallois method of stone tool manufacturer, you take a rock and you shape it and shape and shape it until it gets to the point where you know that if you hit it in just the right way a perfectly formed point will come off of it. And and that trick is something that occurs here and there in the Ashmolean, you know, up to a million years ago, you see semma levallois flaking, but it becomes a dominant mode of toolmaking around 300,000 years ago. At that stage, you start to see people making these points and sticking them on to spears. And so you've got something a little different. That's happening at that stage, you're using glue, you're fixing things together, you're making compound tools, you know. And and that's, that's a trick that seems in time to be associated with the beginning of our species. What's not clear is whether it's only our species is doing it. The advertisers did it too, right? So, so if we consider Neanderthals, they're all humans do, right? It's not clear whether it's just us just the big brain, guys, whether this is broader. I see.
Nick Jikomes 1:00:32
So as our groups got bigger, as we started to have more sophisticated cognition, we started to be able to make better tools, we started to be able to coordinate better with each other for hunting and for other purposes. At what point? Do we have clear indications that people really cared about death in the way that humans do compared to other animals? What is the earliest evidence for, say, say, a barrier, an intentional burial.
John Hawks 1:01:01
So this is right now, this is a subject that I'm really engaged with. The reason is our site in South Africa, the rising star cave, we're working 250,000 years old, a cave chamber that has is full of hominids, and those hominins, we have, at the moment, at least 25 individuals of this species in a couple different parts of the cave, they're using these deep parts of caves of this cave system. They're, they're using them repeatedly, across a broad area of the cave. And what we have in these deep cave chambers is their bodies, and not anything else. And so, you know, after ruling out other kinds of natural, you know, sort of modes that they might have ended up there, we're left with Well, they got themselves there, right. They, they were depositing their bodies in this place. That the moment this is the earliest evidence we have, from archaeology, paleontology, of a any hominin acting like they care when somebody dies. Now, I don't think by any shot, that this is the earliest that that existed, I think, honestly, right, our common ancestors with these miletti have an answer, probably, certainly more than a million years old, and probably more than 2 million years old. And so you know, this is something that may go quite a long ways back. We know that modern people, and Neanderthals are both deliberately creating holes, putting bodies in them and covering up the bodies, in many cases, along with stuff. So that sort of classic, okay, they're burying bodies, they have some kind of ritual that's happened here. And they've, you know, buried it with stuff is something that the capability for it has emerged before, 200,000 years ago. And the basics of recognizing death, and maybe doing something cultural, at the time of death is something that may be quite, quite broad in the hominids. We are interested in that because we look to other primates and other animals, other mammals and say, what's going on with this right? What is what is actually the change that's happened here? Because we do do something that no other mammals do. But the exact description of what we do is not easy to come up with because other mammals grieve social mammals care, they, they their behavior is altered when individuals within their group die.
Nick Jikomes 1:03:53
Is that clearly demonstrated? Would that be like elephants?
John Hawks 1:03:57
Oh, yeah, yeah. That the elephants, oh, many, many kinds of primates, social carnivores. There's lots of examples of cetaceans, lots of examples of somebody dies, and others who have long associations change their behavior. And in ways that appeared characteristic of grieving, right, there's a loss mothers who lose infants often will continue to carry them for a long time, and and that among other primates, and that behavior has been studied in quite a lot of cases. And that seems to be something beyond you know, the the altered behavior that seems to be something that's that's very, very deep. What do humans do? That's different from that is a tough question to answer. we grieve right and we talk to each other about our grieving. We that's something other animals don't do. Yeah, they have social experiences of it, there are lots of cases where they approach a dead body or a place with skeletal remains that might remain from a dead body and have an exhibit shifted behavior. Humans do more than that, we have a communal memory of it, we talk to each other about it. We engage in ritual associated with death. And that ritual is the existence of ritual, the cultural performance of ritual associated with death is universal. Every culture has some kind of ritual, although they differ enormously from each other.
Nick Jikomes 1:05:45
Yeah, so I want to dig into that a little bit more. So this, this ritual lipstick behavior surrounding death is present in all fully modern cultures we're aware of you said that burial goes back at least to the common ancestor with Neanderthals. So that's 700,000 years at least?
John Hawks 1:06:01
Well, well, well, I want to be as precise as I can, right? If I said, What goes back, right? We have burials of Neanderthals and modern humans, we have pigments of Neanderthals and modern humans are using pigments, and apparently, you know, making art too. But most of the evidence for that is late in the span of the Neanderthals. And so there's a question of, you know, is there some interaction that has happened that causes this, you know, or is there ursday? Is it a shared ability that goes back to the common ancestor and is latent and is manifested later? Or does the behavior go all the way back? And we just haven't found earlier evidence of it? And any of those are possible?
Nick Jikomes 1:06:50
Yeah, I would imagine this is the type of thing a lot of these things are probably, of the form that, you know, the earliest clear evidence of something, it's probably a little bit older than that, at least, right? Because if you find a clear evidence of a burial, there was presumably a period of time where there was just a less robust burial process, we're just burying people in twigs or something, and you're simply not going to find that.
John Hawks 1:07:14
Yeah. And, and with something like this, where burial is one extreme of what we see among living people, right, if the extreme is most likely to preserve. Whereas most of the rituals that we have associated with mortuary or you know, around the world, are less likely to preserve, you know, the ones where you're, you're curating the heads and keeping the head in the basement. Well, that's a pretty good one, if you have basements, you know, but if you're keeping the head, you know, I don't know, you're carrying with you some distance or something like that. It's less likely to show up. And if you expose them, so that the vultures come? Because carrying your spirit into the air is the highest manifestation, then we find nothing. Yeah. And, and so it is a struggle thinking, Okay, we have this very strange combination of circumstances that enable us to study this. But those are limited in what we see in the world today.
Nick Jikomes 1:08:17
Well, you did mention that in some of the earlier burials, we have evidence of you find the body, and then you also find artifacts. Is there any pattern of what kind of artifacts tended to be in those earliest burials we know about?
John Hawks 1:08:32
It's kind of diverse and diverse to the sense that there's argument about about border cases. Right? So the clear cases, you find the jewelry? Yeah, here's the leopard claw was worn as a necklace. And then you have cases where what you find the artifacts? Okay, well, this is a beautiful point, maybe that one was, you know, sort of intentional. But here's the sort of ugly point. And it's not right on top of the body, you know, sort of near the body. There's a very famous case law faricy. In France, where the bodies were, one of the bodies was found, two bodies were found head to head, and one of them had a limestone slab. And the limestone slab had these sort of little kooples, these little depressions that seem to have been intentionally made in it.
Well,
the slab isn't like, exactly on top of. And so there's this question of, was this intentional? Or is it just sort of happenstance? And does this have nothing to do with the bears? Maybe maybe the people left the slab didn't even know the bodies were there. And that kind of thing. makes it tough. There are lots of cases where, arguably, there's stuff in the grave, but archaeologists disagree about what That stuff was really in the grave. But yeah, it's it's in the dirt that is near the thing near the body. But was that put there? Or was it just scooped in? When they were covering the body up? Yeah, it makes it really tough.
Nick Jikomes 1:10:17
Okay, so at some point, though, we have human cultures around where there is this very acute awareness of death, there's very well defined rituals around death, even while before people die, they're talking about it, they're expecting it, they know what the rituals are. There's often a, you know, I know that there's some later sites where you find shamans and other presumably high status people buried with specific types of artifacts, one of the things I'm interested in is shamanism, or what you might call, you know, early proto medicine, and things like the use of botanical knowledge to, to use medicines in society, or to perform rituals or whatever. So there's, there's early graves, I shouldn't say early, but there's some graves that are found where you find cannabis samples, for example, or you find other botanical samples. When does that stuff start to come around? And and how, I guess as an anthropologist, how would you define shamanism? And is that something that's more or less universal among hunter gatherer societies?
John Hawks 1:11:22
Yeah, you've asked a big question. shamanism is a kind of, I guess, you'd call it a belief system. Some would call it religion, and others would limit religion to things with that have sort of organized, organized social practices that are associated with them. And shamanism sometimes is that but isn't necessarily always. Every society around the world has beliefs about supernatural things, and the place of humans and many societies. I can't say all because my knowledge isn't that wide. But I'll say many, many societies have some kind of social role for somebody to be the arbiter of that they tell you the stories. And shamanism is sort of a contiguous. It's contiguous with that social role. It's like if you take this a step farther toward, you know, being the the person who has the secret knowledge, and who's the transmitter of the secret knowledge and is, you know, in communion with the spirits, that's what's considered to be part of shamanism. We don't know, in the, in the archaeological record, right, we could go back to, you know, sort of 5000 10,000 years ago, where you have early villages and, and some high density hunting and gathering societies, where you have clear evidence of social differentiation, right status roles that are marked by different health in different individuals, different set, in some cases, you can find lifespan associated with, with these sort of health markers. And, in some cases, special artifacts, or special places, right? There's some where it's very clear, this is the man's house, you know, where you have these associations of man and those secret societies etc. that stuff was sedentary high densities, populations, archaeologists, can trace and have found. And Kent Flannery's work from the University of Michigan is somebody who's really looked into the origin of social social differentiation and and inequality, you would say, in the archaeological record, but it's just a way of saying that there are different roles. And those roles are marked by artifacts. Before that, we have almost no evidence of social differentiation, right? We need, we don't find clear evidence of individuals that have social markers that set them apart from other individuals in the same society until we have sedentary societies.
Nick Jikomes 1:14:17
Is that because it's easier to see those things in such societies? Or is it because you've had the opportunity to find that stuff, but it's just not there?
John Hawks 1:14:26
It's not clear. I gotta tell you right from from looking from my point of view, unlike what I look for, in the archaeological record, setting aside the sorts of stuff that you know, ethnographically in different societies around the world, you see that there's, there's a place in the village where they do the things, there's a place where they keep the secret stuff. You have to have a place to keep the secret stuff in order to have secret stuff. Because if you're carrying it around, it's not secret. We don't bet more than The point right before, no before, really before, 25 30,000 years ago, right, we have intensive pigment marking of burials. At that time, we have, you know, widespread use of pigments, we have the creation of artistic, you know, objects, these sorts of ivory sculptures, that sort of thing. We have the markings on cave walls. Many archaeologists, anthropologists would say, look, the cave art is kind of a sign that you have some kind of belief system, some kind of transmission of knowledge, you know, that's probably enough. And those are happening, you know, around the world, Southern Africa, in in Borneo, some of the most in Sulawesi, some of the earliest cave art now in Europe, you know, the southern France cave art class example. But that kind of thing that we have, by 30,000 33,000 years ago, 40,000 years ago. Before that, and and the cave art is happening in non sedentary societies, in societies that are very mobile, they're returning to places again and again in their landscape, and they're marking them deliberately. So there, you've got that, I think, but before that, we have almost no artifacts, that Mark individuales. Now, there are ornaments. There are cases 120,000 years ago, where Neanderthals are wearing gold talents. And we have pigment marking, you know, people are gathering pigments and marking with it as early as 300,000 years, 280,000 years ago, in Tanzania, possibly as early as 400,000, in the Netherlands, right, and now I'm jumping from place to place to make clear, these are Neanderthals and modern people and the ancestors of modern people. The sorts of stuff, right, that kind of stuff, the stuff that is what you might call non utilitarian, but actually the utilitarian function of it is social communication is as old as hafting artifacts hafting points on to spirits and that kind of stuff. But it's not clear at that phase, right? If you wear a necklace, do you have religion? Do you have some kind of spirituality, some kind of belief system? I think it's likely, because I think it's sort of baked into our social cognition.
But I don't know.
Nick Jikomes 1:17:50
Interesting. So one of the the first actually podcast I did was with this guy named Brian moresco. He's got a book called The immortality key. I don't know if you've heard of it. I have, yeah, it's really interesting. I happened upon it somehow. And I read it cover to cover. And it's all about the intentional use. And this is like, you know, ancient Greece, ancient Rome, that general time period, the intentional use of people of plant material together with an alcoholic beverage, wine or beer, they're mixing these things together. And they're doing this all the time. So it was much more common back then too much more common today to have a glass of beer, a glass of wine. And back then it's much more common to take that and mix it into an elixir. So putting in herbs and stuff to make it taste good, or for medicinal reasons, or for ritualistic reasons. And so in this case, he was talking about evidence that had been uncovered fairly recently for aromatised MRI, which contains an LSD like compound that is going into the beer spiked wines that have various botanical sources of strongly psychoactive compounds. And he tells this fascinating story of what people were doing with that stuff. Yeah, but there's this larger question of, of just the ability to make this type of stuff. So what about something like beer making the ability to take material natural material, ferment it and create a beverage like that? How far back does that go? Is that post sedentary lifestyle
John Hawks 1:19:22
stuff beer making goes back? We now know as far as pottery as soon as it's pottery and grain there's beer. And so there's there's a fundamental limit, right? Is pottery isn't that old? Right? pottery goes back, you know, in Japan, it goes back something like I think 20,000 years ago, don't quote me on sort of large scale society archaeology because the details that I have her from the 1990s but but it's, you know, sort of Neolithic era throughout much of Western Eurasia. And, and yet, as soon as there's pottery we now know From proteomics, because you can sample the proteins on the pottery. We know what they're doing right and and they're fermenting really fast. They're also they're also milking and burying really fast. And so we've got amazing evidence of dairying. Now in Africa, on pottery artifacts that goes way back and in dental calculus, the other thing, right is that you carry around in your mouth, this little fossilization environment, which is the calculus that grows on your teeth. And it's plaque. And as the plaque, your body's defense against this causes it to calcify. And so it catches up, whatever is is floating around in your mouth. And that includes fragments of plants, the the phytoliths, that are parts of plant cells, the starch grains get caught up into this chemicals get caught up into this. So we actually have some, and not as much as we will have, I think we're gonna know much more about this in the future. We have some evidence of calculus, exploitation of this stuff that goes way back. The reason why that's interesting is that Neanderthals there are cases where we have clearly non dietary plants that they're using. There's a place in Spain where they're using Yarrow and a couple of other things. I think I want to say whatever is there, oh, Yarrow is a plant that you might have seen in a garden. It's got a yellow flower, and sort of ferny light green leaves. And it's used in large, lots of the world in traditional societies as a medicinal plant, including North American Indians and and in Europe historically. So yeah, it was a big one. ephedra, I believe they've got in some ancient remains. And so yeah, a federal presumably that's
Nick Jikomes 1:21:59
like ephedrine,
John Hawks 1:22:01
yeah, yeah. Yeah. So yes, it's, it's well known in Chinese medicine. But but it's more widespread than that. So there is some good, there's a good source of evidence about this kind of thing. Now, the evidence is spotty. Because the work is is you know, only right, they've been doing this kind of work now for since 2007, eight, so maybe 12 years. And there's some really cool stuff that's come out of it. But it's like everything, you know, developing the methodologies, you find more and more stuff.
Nick Jikomes 1:22:37
Interesting. So sorry, teeth are really these great reservoirs of information. And this is a relatively new field. That sounds like you're set, you're saying?
John Hawks 1:22:47
Yeah, absolutely. in anthropology, we used to hate calculus, you know, because it obscured the details of the teeth. And after all, you go to the dentist and pay them to take it off. So it can't have any use. But, in fact, it is this sort of natural, natural preserve preservation environment, for your oral microbiome, right? We've got complete bacterial sort of communities from ancient calculus, and diet and other things that you're using. And so yeah, they're at the moment, the earliest evidence of non dietary plant exploitation is coming from this stuff from Neanderthals. Interesting. So
Nick Jikomes 1:23:29
as soon as there's pottery, there's alcohol, and there's milking pretty much. So we've sort of slowly marched through time, sort of, and now we've got sedentary humans, they're making pottery, they're making alcohol and milk. And your mention of milking reminded me of something I wanted to ask you about, which is the very recent evolutionary changes our species has had, genetically, and what might be in store for us in the future. So I think there's a there's a notion probably in the average person's mind that humans have stopped evolving, because we are no longer worried about getting eaten by lions. Were not under the selection pressures that a wild animal or ancestors were under. So starting with the lactase persistence phenotype, can you maybe talk about some of the recent evolutionary adaptations of humans and why we're not actually done evolving?
John Hawks 1:24:23
Yeah. So over the last now, 15 years, right, the Human Genome Project happened. And after that, the first priority was to sample more genomes. Because it's not only important, which order the genes are in that for one genome, you get that it's also important how people vary. If you want to find connections between genes and disease, or genes and any kind of traits you need to know variation. And as soon as variation started to be sequenced in lots of populations, it became clear that you had genes that stood out as having changed really rapidly in the recent past. And that pattern is really distinctive. One of the first of these to be really noticed and measured was the lactase gene. lactase is an enzyme that helps us to digest lactose, which is the sugar in milk. And everybody has lactase. And that lactase is essential to being a baby, and being able to drink breast milk, right. So everybody needs to have it. There are people who are born with mutations that the activated, and that's a serious situation, and you have to supplement baby's diets and real special way. But historic prehistorically. And and through most of our evolutionary history, and most of the evolutionary history of mammals, it's natural to stop making this when you get to be a certain age, because you're not drinking milk anymore. Milk is baby food. And so adults, it's totally normal to stop producing lactase. And then if you drink a lot of milk, it can create digestive issues, because the bacteria that are digesting at our fermenters, and they're creating lots of gas, and it's unpleasant, etc. So, so we've talked about lactose intolerance. lactose intolerance is normal and natural, that's the way that everybody should be once was. And yet, in some societies within the last, really 8000 years, mutations have enabled a small fraction of people to digest the milk Add older and older ages. So there are regulatory mutations that we know of five of them in human populations at the moment. One of them is common across most of Eurasia and most of Western Eurasia from India, to Ireland. And, and one of them is in the Arabian Peninsula a good bit and also in Sub Saharan Africa and the other three are all African in different populations that have kept dairy animals. They're not universal where dairying happened. Right? Mongols have milked horses for 1000s of yours. And and their ancestors have and and the the fact is that lactase persistence is not a common genetic change among them. We can live with milk in lots of ways fermenting It is one of the big ways and so kumis fermented mare's milk is a really sophisticated cultural strategy that enables people to get the energetic content out of milk without dealing with as much lactase lactose. But these mutations after they happened, became common in some populations, and today are super common, right? In some places, the the Northern European version of this is, you know, 80 90% in some parts of northern Europe, from a new mutation 1000 years ago. So we're talking about an evolutionary change that has unfolded in the span of something like 30 or 40 generations.
And it's totally new. So that's a great example, there are others like this,
Nick Jikomes 1:28:10
what are some of the other ones?
John Hawks 1:28:12
It turns out that most of the genetic changes that make Europeans and northern Asian peoples lighter skinned, are relatively new genetic changes, not all of them, we know that they're something like 25 genes that affect skin pigmentation, hair pigmentation, and some of them are old polymorphisms. They've been around for a long time. And and remain variable in Africa and and other populations in the world. And I've been selected in in northern populations. But But some of the changes are very new, less than 20,000 years old, and have become very common. One of those is a gene called SLC 24. A five a new mutation has gone from being new to being 95% in some parts of the world, within the last 20,000 years. There are disease defenses that are part of this recent evolution. So malaria defenses are some of the best known of these. You've got lots of populations around the world, especially tropical places that suffer malaria as an endemic disease. You have in those places, mutations that help people to resist malaria, and most of them are new. sickle cell mutation is something like five or 6000 years old. There's a blood type. That is a rare that is a that's not one that you get typed at the doctor, right? It's not Abo but it is called Duffy and the Duffy no blood types, the people who don't produce the product that is displayed on red blood cells that have the Duffy antigen, that that blood type is really Common in Sub Saharan Africa, it's up to 95% in some places, and is about 35 40,000 years old. And so you've got these sorts of really rapid evolutionary changes. And 40,000 years is a long time. But we are talking about a new gene that has gone from one new mutation, to being in 95% of people in, you know, something like 1000 generations, that's really fast in evolutionary terms. And so this phenomenon of our population has evolved, it is evolving really fast. And some of the differences that we think, you know, are highly visible today, like skin pigmentation is actually totally new. The differences in skin pigmentation didn't occur between ancestral populations that we that we recognize 50,000 60,000 years ago.
Nick Jikomes 1:31:00
So the the immune system is really interesting that it's pretty intuitive that the immune system would be a sort of rapidly evolving area of the genome, that maybe this is still happening quite a bit today. You mentioned towards the beginning, that actually some of our Neanderthal genes had an impact on COVID susceptibility. Can you talk a little bit more about that? What was that susceptibility? Exactly? And are there certain populations of people today that are more likely to have those genes?
John Hawks 1:31:29
There are populations, you're more likely to have them? And I haven't actually read the new paper to be sure exactly which ones. We do find that Neanderthal genes that that persistence days, people, sometimes, on average, they are very rare, right. And the average Neanderthal gene is less than 2%. But some of them have become common in one place or another. And some of them are up to 60 70%. In some populations. The COVID story is one that we're still that scientists are still I'm not I don't study COVID. But a lot of people are trying to understand, mainly because they're trying to figure out how COVID works. And with these genetic changes, a lot of times it's that you sort of I could say lactase, and lipase is a great example. Because we know what it does. There's no mystery, if you don't make it, you don't digest lactose. But with most things, it's totally mysterious. A good example, is a gene called er, e da er, er has one major effect that is really noticeable. It tends to thicken the shafts of hairs. And so and it's very common in East Asia and in American Indians. And so the straight thick hair phenotype is one that this gene is associated with it. Okay, that mutation that that has that phenotypic effect is relatively young, it's happened something like 30 40,000 years ago. Okay. It's selected. It's common in one part of the world, it's relatively young. We know one phenotypic effect. What does it do? Why is it there? Right? The answer is we have no idea. We don't know whether it has other phenotypic effects that matter to survival and reproduction, whether the hair form was itself the target of this. It is, it's a big problem, actually working out why genes matter. And it's that way with the immune system, almost more than anything else, because with immunity, it's never obvious why the genes actually work. with malaria, it's not even immune stuff, right. with malaria. Most of there are HLA types that matter to malaria and Abo matters to malaria. But most things are just blood cell stuff, where the way that you fight off Malaria is break it breaks the blood cell. Make it not work, right. That's why would we name these things as things like sickle cell and melanesian, ovolo cytosis, and G six PD deficiency, which is not blood cells, but a different chain. But these things happen to disrupt malaria infection, because they make your body broken in microscopic ways. And so the malaria doesn't work anymore. That's not ideal. You know, that's sort of that's actually the worst case. But a lot of times, that's what works with selection, like selection, if it's going to take selection takes variation that helps survival and reproduction. And it doesn't matter if it's optimizing. Right. In fact, optimizing is a rare solution. Usually, it's Do something. And if that something helps you to get over a bar, it's selected.
Nick Jikomes 1:35:07
Interesting. So earlier, I want to talk a little bit more about your work in particular, earlier, you mentioned the rising star cave in Africa. Can you walk us through a short version of that story? How did you how did you come to be involved in that? And what what did you guys discover there?
John Hawks 1:35:24
Sure. So this is my good friend Lee Berger, who's National Geographic Explorer, and also a profit the University of Witwatersrand in South Africa. He and I began working together in 2010 2011. And in 2013, he was working on survey of some of the cave systems in the area outside Johannesburg, South Africa, this is an area that's part of the cradle of humankind World Heritage Site. And he had some guys who were cave exploring, and and these guys, Steve Tucker and and Rick Hunter, went into the rising star cave system. It was not an unknown cave, you know, his cave they were familiar with. But they found a passage that they hadn't noticed before, it was not a map, when they emerged down the passage way where there was a drop of about 40 feet that they climbed. When they emerged into a chamber underneath there were bones. And, and so those bones prompted an investigation. And in 2013, we came on site, a team of folks and began to excavate in the cave. This is a really cool team enterprise, I have to say, right, and part of what's important about it, is that the chamber where we began working, the dinaledi chamber, is totally inaccessible to anybody that cannot fit through a seven and a half inch gap. And so you have this sort of real real constraint. And it's not only that, but it's a, it's a gap that's in a sheer rock climb, that you have to have some pretty advanced climbing skills to be able to navigate is this because the cave went through some kind of erosion or change at some point? It's a, it's a great question. And I can telegraph the answer to it, it's that when the hominins, were using this cave system, that drop was very much the same as it is now. So their bodies entered the chamber in the way that our team does, it looks like we also since that time, have found additional hominid remains in other parts of the cave system, including a really nice partial skeleton of this species from from another chamber. So we've got their bodies, we've got them in the cave in abundance. And when I say in abundance, we are now on, I think, 2500 fossils of hominids from the cave system. So we have a really, really large assemblage of this hominin it's not human. And it's different from us in some really extraordinary ways. It's an upright low Walker like we are, it has feet and hands, which are very human like its skull looks like some kind of extremely early form of argenis. You know, something like Homo habilis, it's brain is about a third the size of that risk. And its shoulders and and forearms look like they were pretty good at climbing. There's other kinds of details about them, but but what's kind of cool is that we've got a lot of them. And so we know something about their population, we know that they lived there about 250,000 years ago. So they're living there at the time that our species is getting going. It's originating, and we have no idea at the moment, how they might have interacted, or, or, you know, we didn't expect to find them. And now that we found them, we don't know how they survived.
Nick Jikomes 1:39:17
So but just to be clear, you're saying it's extremely difficult to get into this cave. That cave has always been that way. And so the implication is that these individuals, were going into the cave on purpose and putting bodies there.
John Hawks 1:39:34
That's what it seems like, we have what we can show and we try to, really, I have to describe the science, right? Because we could say, well, it looks like that they were, you know, using this as a burial chamber. And in every term that people would recognize, that's, you know, that's perfectly accurate. But to be really precise, right? Because we use forensic methodologies and we try to really work out what's going on here. We know that we have their bodies in chambers in the cave system that are 140 meters apart in the cave, in total darkness, you can't get from one to the other without navigating dark passages. We have bodies in abundance in in a situation that could not have accumulated as a pile all at one time. We have no evidence of any other. Any other mammals interacting with them, we have a few bird bones. And we can't place whether the birds were there at the same time. We have nothing other than these hominids, we don't have an assemblage of tools. With the hominids, it's clear that where we have found them was not a living site for the hominids, they were not using that with, you know, refuse from their meals, they were not carrying other stuff into it, that we found anyway. They weren't manufacturing tools there. They seem not to have spent a lot of time there.
Nick Jikomes 1:41:10
So no cave, so no painting or anything like that.
John Hawks 1:41:13
Nothing like that, that we have identified. And and so we know that they were using large parts of the of the cave system that were in the dark, we know that we found their bodies there. And we have no other means of having their bodies transported there other than somebody put them there.
Nick Jikomes 1:41:35
And does this mean that they must have been able to use fire to see
John Hawks 1:41:40
we think that's very likely? Yeah, we think it's likely that they did. And that's not very surprising, really, because we do have evidence of fire in the archaeological record that goes back well, more than a million years. So we know that there were fire users and the fire users that there were were prominence that had brains much smaller than living people that they were they were early evidence in that sense. So fire is not a barrier in that sense. But at the same time, it's not easy to find evidence that they made a fire in this place. So so I can't say, Oh, yeah, we've got the here's the fire that they lit. They don't have that. I think that they use fire.
Nick Jikomes 1:42:27
And I still excavating the site is still all ongoing work.
John Hawks 1:42:31
Yes. So what we know so far really comes from very limited excavations. And they will remain limited, we are not intent on on really exploiting the entire site, we do have skeletal remains that we're still studying that represent, you know, really interesting things within the sample. We have, we've taken a bunch of we've taken a feature out of the cave system that has skeletal remains and miletti inside of it, that we've plaster jacketed, and we are going to study those virtually and leave them sort of an undisturbed. So we've got a lot of work ahead of us. But but it is a really fascinating discovery because it's unexpected. It's an unknown hominid from a place that we thought we knew really well. It tells us that there was much more going on in Africa where our species originated than we suspected. Right? Our record of it is actually very sparse. We don't know everything that was there. And one of the real clues we're getting from genetics of today's people, right, I mentioned that ancient DNA is something that in Africa is not going far back, because it's not the situation isn't good. It's not cold, it's not dry. But we do have increasing knowledge of the genetic variation of today's people, because of genome efforts sampling and and the kinds of sampling that we're doing for human genetics. And one of the things that has emerged from that is that African peoples have DNA that comes from some ancient branches that are as old as the Neanderthals. And very much like the Neanderthal case where we have maybe 2% of their genetics. People today have maybe 2% of the genetics of some other ancient groups. We don't know who they were. And it's possible that maybe the lady is one of these groups, or maybe it's not right, it could be totally different things. But the the import of that is to say that our evolution at that stage was much more complicated than that we can see today with the archaeological record. And that's a world that we have to get into an explorer more. Because as we've shown, right when you are exploring and you're finding stuff, it's stuff you didn't expect to find.
Nick Jikomes 1:44:56
So Around this time, I mean, you sort of touched on it a little But Around this time, if we could go back in a time machine and walk around Africa all over the continent, how many distinct species or semi distinct species of humans were there? Is it a few? Is it dozens and dozens?
John Hawks 1:45:15
I would be surprised if in Africa, we did not have 10 or 12 of these. And in other parts of the world, right, I mentioned right, with Nana atolls, we have another branch that are distant relatives of the Neanderthals, called the denisovans. That we now know, we're diversified because different peoples in Southeast Asia in China, in in East Asia more broadly have different denisovan populations that they've interacted with. We have Homo floresiensis, we have Houma Luzon, ANSYS and the Philippines. Right, you start to list the ones we know about, and you get a half dozen. And I believe that we probably have not get half of what there was. So I would not be surprised if we went back in time. 200,200 50,000 years ago, before modern humans became the wave that eventually have inhabits the entire world. I think that there probably were 20 Wow, populations is different from each other as as we are from Neanderthals, or more or more. And that diversity, right? It's, it's maybe not surprising, right? If you just look at Central Equatorial Africa and say how many kinds of chimpanzees are there? There's four really genetically differentiated subspecies, they're as different as we are from the turtles. And to and what and bonobos, which are different species there is different from from common chimps, as we are from homeaway rectus. And there's a ghost population of of bonobos, or chimps that interacts with bonobos and gives them some of their DNA. Right. So we're looking at six known subspecies species of chimpanzee like creatures in the space of Central Western Africa. And so I think that hominins are not unusual. I think, actually, this is probably the population structure that you should expect. Yeah, it's just that we haven't really been able to measure it yet.
Nick Jikomes 1:47:30
I mean, it's sort of wild to think about is in terms of, you know, when you look around the world today, humans, right, we're weird in many ways. One of them is just we walk on two legs, and we talked about bipedalism a little bit. But you're saying that there could have been dozens of species of humans walking around on two legs, most of them at the same time, and they probably looked different, acted different, and could interbreed with each other. And did
John Hawks 1:47:53
yeah. And we have such a skewed vision of this. Because our perspective today is so used to thinking about about race and races. And what we see around the world today, our variation today is minuscule. It's just tiny, compared to what we're talking about in this past time interval, right? Today's races are so similar to each other, that the differences that we observe between them are really superficial. They're they're really dominated by these few genetic changes that are recently selected. And when we look at Neanderthals and populations that once existed, right, were actually, right, our shared ancestors, among all the races of the world today, our shared ancestors are dense, and go back a maximum outside of Africa, of 70,000 100,000 years, right, where we talk about Neanderthals, our ancestors go back 700,000 years. And so there's a huge difference that that is just evaporated, except for the echoes of it, that are still there inside of our genomes that give us a little clue of the diversity that was lost.
Nick Jikomes 1:49:10
So it seems like the story that has emerged in the last few years compared to decades past and our understanding of human evolution, is that I want to choose my words carefully. So correct me if I'm if I'm misusing them, but that interbreeding between these different types of humans was much more common than than we once thought it may not have been common in any individual place. But anywhere there was an opportunity for some interbreeding between the Android cells and humans or other forms of humans and modern humans. It likely was happening to some extent.
John Hawks 1:49:45
Yeah, there's a tension in evolution between interbreeding gene flow and differentiation, you know, genetic drift and selection that makes things different. They act in different directions. We've known this right. And we know that that balance works out differently different species 20 years ago, people arguing about what was the pattern of human evolution? The fundamental argument was, is this like the origin of a new species, modern humans, that spread throughout the world and drive everything else to extinction. So you've got these very different things that didn't interact very much. And one of them spreads replaces the others, or are these possibly interacting, right? There's gene flow between them. And that gene flow is happening more or less continuously. That was a debate. Right? And and what we know today is that well, neither of those is really the picture in the picture is there were events that caused one of these groups at one time, maybe another one another time to rapidly expand and grow and displace other populations. But when that happened, they interacted. They interbred, and genetics from one from each of those populations tended to influence the other to some degree. But those groups were way more different than what we think about today when we think about human groups, right? They were they were as different as chimpanzee subspecies are from each other. Maybe as different in some cases, as chimps and bonobos are from each other. And, and those, that tension of, yeah, they became really different. And they were doing their own things. Oh, but then later, they got together again. And, and sometimes it was bidirectional. So the Neanderthal is a great example, because the first genetic sequence from the Anatol came from the original neander Valley, skeleton. And it was a mitochondrial sequence. And this is in Germany, right. So so right outside of Dusseldorf, there's this valley, and it's called the Neanderthal. And, and that's where the first Neanderthal was found. And the first genome seen the first genetic sequence was on that specimen, as fun tape haibo in his group in 1997, they get this and they show the mitochondrial DNA of the Neanderthal. And it's not like anybody living now, nobody has this anymore. And so Wow, the Neanderthals are gone, you know, that extinct. And today, we can see that early Neanderthals didn't have that mitochondrial type, right, that mitochondrial type that later Neanderthals had shares an ancestor with, with yours and mine and everybody else's living today, about 450 500,000 years ago. And earlier Neanderthals have a type that differentiated from yours and mine and everybody else's, and the later Neanderthals, something like a million years ago, what happened? What happened was that Neanderthals went along their merry path evolving. And at some stage, some Africans came up, or some Neanderthals went to Africa. And they interbred, and they carried to Europe and other places Neanderthals live the African mitochondrial DNA type. And replaced what was there before. And then later, those Neanderthals again encountered the descendants of those Africans, which are, which are our ancestors, and interbred with them again, and their mitochondrial type didn't make it this time, but other genes did. And so you have this kind of, it didn't happen all the time. But it happened, enough to see enough. And the weird thing is that we have this cave in Siberia Denisova cave, that's tremendously interesting in lots of ways. And I've been fortunate to be able to visit there and see the work there a number of times. The Denisova cave is famous because of this group that needs events that we've really only know about from genetics. But it's the densest DNA preservation of any site that we have so far going on. And one of the things that's found there is a tiny bone fragment that represents a person who once lived, who had a Denisovan father and a Neanderthal mother. Right, so So this person's parents came from populations that had differentiated 500,000 years before. And
there they met and had a baby. And here was this person, a hybrid. Now, hybrid is a way to term right because we think of hybrids, you know, in Wisconsin, We think of hybrids and we're thinking corn, you should write because hybridization is something that's between very different lines. And you tend to think of that as being exotic and strange. And it's sort of maybe should be considered to be exotic and strange. We do mean that term to mean, eating between things are very different. But this is happening a lot in human origins, it's a part of our story. It's shaping a good fraction of our genomes. And, and that that story is something that was totally invisible to us 1015 years ago, you know, it's just transformed the way that we look at things.
Nick Jikomes 1:55:42
So one of the questions here that I have is the the nature of the interaction when there was interbreeding between the animals and modern humans and other populations. So when you think about historical time for humans, and the way that different groups tend to meet, and how they tend to interact, there's many different ways that happens, sometimes two groups meet, and there's a friendly interaction, and people fall in love, and sometimes it's not as palatable. So do we know anything about how friendly the interactions may have been between these different groups?
John Hawks 1:56:18
Yeah, I, I consulted for a documentary once. And they all want to know the answer to this question, right? Because they have to hire actress to do it. And so the question is, right, is this quest for fire? Or is the clan of the cave bear? Or, you know, what is going on here? And the answer is, we know, ethnographically, right, I look at the richness of what we know about human societies around the world, and the interactions that we have with different cultures. And in cultures that are in contact, right, because we're not talking about a group of Africans that come 3000 miles, and meet Neanderthals for the first time, because they've been walking across the desert, you know, that's, it's small groups that are interacting with their neighbors at all times. And sometimes those range expansions, and they, you know, encounter somewhat different neighbors, you know, and those interactions go on for hundreds of years, between groups, and for 1000s and 1000s, of years between sort of populations. So, I think that, that you can read literature, right, written in person, you know, first person perspectives of culture contact, in historic cases, right, and historic cases, with small scale societies, historic cases, with large scale societies, and the range of what you see, people fall in love, you know, they, their parents try to convince them, their families won't let them won't let it happen. But they're in love with each other, right? Or one group conquered the other. And, and captives were taken, and they were slaves initially, but eventually, they were integrated into the society, or their, their, their offspring were, or they didn't really know each other, they encountered each other somewhere, and then they made it, and maybe they never saw each other again, you know, and, and you just think of all the different ways, and you most of us have read in fiction that has these kinds of things in it, and nonfiction, right. And the nonfiction is important because, in fact, human experiences cover this entire range of interactions. And I really believe that, that this is what it was for humans, for Pleistocene humans that were interacting. You know, we're not talking about apes, you know, we're talking about people. And those people had human emotions, they had human feelings, they had human intentions and desires, but also human fears. And, and all of those things, I think were part of the interactions. So sometimes these were very happy stories, right? Sometimes it was, you want to make the movie about that. And sometimes it was not happy. Sometimes it was horrific. and everything in between.
Nick Jikomes 1:59:24
Yeah, that that makes a lot of sense. Do we know? So we touched on mitochondrial DNA which we inherit only from our mothers? Do we know anything about the directionality of influences in terms of sex? So for example, did it tend to be Neanderthal men mating with modern human women or vice versa? Or is it everything?
John Hawks 1:59:48
autism only there is there is no really clear bias in these cases. And so I think that unbalance the evidence is well it happens sometimes when Sometimes the other way, the exception of this is the X chromosome, so we didn't get Neanderthal wise, or Neanderthal mitochondria. And in fact, the Y chromosome of mitochondria and today's humans are both really constrained and variation compared to the rest of the genome. And probably this suggests that there was something that was either in terms of small population size and expansion or in terms of selection, that was, you know, favoring limited mitochondrial Y chromosome diversity. So they're not great clues for us. However, the X chromosome is really depauperate in admixture from ancient populations, right? When we look at where on our chromosomes, do we have these genes? There are deserts or places where nobody has Neanderthal genes? And those deserts are disproportionately x chromosomal
Nick Jikomes 2:00:52
x is the one that inherit from our mothers.
John Hawks 2:00:54
That's right. Well, it's the one that men inherit from their mothers and women inherit from both parents. Yeah. So. So it is sex linked, but not to the extent that the Y chromosome mitochondrial. And so what explains that this seems to happen a lot with distant meeting, you know, meeting between distant lineages across mammals, the X chromosome is depauperate, in a lot of cases like this. So the best guess about this is that when you have genetic differentiation between populations, and they come back together, that the X chromosome, the the weird thing about it is that men only have one copy of it. So if you have something on the X chromosome, that doesn't work, ideally, with everything else in the genome, it's going to be noticeable in men. And if there's selection against it, it's going to be exposed to that selection. So the concept is that this is related to hell Danes rule, where, where there's a difference in where where female hybrids are viable, and male hybrids aren't right in, in mammal hybridization. Probably this is like the first stages of that, that, oh, when you're different enough, the X chromosome sometimes has problems. And and so there is selection against introgression of genes on the X chromosome more than then in other cases. And maybe that means that these populations have become different enough that it matters. And so that is, if you want to talk, you know, are Neanderthals, a different species, same species, you know, whatever. That's the sort of evidence that we're going to build that from, you know, is observationally is, well, if they're different enough that there is a hybrid, sort of this depression, then that probably deserves being recognized as Oh, yeah, there are different species and this species hybridization. We're not totally there yet. But in terms of, what do we know about this mixture? This is one thing that we do know, we know that the stuff that went away, was disproportionately X chromosome stuff. And that probably tells us something about those initial generations after, after the mixture.
Nick Jikomes 2:03:22
Interesting. So how long have you actually been a paleoanthropologist and as your background, always been working towards that, or what was your education, like,
John Hawks 2:03:33
I was an English major. I was, you know, I really, you know, was was, you know, directed toward, you know, I was thinking I was going to be humanities guy, I got interested in cross cultural kinds of humanistic questions, and took some anthro courses, and I took a biological anthro course. And I really got into it and, and was able to be a TA for that. And so that was what really transformed me toward an anthropology career. When I went to graduate school, I went to study paleo, right, I wanted to study human evolution, I really did feel at that time, that that was going to be a very bio cultural type of work for me, you know, I sort of thought, you know, I'm interested in the origins of culture, I want to think about origins language, you know, that sort of stuff really drove me initially. And as happens in scientific careers, you discover that the questions that drive you are not really amenable to, to being solved. And so I got interested in the editor tools, I did a good amount of work on that. But really what mattered in the 90s was, this is the time the Human Genome Project was happening. It was really clear that genetics was going to be a new area of evidence that had relevance to human origins. That, that was gonna generate data much faster than fossils. And so I started working on genetics, and did my postdoc in genetics really did a lot of work with early human genome. And, and, and hashmap, the the sort of first efforts to, to get diverse samples within populations. That was what really drove me for a while. But I started getting back into the field again, and thinking about excavation of fossils, you know, really, you know, when I started working with Lee Berger, because he was making some really great discoveries. And the time, when it looks like you weren't going to discover any new fossils, which really looked like in the 90s, like I was, you ask people, you know, is this a growth area? And no, the answer was, no, we've found all the fossils are gonna be more fossils. So for a student that was really dispiriting, you know, it's like, you know, I could Trump, you know, out in the country for forever and not find anything important. That's a tough thing to be looking at. But it turned out to be mostly an illusion. The fact is that there was a lot left to find, and still remains, I would say that our discoveries are accelerating. And it's partly because these technological changes the increased attention to population differentiation, the kinds of molecular approaches people are beginning to take, has driven us to look at the fossil record in new ways, and to perceive things as important that we used to not notice.
Nick Jikomes 2:06:42
You're an English major, and then you got interested in paleo. And it sounded like you you from there really paid attention to, you knew you were interested in paleo and anthropology and human evolution, but you were willing to learn about completely new fields, as soon as you recognize that they were actually going to be the key to unlocking this pursuit.
John Hawks 2:07:03
Yeah, I mean, that was really, I think, any scientific career, you know, has to, has to you have to be light on your feet, you know, to really survive, and especially in areas like this, where, where they're interdisciplinary, you know, you rely on on insights from other fields. And the data are limited, right? It's, if I don't say, I don't, maybe I wouldn't advise astronomers in the same way. But in a sense, you do, right? Because the, because the big questions that get asked, are often old questions that you can now look at, because you have a new way of looking at things. Yeah. And I've always, you know, my, my work in genetics is today really focused on this, this idea of, can we find new ways to look at things? Because when you invent a telescope, you make new discoveries, and you don't expect to find them? Right? And yeah, we've got tremendous giant, big data samples of genomes today, can we find new ways to look at them? Can we find new ways to organize the information from them? That gives us a way of seeing it differently? Because if we can, we're gonna notice things that we aren't noticing now.
Nick Jikomes 2:08:21
What do you think, are some of the biggest answerable questions in the next, say, five to 10 years that we're really gonna learn the answers to?
John Hawks 2:08:32
I think that so much of the things that we care about are discovery driven, you know, and we can't say that we're going to discover when, you know, what happened to the last Neanderthals, or where we're, you know, the, how many of these ancient species were there? You know, because I have feelings about that. But I can tell you that it's so discovery dependent, you know, I can tell you that, that drives our strategies, in in searching for discoveries, it makes us think about the undersampled areas, and and what we have to do to explore in them. It makes us think about, you know, what resources are necessary to expand datasets. So, those are, those are big things. But if you said what are answerable questions, right, what do we, what 10 years from now? What will we know? That we don't know today? that we care to know. I think that one area that is that is accelerating tremendously, has to do with childhood and the evolution of childhood. And it's because we have a new way of looking at development. The teeth grow by growth increments, and we've recently developed methodologies that enable us to look at the isotopic concentrations and and rate of development of those growth. Comments. And that gives us insight into weaning. Very When did they stop having breast milk? And when did they start taking them outside food sources? And what were those. And we've discovered amazing things from this. Some work by Tanya Smith at Griffith University has found lead exposure in the early childhood of a Neanderthal. Right? We have no idea what was going on. But the the fact that you can now look at fossils, and say, this baby was weaned at age 18 months, and this one at three and a half years. And this one, right, that opens to a horizon to look at the evolution of development in a way that we haven't had before. And I know that 10 years from now, we will be saying totally new science, different things that we're saying, Now, we're gonna know what the distribution of weaning times was in lots of ancient populations, including hominins. And we're going to know how much has changed. And so that's a big thing that influences our view of, of how our life history has evolved. But it's not the sort of thing that the Discovery Channel is running on late at night, you know, like, for ages, we've been wondering, this is where discoveries are happening. Yeah, but it's not the sort of thing that you know, is, is in people's imagination. I think that we're going to know about distant contacts. One thing that's really cool, that's just happened in the last year, is this evidence of pre Columbian contact between Pacific Island and a Native American populations. And we know this because the genes have showed up. And they carried Native American genes back with them to Polynesia, right, well, and so that kind of thing, right, these long distance contacts between places, we're gonna have a dense record of this. The ancient DNA stuff, right, in the sense that, where we have good ancient DNA samples, we will have a dense time series of populations and migration between populations. And we're gonna know, we already have have found out a good bit of what drove the adoption of the Bronze Age, right? What happened? when people started herding cattle? Where did those people end up? We know a lot of that now. And by 10 years from now, I think we're gonna have a very finely detailed map of it.
Nick Jikomes 2:12:33
So you've got all of the genetic work, and then you've got the, you know, the physical labor that goes into excavating a cave. So when you go to a site, like rising star or any site like that, I mean, you know, we can just think of stories from our own lives where we go back to our childhood home, or we go back to, you know, the school, the elementary school, we went to, what's it, like, when you walk into a site like that for the first time and just see it?
John Hawks 2:13:01
It's, it is interesting, because, yeah, I've, I've been fortunate to be in a position of doing that a number of times. And I can tell you that different places have different feelings. That, you know, it's totally subjective. And it's in part, right, I have to perceive that I know something about the history of this place that most people wouldn't know. And it history, right, people who were there before me, didn't know. And so that gives me I don't know if it's a sensitivity to, or a fictional idea about. But it gives me a different feeling. And I can say that in some places I have, you know, I sense the, the feeling that, that there's this deep history in a place, and it's around you, and it's shaped the place. And if you only look, you know, that you're looking at the things that the ancient people, you know, did and there are places where the ancient people made the marks, you know, so, so that's now I've been in some of those places, and, and it's like, wow, you know, you could touch the marks they made, we don't touch the marks they made. But there they are, you know, and so that's, that's interesting, but I also have been in places that have this deep record, that feel dead, that feel like you know, it's like life is not here. And those feelings are attention, you know, it's like, there are places where it's like, wow, the evidence of life is here, right past lives are somehow here and it's not a you know, like a cozy feeling. But but sort of like a, you know, you're connected feeling and other places where that's absent. I don't know fully what drives that, right. I don't know that. It's not just imagination, but I can say that. I really do when I am in places think about what does it mean to be here. And I think that anybody who's encountered our ancestors, you know, I've, I've really feel a weight of responsibility in being, you know, the custodian of the skeletal remains of ancient humans and their relatives. And, and I want to do, you know, I feel a responsibility to them. And I want to make sure that their place in our story is known. And that, and that matters.
Nick Jikomes 2:15:38
Well, yeah, that's, that's interesting, I hope, at some point, I'll get to visit a place like this. You mentioned earlier, you know, that, that things may or may not be the story that will, we'll make a documentary about, and there's actually a lot of documentary films out there some that are probably very good, and some that are probably very bad about human evolution in the human story, could you maybe name a couple of the ones that you think are really good and accurate in terms of the story they're actually telling?
John Hawks 2:16:09
Yeah, it's, it's not gonna be a, you know, a random list, right? Because I have been, you know, fortunate and, and have made it a commitment of mine, to consult on a certain number of documentaries that I feel like, you know, have the potential to really advance people's understanding of the science. And, and I really do want to steer people to those. One series that is really worth a look is, is a series called First Peoples, which we made in 2015. And has five episodes that relate to the initial peopling of Africa, Asia, Europe, the Americas, and Australia. The power of that one is that it's got at that, you know, at that time, the newest science, right, which didn't today in some areas has advanced, but also made room for the voices of indigenous people, especially from Australia and from the Americas. And, and that's a rare thing, in documentaries of this kind. But I think it really essential thing, because, you know, we talking about the history of, of everyone, and the connections between people and the places where they live are deep. And so expressing that this is not just a scientific exercise, it's scientists who are illuminating and making connections with people where they are and where it matters to them. I think it's really important. a program called dawn of humanity of from National Geographic and PBS Nova was on scene I was on the site when we discovered the rising star material. And, and that is really unique when because they captured the first time that anybody saw these things. And that's something that that you don't see very much right. And, and so it's it's a really great when it's also well made, it's a good document, it tells the adventure story. My book with Lee Berger, almost human tells that story. And so that's worth checking out because it is it's up to date, it tells the adventure story really, of the discoveries of these things, but some in the point of view of the science, but but I got to tell you that more than most things, this is actually a story that has more than most things in our field. This is a story where you follow the explorers. And when you have people crawling through narrow caves, and they have their own story, you know, it, it's really compelling. And I loved that be in a position of telling that story. So, so those are some great ones. And, and I think that you always there's always misses, you know, talking about the misses, but I feel like even some of the series that that might seem like they're kind of superficial or might seem like, do have some, you know, when you see people on them that are doing the work that are doing the science, they sometimes give a window that is that is really unique. And so and so I think, you know, I've I've had some I've had some negative interactions with folks doing television, but I've had many more positive ones. And and I think that, you know, look at National Geographic at the discovery at, at PBS. And, and there's some really strong BBC, there's some really strong ones.
Nick Jikomes 2:19:44
And if people want to continue following this general area and your work, what's the best way to do that?
John Hawks 2:19:51
Well, I maintain a blog, and it's john Hawkes dotnet and nowadays it's a little a little less frequent. Only updated then then it has been in the past. But But I do cover recent news stuff. I also my Twitter account, john Hawkes at john Hawkes is is pretty good. The You know, I'm on Twitter more than anything else. The it is becoming more difficult, interestingly, to follow this stuff in the news, because the the science journalism, you know, has really, the landscape has really changed in the time that I've been doing this, you know, the decline of daily newspapers in metro areas around the country has really taken a hit on science reporting, in particular. So there's,
Nick Jikomes 2:20:40
there's less coverage, and there used to be,
John Hawks 2:20:42
there's less coverage and more of the coverage is press releases that are just being repeated. So there are some great science journalists out there. And if there's a, you know, if there's a new story, in anthropology in human evolution, usually you're going to get, you know, a really good journalist that's on it. But the way to find those is actually to sort of watch Twitter. Because when you see, you know, those of us who are in the science, he recently is active on Twitter, also, a number of my colleagues are and we're, you know, usually having conversations with each other. When you see something actually rippling through that network, then it's probably new and real. And, and that's something that's hard to get any any more from the press.
Nick Jikomes 2:21:27
Interesting. Well, john, thank you for your time. We talked for almost two and a half hours, and we covered a lot. I hope at some point I can reach back out to you because this is really an endless area of learning that you can just go deeper and deeper on. And and like you mentioned, you know, in the next year two, three, there's going to be new discoveries. So I'm really excited to follow along.
John Hawks 2:21:50
Yeah, I have the same courses that you took for me, I'm still teaching right and and what I find is that every time I teach them, the entire syllabus has to change. And that's a marker right? It's it's not that I'm changing it for changes sake. It's the fact that this is right now an extraordinary era of discovery. And and because this is an area where we have integration between different fields of science, you see that advances in one will sometimes bootstrap and leapfrog the others. And so it really does change that fast. And it is it's hard for me to keep up. I tell my students every semester, I'm learning as much as you are, and I really mean that it is it is a fast moving area.
Nick Jikomes 2:22:35
All right, john Hawkes, thank you. Thank you.