David Reich - How One Small Tribe Conquered the World 70,000 Years Ago

26:57But what's even, what's significant is that the, so humans have, to the extent that humans have had for hundreds of thousands of years, it's not clear then why humans weren't able to expand out of Africa and... We don't know that. We just know that today we have it. So it could have been only a couple of hundred thousand years ago or a hundred thousand years ago that these changes happened. But then we know all modern humans have them and modern human, different groups of modern humans have split out. Separate 200 ,000 years ago. Right. So we know it's at least that old, right? Right, right. Although there is gene flow between all groups of modern humans at least at low levels, going to a hundred thousand years.

27:34It's just most of the separation between quite some and other groups happens to a hundred thousand years ago. Let me just like motivate for the audience why this is so fascinating. First of all, it's obviously so interesting like, what happens such that 70 ,000 years ago there are half a dozen different human species all around the world that are pretty different and then fast forward to now, there's one. The fact that that happened is kind of wild. But it's interesting and just from that. But another reason it makes it interesting for me is because I talk to these people who talk about AI and what some of them have a very strong perspective that you just make the model bigger.

28:10And the thing just wants to learn and so you just make it bigger, you give it more space and it'll just become intelligent. And one of the pieces of evidence they use for this is that something something happened with human brains dot, dot, dot, bigger, dot, dot, dot, dominating the entire earth. And so that's the perspective that like you make these AI models bigger dot, dot, dot, you know, like something very powerful is going to come on the other end. To the extent that that story is accurate or inaccurate might actually have interesting implications for AI, which is sort of wild, right? Like our anthropology or genetics about to the agent world.

28:43I mean, it has like some, some lazy enough data on how well we think these AI models will do in the future. So one thing that what you're saying makes me think about and is that it doesn't map on in a simple way as an analogy. So one of them is that the human brain is maybe only three times larger than that of a chimpanzee. And that's not the kind of increase that compute ability has had since, you know, 40 years ago or something like that, which is many, many orders of magnitude increase, not a factor of three, but many, many orders of magnitude increase. And in fact, I'm aware of studies that have, for example, compared raw compute ability of chimpanzee babies to human babies, in fact, it's similar.

29:27For example, ability to solve logic puzzles is pretty similar between chimpanzees and humans. And some people argue that humans are not even more intelligent than chimpanzees at some fundamental ability to compute and that what makes human distinctive is social learning abilities and that that's where a lot of our ability has gone. Our ability to see other people, to empathize with other people, to copy other people, to incorporate bodies of information that are learned by other people. And so I am not an expert in this topic, but it's a very appealing group of ideas that the adaptations that humans have are ones that allow us to access a rich amount of shared knowledge and not just to rely on figuring out each thing.

30:09So that's not obviously the same as just add more compute ability, but maybe it has some similarities? Yeah, so I guess I still don't understand, is the answer to we just don't know what happens 60 ,000 years ago such that before humans and other, modern humans and other types of humans were interacting, but no one was in a dominant position, at least in Eurasia, and now humans, not only do we dominate, but like, in fact, we drive them to extinction. There's none of them are around at all. Do we have any idea what would change between that time? So the model that this is really outside my expertise, but ideas that have been floated and I will summarize them possibly badly, are that in every group of human beings have hundreds of people, which is the size of a band or sometimes a thousand of people, they accumulate shared cultural knowledge, shared knowledge about tools, knowledge about life strategies, and they build up a shared knowledge more and more and more, but if you have a limited size group of people that's not interacting with this sufficiently large group of people, either occasionally this group has information loss, there's a natural disaster, key elders in the group die, and knowledge gets lost, and there's not a critical mass of shared knowledge, but once it goes above some kind of critical mass, the group can get larger, the amount of shared knowledge becomes greater, and then you have a runaway process where an increasing body of shared knowledge of how to make particular tools, how to innovate, patterns of innovation, and so on, language, conceptual ideas, run a mock.

31:53So an example that I've heard talked about in this context is what happened with, for example, Indigenous Australia Tasmanians, you probably know this story, but about 10 ,000 years ago, the ancestors of people in Tasmania, which is this large island south of Australia where continuous with the Aboriginal populations of Australia, they had fire, they lost it, and they lost fire because it got forgotten somehow, and it's a cold place, and they just forgot it, the cultural knowledge lost it. So what you actually have in the world is 50 ,000 years ago is tens or hundreds or thousands or tens of thousands of different human groups, each of them possessing local knowledge, rarely exchanging with each other, when we get lucky in ancient DNA and sample them, they're quite isolated from each other, and they have reduced diversity in the last tens of generations.

32:41The great majority of them go extinct. The great majority of them are wiped out by encounters with natural disasters or other groups of humans or other animals, and so what you have is a vast experiment with an archipelago of these groups, and what might be happening is that you just have a process of accumulation of cultural knowledge and loss of cultural knowledge, but since there's many of these experiments going on, maybe something takes off somewhere, and maybe that's what happens 50 ,000 to 100 ,000 years ago. And people who all have the capacity to do these things. One thing I didn't realize until I read your book is how small the population that expanded out into your Asia was, and how small, even generally human population was, 50 ,000, 100 ,000 years ago.

33:24And I remember one of the papers you cited said that there might have been a population bottleneck around this time period. People talk about the Tobor eruption, I don't know if that's a cause, but there's many potential causes here. But anyways, I think I remember somewhere that the ancestors of everybody in Eurasia was initially like 1 ,000 to 100 ,000 people, what's to tell me how small was a human population that was like the seed of this modern period? So the bottleneck occurred by bottleneck, we mean founder event, a relatively small number of people giving rise to a large number of descendants today.

34:00It occurred well before the mixture with Neanderthals, which is probably somewhere like 50 ,000 years ago, plus or minus 5 ,000 years or something like this. So we don't know where it occurred, maybe it occurred somewhere in Arabia, maybe it occurred somewhere in the Nile Valley, maybe it occurred somewhere else, but maybe thousands or even tens of thousands of years before the encounter with Neanderthal, that's that pushed in some Neanderthal DNA into modern humans. So one way to see this is in fact, this was not an unusual thing, that this was not an unusual thing to have a group with low diversity.

34:34In fact, the great majority of African groups would have had very low diversity, and it's just the one that started expanding into Eurasia also had low diversity, but it was so successful it didn't mix with very many other groups and recharge its diversity by remixing with other groups. So maybe it also expanded inside of Africa. So there's lots of reasons to think that the expansion of the early modern human group outside of Africa would have been accompanied by within Africa expansion of the same group and that would not have been unidirectional. So one way to look at the expansion of modern humans into different parts of Eurasia where we have data is almost as a kind of sort of forest fire of some kind where it throws sparks into different parts of Eurasia and interacts with the local people.

35:20So for example, if you look at the first modern humans of African and Near Eastern origin who get to, for example, Europe where we have the best data, we have a number in Western Siberia where we have the best data so far. We have a number of these very early ones from about 45 ,000 to 40 ,000 years ago, which are called initial upper Paleolithic, and a good fraction of them have had neanderthal ancestors in their last two to four to eight generations. So that's a kind of crazy result. So we have only a couple of dozen or dozen or so of these very early humans and a very large fraction of them recently mixed with neanderthals in their ancestry.

35:57So a model that might be explained the data is that you have sparks coming out of a kind of forest fire in the Middle East of the Near East of humans expanding. They come in and they start going to places like Western Siberia or parts of South Asia or parts of Europe. They mix with the neanderthals and they produce these mixed populations like these initial upper Paleolithic groups we sample in the record and they all go extinct. Like including modern human ones. There's just extinction after extinction after extinction of the neanderthal groups of the Denisovan groups and of the modern human groups.

36:26But the last one standing is one of the modern human groups. And that's what we happen to see. And so the interbreeding event that we see, the great majority of the ancestors of modern humans, for example, in Eurasia are not from the initial upper Paleolithic ones, but from a later wave from the core in the Near East after 39 ,000 years ago that repyple a place that's been sort of affected by these sparks coming out of the same region. And those groups too disappear. Oh, that's so fascinating. So not only is a group that started 6 ,000 years ago and eventually makes us around, not only does that one not survive, but then the group that starts 39 ,000 years ago, that one is replaced.

37:05And then obviously we'll later talk about the Amnaia and like you can just keep going. Then the hunter guy there was a replaced 85 ,000, 85 ,000 years ago by the farmers coming from the Near East and then after that by the Amnaia from the step. Okay, so it is interesting that it just like group comes there is replaced by the next group. That group stays there is replaced by the next group. I don't know if that model. I think that that's probably right at some important level. I think it's not a triumphal march of superiority and inferiority with the group that now comes in having advantages somehow establishing itself permanently.

37:41I think that what you have is a very complicated situation of many people coming together and natural disasters or encounter with animals or encounter with other human groups resulting in an almost random process of who spreads or who ends up on top and other groups coming in afterward. And so it may be that from a big picture perspective you end up having African lineage is spreading into these different parts of groups, that's different parts of Eurasia, that's certainly what happened. But at a local level, I think it would be very difficult to understand what's going on. So yeah, big picture is interesting in two ways.

38:17First that you're not thinking crudely in terms of the major species or the major subgroups of humanity like Neanderthals, Denisovans and modern humans. It's like, no, in fact, even among these there were so many subcategories of different groups in the Sarcropelago and then if you do a fine grade in an Autos, that's even more fascinating than that. And how much contingency and randomness there is in that process. I think that's right. And there's lots of analogies that you have later. There's European farmers encountering step migrations. There's Native Americans encountering Africans and Europeans as they come from the Old World.

38:54There's various other groups encountering other groups. And you have people who have cognitively or culturally all the capacity to thrive in other contexts, but just because of the nature of the interaction that happens, one group declines demographically and one group doesn't. And it's just complicated. So I don't think you should conclude, necessarily it's very tempting to think that at some level it's innate biological. I'm not trying to be politically correct, that it's innate some better biological hardware that makes it possible for these African lineages to spread into Eurasia. I have no good insight into that topic.

39:33I don't think there's very good genetic evidence or any other kind of evidence to say that that contributed in a very strong way. I think that it's just complicated and we certainly have many modern examples where people with better or more competitive, cultural complexes encountering each other and the ones that are more organized in a certain way sort of thrive somehow demographically more. Yeah, okay, so let's jump forward to then, since you mentioned this, the way in which after agriculture is developed in the Middle East, I don't know, 10 ,000, 12 ,000 years ago. And then after that, the way the Native Americans, the population of Native Americans declined was because of disease.

40:22And one of the hypotheses that you talk about in the book is potentially this happened with respect to people in Europe from the Amniab with literally the bacteria that causes the babonic plague, your Sania pestis. The question I'm trying to ask is going back a bit. So James Scott, who I think just died a couple of weeks ago in his book Against the Grain, the whole book is like agriculture sucked, but we were forced to adopt it because it allowed some humans to organize nation states of their area abusive, but did allow them to get the barbarians and co -opt them because they needed the labor to do this monotonous activity.

41:06And one of the things he talks about is, well, one thing I didn't realize until I read that book is just how new all the diseases, or most of the diseases that afflict humans today are, everything from cholera to typhus to tuberculosis, if you just go down the list, and because of agriculture, because of domestication of animals, and because of the density that created. And so the theory he says talks about in the book is that potentially the reason the hunter gatherers, the quote, unquote barbarians couldn't fight back against these early nation states was because they were getting killed off by the diseases.

41:40And I don't know how much evidence there is for this. Basically, the question I'm trying to ask is, the way in which Europeans encounter Native Americans in the New World, that just happened again and again throughout history. Basically the way, if you go back to Europe 9 ,000 years ago, or 5 ,000 years ago, is that just what human history has been like? That wasn't the one off event. There's an amazing book by Kyle Harper, I think it's called The Fate of Rome, and it's an argument about the history, it's a history and Roman historian. And it's a history of three major plagues and the Roman period, a couple of which, are really not even very well known, and argues that the decline of the Roman Empire is due to just weakening as the result of plagues and other climatic, biological, climatological worsening events.

42:27And there is a lot of reason to think that some of these events have been recurrent throughout history and that it's not just difference between farmers and hunter -gatherers, but actually a lot of different types of interactions that are occurring. So the example that you mentioned is something that's been a big shock from the ancient DNA revolution. So this is now, maybe eight years, nine years old. So when the first large number of DNA sequences from people who lived five and six and four thousand years ago from the in the step north of the Black and Caspian seas and in Europe were being published about in 2015, this group in Denmark, led by Eskeweller, Sleven, Christian, Christian, and then colleagues, sequenced, looked at their DNA and they discovered in their sequence from the hundreds or so humans they sequenced that there was also pathogen DNA.

43:19And even five to 10 % of the random people they sequenced around four or five thousand years ago, there was Yersinia Pestis, which is the agent of the Black Death, but actually without the plasmid that contributes to bubonic plague that's required for flea rat transmission. So it must have been, for example, pneumonic plague, the aerosolized transmission or something. But five to 10 % of random deaths means that actually the percent of people who were dying must have been even higher because they weren't detecting everything that was there. So it's studied by another group, Johannes Kraus and colleagues of people in plague pits in London from the 1300s epidemic, found that they only, when you apply this method to people we know died of Black Death, you only find a quarter of the people.

44:04So the rate was even higher. And if people are back to Remick, when they die, when they have bacteria and their teeth, they probably are almost certainly died of that agent. So paper just came out a few weeks ago in Scandinavia, looking at these tombs from about 5 ,000 years ago of farmers who were just on the verge of countering people from the step and a huge fraction of them have Black Death when they die. They're buried in tombs in normal, even higher than five or 10%. So this whole pedigree with many, many generations, so it's not all at the same time, just like the parents generation generations, a very large fraction like well more than 10 % have Black Death and have your sinne infection.

44:46So it looks like this particular agent has been killing people for 5 ,000 years, four or 5 ,000 years in Western Eurasia. And in fact, is killing like a scarily large fraction of the population, like as a quantitative person, which I am reading this literature, I think people are embarrassed by the implication. The implication is that a third, a quarter, a half of deaths in this entire period are front this, and people are just, it's so unbelievable, so ridiculous, that such a high proportion of people over such a long period of time are dying from this one agent, that people don't even say it.

45:23They just publish one paper after the other, publishing more sequences, and they just don't think about the implications of such a high rate of death. And yet, it's really hard to imagine that people have a bacteria in their blood and they're not dying of these things. It's not, it doesn't seem that people are ignoring the, people are selectively picking tombs. These are tombs that are buried properly. They're not grave pits. So the implication seems to be this one agent that we happen to be able to detect is killing a very large fraction of people in Western Eurasia over this period. So what's the implication of that?

45:54One thing is that maybe it seems to be coming from step rodents probably, and so maybe the people on the step are somewhat more, I mean, they say it's still dying, but somewhat more protected of it, then it spreads into farming Europe maybe 5 ,000 years ago, which is when we start to see it, and maybe this results in disorganization of the population giving such a high rate of death, and maybe it creates a type of situation that the Europeans encountered when they got to the Americas where societies were disrupted. So in the last few years, we had COVID -19 that killed 1 ,5 % of the world population or something like that, and it was so disruptive.

46:31So this thing is killing a third of people or half of people, you know, randomly killing people with cultural knowledge, randomly ripping into structures like, I don't know, was it Montezuma died or one of his parents resulting in civil wars and the Enco when the Europeans encountered them, just disrupting the cultures that were there, maybe this would have created a situation where there was disruption in the old ways of life, and maybe combined with other things or even just by itself could have created an opportunity for people to move in from elsewhere, even though they were not as densely spread, because the big observation we haven't talked about, and it's something that we as an ancient DNA community have been looking into again and again now, and keep making progress on, is that about 5 ,000 to 4 ,500 years ago in Europe, there's a radical transformation in the ancestry of Europeans.

47:24An example of this is what happens in Britain. So about 4 ,500 years ago, the farmers who were there, they arrived there 6 ,000 years ago, they built Stonehenge, 40, the last big stones of Stonehenge go up 4 ,500 years ago, and then within 100 years, years 90 % of them are gone, and they're replaced by migrants from the continent bearing majority ancestry from the step north of the Black and Caspian seas. This is one place where we know what happened very well, but we see it all over Europe, we see it in Spain, we see it in Portugal, we see it in the Netherlands, we see it in Germany, we see it in Czechia, we see it in Italy, we see it in Switzerland, we see it everywhere, this wave of people from the east arrives, and it displaces these successful, impressive, densely packed farmers with new people who have this ancestry from the east, who are not as focused on farming, although some of them are, as the people who came before.

48:17This is so crazy. So, just for the audience, if you're keeping tally, this one bacteria, your stonopestus, is responsible, I mean, we learned in grade school that it's responsible for killing a third of Europeans, more recently causing the Black Death, right? And there's even theories that this helped with the industrial revolution, because it drove wages up in Britain, and because of highway just they had to make machines, and the Robert Allen, the economist, has a theory about this. So potentially causing industrial revolution. That one's more tentative. It causes inflation. So it ends, I mean, in the medieval one, creates a lot of inflation, and the surfs, as I understand it, were sort of on fixed wages, and so they had to be paid more, basically inflated out their sort of signorial responsibilities.

49:03Yeah, so that's one of many. The other is during the Bronze Age, it allows the step people basically to replace the existing hunter gatherer or farmer population in Europe. Like literally all of Europe is, allows a population from the eastern steps to, like replace the existing people who build the stone edge, but doing other things in Europe. And the Karl Harper's book talks about this, where the plague of Justinian, I think the final one that killed off the empire, was also your Sineaf SS. Definitely. That's documented with Kim. So the fall of the Roman Empire, the entire twice, or at least once, the replacement of the population in Europe, and so the second time, basically like modernity happened afterwards.

49:45It's crazy one disease, and potentially the new world as well in terms of, I don't know how many people, what percentage of the deaths in the new world were? It's estimated to be not the primary pathogen. But who knows? And in any case, I mean, there's others too, right? So some of the other, some of the other plagues in the Roman Empire are definitely not your Sineaf. So that's crazy, not only in disease, but this one in particular has had this big a role in human history. I'm curious if you can talk to, there's anthropologists and historians who have different theories about what the early history of humanity really looked like.

50:19Basically like what kind of gods did they worship? How big were the communities? What's, and this informs their political philosophy today. James Scott, obviously being the main example here, right? Can you, does genetic shed any light on whether, for example, the, in fact, agriculture was terrible for humans and the First Nation States were abusive and so forth. Or is this stuff that is not available through ancient DNA? We have indirect information about some of these things. So one thing that you might hope to learn about is whether our genomes reacted to the innovation of agriculture in a disrupted way.

50:58So you might think that our genomes would have been in some kind of steady state sort of natural selection had adapted us to the previous environments. We were in and you might expect that in reaction to a change so economically, dieterally, cognitively transformative as agriculture, the genome might shift in terms of how it adapts and so you might actually see that in terms of adaptation on the genome. You might expect to see a quickening of natural selection or a change. I don't think we know the answer yet to whether that's occurred although they're beginning to be hints and we could learn that from the DNA data.

51:35Hints in which direction? So one question is, so there's an increasing view amongst geneticists and that natural selection is a process where there's relatively little directional selection to adapt to new environments. One piece of evidence connected to this is the finding that there's very few genetic changes that are 100 % different in frequency between say Europeans and East Asians or West Africans and Europeans or West Africans and East Asians. If there had been genetic variants that had had modest selective advantages, 1 % half a percent, 2%, that's actually a lot, but over year by year, the head or risen and then that's in a few hundred generations they would have risen from very rare to very common and in fact gone to 100%.

52:23There's thousands of generations separating Europeans and East Asians and West Africans and Europeans and so on. So if that was a common process and evolution, we would expect many genetic changes to be 100 % different in frequency between Europeans and East Asians or West Africans and Europeans, we see almost none. So what that suggests at some level is that there's not strong adaptation over the last 50 ,000 years because if there was, we would have seen genetic variants driving to 100 % frequency difference across different groups around the world which have hardly been connected with each other genetically over the timeframe that we're talking about.

52:57We don't see those variants so maybe selection hasn't been important but maybe over a shorter period of time selection has quickened and variants have started rising in frequency in the last maybe a few hundred generations or something like that and we might be able to appreciate that. So maybe we could see whether there's been a quickening of natural selection over that time period. There's a question about, I think the view amongst common trade unitesists is that we've been at a kind of steady state where almost where the natural selection that does occur is just there pushing down slightly bad variants, not adapting to new situation.

53:33We're at a kind of stable point. So it's not clear how that works because over a scale of two million years we're clearly genetically quite different from our ancestors, our brains are bigger, we do some things differently, our proportions are different. And yet over the last 200 ,000 years we are not profoundly different. There's not genetic changes that differ dramatically across populations and it's like a kind of disconnect. It's tempting to think that evolution has stopped from one perspective because there's so little fixed differences. But on the other hand, somehow there are different.

54:10Somehow it looks, if you look in the last 10 ,000 years in West Eurasian DNA, which we're doing now, it looks like a lot of changes happening. So it's a very confusing situation. It feels like we don't really understand what's going on, but there's a lot to learn. Do you have any sense of what, because I've been seeing 10 ,000 years of talking about the beginning of agriculture? Do you have a sense of what the changes might look like or is it too early to tell? So we, I mean, we're working right now on a study which is documenting changes over the last 10 ,000 years in Europe and Western Eurasia, based on tracing changes in about 8 ,500 high quality DNA sequences from people from this period that has been collectively accumulated by us and others.

54:49So we've been working very hard at this, led by Ali Akbari in my group. And we think we have many, many hundreds of places where there's been very strong change and frequency over time, where we're confident of. And we think there are many thousands that we can see traces of. That is, the whole genome is seaving with these changes in this time of period. In the end of a sneak peek on, do we know what phenotype, any particular one's corresponding to? So it's very clear that there is a extreme overrepresentation of change on variants that affect metabolism and immune and immune traits. And so if you look at traits that we know today on affect immune disease or metabolic disease, these traits are highly overrepresented by factor of maybe four in the collection of variants that are changing rapidly over time.

55:55Whereas if you look at traits that are affecting cognition that we know in modern people modulate behavior, they are hardly affected at all. That is, selection in this last 10 ,000 years doesn't seem to be focusing on average, on cognitive and behavioral traits. It seems to be focusing on immune and cardiometabolic traits on average with exceptions. But on average, there's an extreme overrepresentation of cardiometabolic traits. The immune thing makes sense obviously more diseases. In what direction is the metabolic? So one example of this is that there's a very clear downward selection against body fat and against predisposition to high body, medicine, dex predisposition to what today manifest itself as type two diabetes.

56:45So that genetic combination in West Eurasia has been pushed down again and again over the last 10 ,000 years under the pressure of natural selection without a doubt in its action on many, many independent genetic variants, all pushing in the same direction in an overwhelmingly statistically significant way. So one possible interpretation of this and this is speculative is that you're shifting from a mode of survival that's more feast and famine to one where food is more regular and it's not as advantageous to store fat. And so there's selection against sort of fat storage. That's what I used to point against the narrative that agriculture was terrible.

57:26And if there had to be selection against storing fat, that seems to suggest that in fact, yeah, things are must have been pretty good. Well, on a time scale, I mean, selection acts, I don't know how you think selection acts, but at some level, it could be terrible on the individual level and good on the population level. So I think that, I'm not doubting the evidence that you're, I think, maybe referring to, which is that skeletally, there's a lot more sort of skeletally unwell people associated with the beginning of agriculture than there are in the hunter -gatherer period. And I think on an individual level, life could have been experienced more harshly, but in terms of survival, people have different animals have strategies of investing less than their young, but having many more young, or investing more in their young and having fewer young, and maybe the hunter -gatherer strategy might be the latter, and the farmer strategy might be having more young and some of them survive longer, or some more of them survive.

58:28And on average, over a lifetime, there might be a stable enough food that if you don't rely on such adaptations, it might be better. Hey everybody, here's a quick message from today's sponsor, Stripe. Stripe is how millions of businesses accept payments, build customers, and move money. That includes some of the world's largest companies, Amazon, BMW, Merriott, and it includes some of the world's smallest, like, of course, my podcast. And it is indeed true that I use the same payments method as Amazon. The reason so many companies decide to use Stripe is because moving money is surprisingly complex.

59:04Every country has its own regulations, its own payment methods, and how people want to pay in Japan is really different from how they do it in Sweden. Stripe solves all of that. They can let customers pay however they want to pay, a credit card in the US, picks in Brazil, even crypto. That obviously means higher conversion rates and as a result, more revenue for you. Anyways, you can go to Stripe .com to learn more, and now back to David Reich. So one thing I'm very curious about is, whether we have any sense of what it looked like when different populations came into contact with each other, because in many of these cases, you're talking about 90, 95 % of the population being replaced, to the extent that sometimes you refer to them as ghost populations, because only in the aftermath with this modern genetic technology can we even tell that there was some other population here.

59:52We can see the trace of that. And, you know, for example, like the Yamnaya, like when they're coming into Europe, I know there's obviously many different cases and many different cases look different in terms of how violent was or what the clashes look like, but the fact that, for example, the Yamnaya, if you focus on that one example, replaces, like becomes a dominant group in so many different parts of Europe. It's not like Jenga's Con, where it's like one empire, and there's the great con who's like everybody's, everybody's pledging field to each other. So they're not organized in that way, but like they're still organized enough that they can go from place to place, and we are the Yamnaya and we're taking over.

1:00:38Like what did that conquer that they look like? Yeah, so that's super interesting. And I'm gonna back up a little bit because in my book, I have a section where I describe when we had these findings for the first time in the conversations we had with archaeologists on about these findings. So ancient DNA has been very disruptive to conventional understanding of the past. And what happened when we had these findings of massive disruption of the local population in Germany, about 45 to 4700 years ago, based on arrival of people from the steps north of the black and caspian sea, was some of our archaeologist co -authors really just were very distressed by the implication because after the Second World War, there had been a reaction where people said this initial idea that people had based on archaeology where in the beginning of the 20th century, when people would see new types of pots in a certain layer of the excavation, they would argue that this is the arrival of a new people coming through invasion or through movement into a region, and it's very disruptive event, the arrival of the corded ware complex or the arrival of the bell beaker complex or something like this.

1:01:50This is a very disruptive event mediated by invasion or so on. And that was used by, for example, the Nazis to argue that these were spreads of Aryans moving across the landscape and being very disruptive and violent, for example. And the reaction after the Second World War was to say we don't know this. And in fact, when you see the arrival of new types of material culture pots, for example, or tools or ways of organizing life, but you might be seeing is more the spread of culture. You might be seeing, for example, something like people copying use of a cell phone or something like this, which can be used by people of very different backgrounds, and it's just or a new religion spreading, and it's not actually movement of people.

1:02:33And in fact, how could there be a big movement of people? You're looking at densely settled Europe with well -developed agriculture. How could it be that new people coming in from outside will unseat these people, disrupt these people, especially after a period of stasis, after a period of, especially once, especially once when you have farmers who are densely settled and how could these be pastoralists coming from somewhere else? They're not as dense on the ground in India today. The British were sort of in control. The Mughals were in control for hundreds of years, but made hardly any demographic impact.

1:03:07How could people from outside with less density make much of a demographic impact? But then you look at the genetic data and there's a 50%, 70%, 90 % population disruption. You take the DNA from people after these events and almost all their ancestors are from far Eastern Europe, right across most of Europe. And so the DNA proved that that idea was wrong. It was very disruptive. So the question that you add is, what does it look like on the ground? And so the DNA results was extremely disruptive to people in archaeology who made these arguments that change wasn't possible in this very large -scale migration, large -scale disruption, probably didn't occur in the past.

1:03:48And so it was a real challenge. It was a real challenge to our understanding of history. It was sort of a case example, a prime example that's been important for me in showing that we really don't know what the past was like until we actually look at it and have hard data telling us what it's like. Our guesses, our models, are including many of mine are likely to be wrong because we can see that because when we have hard data we're surprised. I'm sorry for that long preamble. So when what's happened in the last few years is there's been something of a reconciliation after the book. Archaeology is trying to reconcile itself with the DNA data and it's arguing about the subtlety of these interaction events.

1:04:26So people talk about what's happened in Britain, for example. Well, maybe the arrival of the Beaker phenomenon, which happens about 4 ,500 years ago, maybe it's not on the invasion, maybe it's a kind of peaceful event, maybe the previous people, the reason we're seeing such a disruption is the previous people we know they cremated their dead and the Beaker people buried their dead. So it looks like a much more abrupt change than it did. Maybe what happens in Iberia when there's a 40 % arrival of these foreigners from the East and 60 % local people, but the Y chromosomes are completely replaced.

1:04:58So the local men don't sort of contribute their DNA to local later populations. It looks to you, it looks somehow like that must be extremely disruptive to the local male population. But people are saying, well, maybe this is female mate choice. Maybe this is somehow kind of not what you think it is, maybe it's not what happened 4 ,000 years later amongst the descendents of the Iberians and the Americas, where today in Colombia, 95 % of the Y chromosomes are European, 95 % of the mitochondrial DNAs are Native American. We know what happened there. It wasn't friendly, it wasn't peaceful. It wasn't nice.

1:05:31But maybe what happened in Iberia 4 ,000 years ago amongst these ancestors of people was much more peaceful, was much more calm. If you look at detail in Iberia, what you see as the period of this change is actually over 500 years. But if you look at a micro scale, not that we have better data, it's immediate each place. So in southern Spain, it's very fast. And then in central Spain, it's a little later, but very fast. And so actually, there's these rapid changes occurring in one place, another. People thought in Britain, maybe this was actually a slow process. But we now have data not yet published from the Netherlands, which is clearly the same population of beaker people that's spreading in Britain.

1:06:07And there it's very disruptive. And you actually have the whole series of people before and after. You see that earlier, corded where people are local, which is actually very unusual for corded where, they're actually local people adopting the religion of the corded where, but mostly local ancestry. And then the beaker arrival is incredible disruption. There's almost no continuity, very little continuity. So probably what's happening with the beaker individuals is one way or the other, you have some kind of people who expand demographically and displace people somehow, rapidly displace people over a period of well less than a century.

1:06:44And do we know whether they were organized, because more modern versions of this, when Cortez goes over the new world, he's like serving field to the emperor of Spain and so forth, or they're like, I don't know, the Mongols and Jinguist Khan or something. In this case, I assume there wasn't enough hierarchical organization that something like that was available, but there was enough organized, I don't know if it's organized the right word, but there was enough sort of persistent invasion that we're going to keep going town to town, settlement to settlement until we've reached the ends of Europe.

1:07:18And so was it just like the Yamnaya where just lots of different independent groups that were doing this at the same time, or was it like, how organized was this basically? What do I mean to ask? So we don't know. And I think there's debates even about that. I think one example I've heard archaeologists I work with, think about is the Comanche in the US Southwest, where it's another horse -based expanding group, and they expand super dramatically in parallel to the Spanish expansion and alongside the US expansion before encountering the US, sort of militarized United States at some point. And it's local, there's local bands of people expanding, they go on campaigns, they expand to certain areas, it's the beaker people and the courted -were people, they're contemporary to ancient Sumer and a lot of the Egyptians that we actually have written history from, it's not so ancient.

1:08:20They weren't writing, but they were contemporaries of these people not so much far to their south. So we really don't know what was going on, but if you were part of a community where there is a culture where, say, the males, as we think from reconstructions from Indo -European myth, which is probably the class of cultural share knowledge, these people were operating from, because we think these people were the spreaders of Indo -European languages in this part of the world. If you think about this as a world where, at a certain age, males would band together and go on raiding parties and so on, and that would then maybe settle down later in life, you can imagine a process where built into the culture, you have a process of expansion, exploitation.

1:09:01One thing that's really interesting that has actually emerged in the last years and was not really sort of strong at the time that I wrote my book was an understanding of the relationship between the Yamnaya and groups like the courted -were and the beakers. So the Yamnaya are these groups that thrived between about 5 ,300 and 4 ,600 years ago in the steps north of the Black and Caspian seas. They're probably the first people to domesticate the horse, or that's arguable, and they use the horse in the cart, which was newly invented in the wheel, to exploit the open steplands and be able to economically expand much more rapidly.

1:09:41They're the world's first extreme mobile pastoralists, but they can't get further than the step. So they expand into Europe, they expand into the little island of the step that's in the Great Ungarian Plane and the Carpathian Basin, and they stop, they can't expand their way of life to the forested parts of Europe, which is most of Europe, and somehow the ancestry of the Yamnaya gets absorbed by the courted -were group, and then later the beaker group, and that takes it further through Europe. But the courted -were group is quite different from the Yamnaya culturally, and in fact a lot of archaeologists think that they're so different, they can't be the same.

1:10:16They share some shared features, but the courted -were have many different traditions. One possibility is that the Yamnaya expand, and they encountered early courted -were, the courted -were learn some of the adaptations of the Yamnaya, and then they actually take Yamnaya women, absorb them into courted -were mostly male communities, and create a new community in that group expands. So one of the mysteries of the Yamnaya expansion was everybody had this cognitive bias to think this is very male -driven, people of these Indo -European notions of sort of male -centered mythologies and so on. And so this must be an extremely male -centered migration, and the very male -centered migration.

1:10:54You look at the genetic data, and you look at the Y chromosomes, which track male migration, and the mitochondrial sequences, which are more sensitive to female migration, and it looks like the step expansion from the East to West is very both sexes, both males and females expand, and people have found this confusing, and there's been a lot of incredulity about this, people expect to see that it's an even movement of males and females, but it's quite clear that the bias is not so strong. And we think the most likely explanation for what's happening now is that it actually is a male -biased process, but it's one that's interrupted.

1:11:29So the Yamnaya expansion is very male -biased. It expands the edge of the range. They encounter the courted -were complex people. And then what happens is the courted -were complex people interact with the Yamnaya people, and in fact, the Yamnaya people actually are lose out in that interaction, and in fact, the courted -were males absorb and take Yamnaya females, and they actually also take farmer females, because you actually see these sites and early courted -were sites and check you where both things are happening, females from farmers and females from Yamnaya are being absorbed into the courted -were community, and then they expand further.

1:12:10So what you actually have is a two -step process, where you have a male -Yamnaya expansion, and then that ancestry from the step is carried further through females being absorbed from into the courted -were, and then another male driven expansion under the courted -were, and so on. And that brings both female and male -Yamnaya lineages west, but not always with the Yamnaya ancestry being associated with the kind of intuition that you would think it's domination. The same sort of parallel thing in another part of the world is what you see in Ramotoshiania in the southwest Pacific. So if you look at Vanuatu, which is the islands, some of the first islands that people got about 3 ,000 years ago in the southwest Pacific, so moving to the southern part of the world, if you look at New Guinea and Australia, people are there almost a little bit after 50 ,000 years ago.

1:13:03People are in the Solomon Islands and the Bismarck archipelago to the east of New Guinea, maybe 35 to 40 ,000 years ago, and they stop in the Pacific as all these fertile places that are good places for people to live. It's completely empty of people until 3 ,000 years ago. Suddenly, these people from Taiwan go through the Philippines, they skirt the edge of New Guinea and the Bismarck archipelago, and they get to Vanuatu and Fiji and Tonga and New Caledonia and Samoa, about 3 ,000 years ago, super rapidly in the guise of something called the Lapida Cultural Complex. And if you look at the DNA of the people from this, they're almost entirely East Asian and ancestry.

1:13:39They look like early Taiwanese people. And today, people in Vanuatu and Fiji and Tonga and New Caledonia have only 10 % of this DNA. So something else happened afterward. The first people are almost entirely East Asian, via Taiwan and the Philippines. And then you look at later DNA from the same part, and 2 ,500 years ago, 500 years after the initial arrival, there's mass movement in a male -driven way from New Guinea and the Bismarck archipelago into Vanuatu of Papuen. And it's people with overwhelmingly Papuen ancestry from New Guinea coming into Vanuatu, and that's the origin of the ancestry that's overwhelmingly there in Vanuatu, New Caledonia today.

1:14:19So there's two -step process. The initial step, which is East Asian ancestry and these people who invented Outriger Canucic technology and long -distance sailing. And then the technology becomes adopted by Papuen's who are using this culture for the next few hundred years. We can see them trading back and forth between the Bismarck archipelago in Vanuatu. And by the end, this culture is carried out by Papuen ancestry and males from this group then spread into Caledonia and take local females. But the ancestry is flipped from the way that people have this cognitive bias that should be. So people think, oh, it should be the East Asian males kind of somehow dominating the local females or something.

1:15:00You see the reverse, and this is what's going on. And it's not like it's very complicated in subtle. So when you actually see evidence of males and females behaving differently, it proves that there's socially asymmetric behavior of two groups as they interact with. What it means is confusing. It could be female mate choice. It could be violence. It could be genocide. It could be different patterns of male and female dispersal with groups who travel being of one sex or the other. And we can look for clues in the genetic data. And certainly in concert with the archaeology, we can maybe figure out more.

1:15:40That's really interesting. I guess I was speaking of this, going to a totally different era, but something I'm curious about. So going back to our case, humans. And we talked a lot about Neanderthal's, but obviously there were two different species of denisovans, right, I don't know the species is the right word, but two different kinds of denisovans. And also, I think the Hobbits in Asia, right? And then I don't know there's more, but we were talking about half a dozen different distinct groups and only one survives. Do we? I understand it's like a new cultural technology is developed by this near -east early tribe that then they expand out through Eurasia.

1:16:22And I get that might enable them to be so dominant. What I don't understand is, how is it that none of the other one survived? Like not even one tribe of denisovans, or like one group of Neanderthals, one group of Hobbits, there's no niche in which they could just like fend off. Everywhere this one tribe of humans, one tribe of African humans just dominated. I don't know if I asked a question in a, like how did none of them survive? Yeah, I don't know. I mean, I think it may be a numerical issue. I mean, if you look at the part of the world where we have the best data in the Holocene, the last 10 ,000 years, there are places of long -term survival of hunter -gatherers for a few thousand more years than elsewhere.

1:17:06In the Netherlands, for example, hunter -gatherers survive for several thousand more years than in the surrounding areas, probably because they're exploiting the wetlands. But they're gone soon enough. Once something happens, mammoths go extinct mostly 14 ,000 years ago, but they survive on Rangol Island, North of Serbia, until 4 ,000 years ago. So at some point, each of these places is encountered by the spread of modern humans at high densities. The other thing is it's not even clear to me what expansion means. So if you want to make a strong argument, you might argue that non -Africans today are Neanderthals, who just have waves and waves of modern humans from Africa, mixing with them.

1:17:44Who are the ancestors? So that might sound like a silly kind of philosophical statement, but like, genealogically, I don't know if this happened before or after my book. You probably don't know about this, but there was a super interesting series of papers that came out which made it clear, many things became clear. But one of them was that actually the proportion of non -Africans ancestors who are Neanderthals is not 2%, which is the proportion of their DNA in our genomes today if you're a non -African person. It's more like 10 or 20 % of your ancestors are Neanderthals. And what actually happened was with when Neanderthals and modern humans met and mixed, the Neanderthal DNA was not as biologically fit.

1:18:26And the reason was that Neanderthals had lived in small populations for about half a million years since separating from modern humans which had lived in larger populations and had accumulated a large number, thousands of slightly bad mutations such that in the mixed populations, there was a selection to remove the Neanderthal ancestry. And that would have happened very, very rapidly after the mixture process. And there's now overwhelming evidence that that must have happened. And so if you actually look at the ancestors, if you count of your ancestors, if you're of non -African descent, how many of them were Neanderthals say 70 ,000 years ago, it's not gonna be 2%, it's gonna be 10 or 20%, which is a lot.

1:19:06And maybe the right way to think about this is that you have a population in the Near East, for example, that is just encountering waves and waves of modern humans mixing. There's so many of them that over time, it stays Neanderthal, stays local, but it just becomes over time, more and more modern human and eventually it gets taken over from the inside by modern human ancestry. This is what happens to Northern European hunter -gatherers, they become farmer over time, but they're intact on the male line and culturally they stay on the male line intact. And so I'm not trying to be politically correct.

1:19:41I'm just saying that you can actually have scenarios where this happens. So for example, in elephants, if you look in forest elephants, which are the smaller of the two species of elephants in Africa, some of that they're very matrilocal, they pass, they have these female lines that are very intact over a long period of time. And if you look at these, sorry, Savannah elephants, which are the bigger elephants in Eastern and Southern Africa, they have Savannah elephant DNA overall, but their mitochondrial sequences are forest elephant, which are the smaller West African elephants. And the interpretation of this is that you just have waves of waves of dominant male bulls from the Savannah coming into populations and eventually just replacing all of the genome in waves and waves of waves of an intact forest population.

1:20:21And so all that's left is the mitochondrial sequence, which is passed on the maternal line. This is not even obvious that non -Africans today are modern humans, they're just maybe their neanderthals who became modernized by waves and waves of Admixture. One question you could have, because we were talking earlier about how small the initial population that populated all of Eurasia was, that was like a couple thousand people. And one question you can have is like, if, and we were also talking about how random and contingent the whole history of humanity has been, and one question you could have is like, was there some chance if a couple of variables were different that modern, like quote unquote civilization, basically greater population density, greater development technology, so forth, would not have happened except for some really, really lucky chances, or it wasn't the case that even if that one tribe didn't do it, some other tribe of humans would have done it, and even if some other tribe of humans of Africa hadn't done it, then like neanderthals had enough cognitive sophistication that they would have done it.

1:21:24I know this is a very sort of like speculative question, but just like how random does primate to civilization field, does it feel like we had to go down the exact right path, or was it like this is kind of the trend across many different branches of the family that leads to humans? I don't know, I mean, it is very speculative, but like I'm very tempted to think that there's so many of these groups that some of them would eventually have gone down this route, and one example of this that's interesting to think about is the parallel development of agriculture in the Holocene, different parts of the world.

1:21:59So you have in the Americas what's almost certainly a completely independent development of agriculture, 9 ,000, 8 ,000 years ago, from that in Eurasia, you can argue whether the East Asian and Near Eastern developments are different, they probably are, but maybe you could argue they knew about each other somehow, or the Papuan one, maybe you could argue they somehow knew about what was going on in other parts of the world, but probably didn't, but certainly the Americas one was isolated, and suddenly for the first time you have these independent evolutions of full blown agriculture at the same time in many places in the world after the Ice Age.

1:22:31This makes you think that it's somehow deterministic, that somehow some kind of set up of characteristics at this time causes this to happen, and why doesn't it happen at the previous period of stable climate before the last Ice Age, some people say, well, maybe it was actually not as good as the last 10 ,000 years, but I find that confusing as a statement, it seems that somehow some set of characteristics, it's tempting to think that some sort of cultural or biological, but more likely cultural characteristics are in place and seated already at the time of the last Ice Age, such as when the reemergence happens, this happens in multiple places simultaneously.

1:23:15Because it happens so fast, right? It's not like you had to wait for 10 ,000 of the years after the Ice Age, it's literally 2 ,000 years after the Ice Age. That culture's very old in the Americas. Okay, so then the Ice Age, was it 100 ,000, or how old is it? Before that, like human split off 200, or at least some branches of the human tree split up 200 ,000 years ago, and the end of the Ice Age split off even before that, but that's like before the last Ice Age started, right? So to the extent that your earlier statement about like a lot of cognitive subsuscation was already evident 200 ,000 years ago, or 300 ,000 years ago, doesn't that imply that before the Ice Age, we should have seen agriculture?

1:23:53Yeah, it's tempting to think that. So I'm very confused about this personally. People say that the last 10 ,000 years are very unique on a scale of millions of years. If that's true, maybe we're in a very special time, that is somehow a period of warmth and stability of climate that's unprecedented for 2 million years. Maybe that's true, but the other way people often say is that we're in these cyclical periods of a few tens of thousands of years, and the holocene, the last 12 ,000 years or so, is a period of warm warming, and then there's a period of a couple of tens of thousands of years, which is the last Ice Age, and then there's prefer that.

1:24:26There's a few tens of thousands of years of warming, and that's when we sample the Neanderthals, the late Neanderthals from, and then before that, there's another stage of cooling, and then before that, another stage of warming. So this is marine isostype type, stage one, three, five, seven, nine, are the warm periods, we're in one now, and marine stage two, four, six, eight, and so on, are the Ice Age, so the last glacial maximum was marine isostype stage two. If there were quote unquote lost civilizations, maybe not obviously not as sophisticated as anywhere close to the last thousands of years, but maybe early summa or something like that, or like, Comanche, Slash, Yam Nile level, or something, but that happened before the Ice Age, or maybe in a part of the world, during the Ice Age, where climactic conditions were better, would we be able to tell based on motor techniques?

1:25:20I think we would. Okay, and there's just not any evidence of them. I think nobody has found, I mean, there's very sophisticated human burials in Europe, in Africa, in East Asia, in different parts of South Asia, and Eurasia, and so on, Australia, in the last, you know, in the marine isostype stage three, in the last period of warming, and, you know, burials full of beads, burials full of symbolic behavior, maybe you interpret this as civilization, but extensive settled societies you don't see. I think we touched on this when we're talking about population size, but like, one thing I'm sort of confused about when we talk about, the lineage is like, in one sense, a lineage is very distributed, because obviously many different archaic humans contributed to the human gene line.

1:26:09In another sense, it's also like, maybe the main one is a couple thousand people, so like, I don't know if there's a question there, but like, I'm not even sure how to think about the, can they just like hang out in like the size of Montana, like the entire human lineage is? I think that the sort of lesson from ancient DNA and the genome revolution has been that, any one in the world is the result of recurrent mixture, again and again in the past. So you might think that the last 500 years are unusual periods of history with the people of African and European and Native American ancestry coming together in the Americas, and that this is unusual because of transatlantic travel, but almost every group in the world is the result of many mixture events as profound as these on many timescades.

1:26:55So South Asians are the result of mixture between groups very different from each other as different as Europeans in East Asians, four to three to two thousand years ago, coming together and then crystallizing into a relative lack of mixture. Since that time, Europeans are the result of mixture of Yamnaya and farmers and hunter -gatherers, people in different Near Eastern groups are the mixture of kind of early Iranians and early 11 -team people and Anatolians who are super different from each other. There's huge differences amongst East Asians, huge differences amongst Papuins, any Asians, profound differences with Bunk's different Native American groups that come together to form groups that we have data from later, an example after example we look for.

1:27:34So if you think about any one lineage today, any one group of people and you want to trace people's ancestors back in time and think where do our ancestors scatter in geography at different time points, almost everybody's ancestors are scattered into different geographic distributions that are not all in the same place. So the evidence that our lineage was mostly in Africa is based on an idea, I think assumption, a kind of inertial idea that our lineage has must have always been in Africa because Africa is the central central human history. But if you look at the archaeological evidence, it's not incredibly clear.

1:28:11And if you look at the genetic evidence, we have many early branches from Eurasia and only one from Africa and complexity and branching in Eurasia that's sampled in the DNA record, DNA from Denisovans, DNA from unknown archaic lineages that contributed to Denisovans, Neanderthals, and all of those are represented in the Eurasian record, not in the African record. Part of that is the fact that ancient DNA is preserved in Eurasia. But maybe actually what there's a period when our lineage resides in Eurasia, it's not obviously wrong. So I think that hypothesis is out there as a possibility. When I think I would love to see, I don't know if I assume this will change over time as more difficult comes up, but some sort of like chart that is superimposed upon a world map, and it evolves over time.

1:28:58And then maybe you can just have sort of blogs representing different population groups. You can start up with the archaeic humans and go back like 200 ,000 years ago. Go back even before that because if this is a global event, it's not just an African event. So for hundreds of thousands of years, you can just see different populations splitting off, merging back together. And if you can make somebody make that sort of animation, I think that would be a very useful. I think you can. People have tried to make animations like this in some way, but one way to think about it, I think there's a huge danger in being too interested in yourself.

1:29:30This comes across in my book, I think. But it's very, very tempting to be interested in your own history and think it's important. It's obviously not important compared to other people's history. However, if you think about one person's history and you think about where their ancestors lived, two generations, four generations, eight generations back in the past, those are your great grandparents and great, great grandparents. You may even know where they lived. But then you can actually plot on a map at different number of generations back in the past where your ancestors lived. And it's interesting to do within your family because maybe you're from, ancestors going back a few generations are in Europe somewhere, different parts of Europe, for example.

1:30:08People do this and when you get a test back from one of these personal ancestry testing companies like 23andMe, they'll say, oh, you are 20 % Irish and 30 % Chinese or whatever it is, and so on and so forth. And what they're referring to is rollback 20 or 30 generations, where are your ancestors scattered in proportions? But then if you rollback 3000 generations, there's some in East Africa and some in the Andrathals. So what you can actually do is for any one group of people or any one person, there's different time slices that matter. 30 generations ago, you get the 23andMe output. 3000 generations ago, you get the proportion of your ancestors who are Neanderthals or not Neanderthals or Denise Evans or something like that, if you're from one of the many populations around the world that live in Denise Evans.

1:30:53If you are any population going back further in time, presumably there's something similar happening where mostly in Africa but possibly outside of Africa 300 ,000 years ago, people's ancestors will be coming from different places. It's very plausible that people's ancestors are not all in Ethiopia at 200 ,000 years ago, that in fact some of them are in North Africa, some of them are maybe in West Africa, some of them are in South Africa, some of them are in Eurasia, and that actually appreciable fractions are in each place, and that braid and that trellis is coming together again and again over time, as you move further back, they'll collapse, some will go extinct, some will reappear, some will re -merge, and at any one point, there's never a single similarity.

1:31:32I don't know if you're familiar with Nat Freedman's Vesuvius Challenge. I don't know if you saw that one or was going around. So the scrolls in the library at Herculaneum, there's a volcano, I forgot, it was like, was it basically during the Roman Empire? Sorry, 980. Okay, well, yeah. The end, it buried the scrolls in that library, they all became literal ash, or at least very burnt. So Nat Freedman found this professor who had done CT scans of these scrolls, but there was like no way to decipher them, we just had the CT scans. But it felt like this is the kind of thing where somebody out there might be able to figure out a technique for how to do it.

1:32:16We know what the end results should look like, we just don't know what the intermediate steps look like, but it feels plausible with modern technology. And so you offer a million dollar prize and a 22 -year -old or 21 -year -old with a GPU and some coded up a, I think a CNN model to decipher these scrolls. And anyways, is there something in your field which has this sort of feeling where there's something we need to figure out. We don't know the exact right technique, but if you could put it out and just offer a million dollar bounty for it, maybe somebody will come with a cool new technique to figure it out.

1:32:52Yeah, I don't even, there's like many things in this area, but I'll give you, I'll give you a simple one and then I'll give you, I probably should give you a single answer. But I think that the basic answer is what we need is DNA from Africa. So we need DNA, old DNA from 50 ,000 years ago, 100 ,000 years ago, 200 ,000 years ago, from all over Africa, because it's super clear that our lineage is complicated with in Africa. There's archaic forms and the archaeological record and modern human data is extremely substructured with evidence of having come together for many different lineages, which must have been different archaic forms in Africa and contributing to people living today.

1:33:34So having that would crack our understanding of how modern human lineages break it together and relate to the other archaic lineages we have data from. So that's obviously extremely important. What is it you need to get the samples? I think we need to identify those skeletal remains or the sediments in old caves that are well preserved, that had rock shelters that contain enough DNA to extract. And I think we need extraction techniques that will allow us to get at that material. Maybe we even already have them and we just need to wait until that begins to happen. But it would be revolutionary because the experience in Eurasia has been when we get DNA from old sites or new sites for which there's been nothing we find in East.

1:34:14So we find people like we completely didn't expect to see before that break our understanding of the past. I think the other area where I am super excited and I think it would be a thing to reward and to incentivize would be to try to crack this body of information to try to understand how biological adaptation happened in the last hundreds of thousands of years. We simply don't know the answer to your question from a genetic point of view about how modern human cognitive and other types of propensities, how they develop the biological underpinning of the differences that modern humans have from our closest living and relatives.

1:35:02We just don't know how they evolved. It's not even clear how biological they were. But being able to interpret the genome in terms of how these changes occurred is we just don't know how. I was at a talk a few years ago that was really shocking to me, which was based on there was a researcher at Caltech and she was talking about being able to directly read the brains of Macac monkeys. Monkey would be shown 2000 photographs and she would and her student would be recording from different neurons in its visual cortex and learning the neurons response to different images. And so what they would do is they would decompose the images of faces, human faces, into eigenvectors with the principal component analysis.

1:35:47And then the neurons, specific neurons were responding to particular eigenvectors and they learned the language of how the photographs and the decomposition of them computationally mapped on to the neurons and they actually learned a language for how that's the case. And then what they did is they showed a 2000 and first photograph to the monkey. They recorded from its neurons and then tried to use the neurons to reassemble a photograph. And it was a perfect reassembly of the photograph. They had actually completely learned how the brain, this calc's brain represents the photograph going through the brain representation.

1:36:23So in that case they were able to completely figure out the language of appreciation of a photograph through the biological representation of it. And if you look at the parallel problem of the genome, how does the genome code for development and how we are get to how we are today, how do we have our capacities and so on. To me, it sounds like at first principles, if you ask me what's a simpler problem figuring out how to represent the natural world in our brain or figuring out how to code for development, I think I might cognitive bias if you were presented at the NICIO, this problem would be to say it's easier to code for development than to represent the outside world in a brain.

1:37:01But this group and other groups are figuring out how to do this nearly perfectly with a readout from the brain. And we really can't read a genome and tell you how a person looks, how a person develops. You know, we can begin to say what terrible diseases they have, but not even predict that so well. And so that's very depressing that we can't actually read the genome enough to actually see how that occurs. And we actually don't even know how evolution happens. Like for example, does evolution happen by lots of little changes pushing in some direction, like for example, if we want to move toward a different positive set point for height or for some cognitive capacity or propensity or something, you know, is this by infinitesimal change of polygenicity, many genetic variants pushing in the same direction?

1:37:43That's the mathematician's bias. Or is it like the example I told you about before with David Galkman and Lyron Carmel with the voice box where everything pushes in the same direction and goes up to 100 % and she's all in the same direction in an incredibly simple and simplistic way. If you talk to neuroscientists and molecular biologists, their brain tends toward the latter. And this few examples suggest that maybe that's occurred. And so maybe this kind of polygenic paradigm of adaptation when adaptation really matters, is that really what happens when important adaptation happens? Happens? Or is it instead something simple and simplistic and reliant on a small number of genes?

1:38:21So what I would really like to know is can we mind the genetic data we have from modern genomes and archaic genomes? We now have Neanderthals and Denise events. We now have some early modern humans who are far enough back in time that appreciable change may have occurred. And can we actually learn the patterns of at biological adaptation well enough to actually read the code of how we change and how we adapt to new pressures? And I think that that's something that's not impossible to imagine. We can learn how to do. But it takes a different way of thinking. One thing that it'll also be interesting there is one big debate in trying to forecast AI is how big is the information content that describes the human brain?

1:39:00Because with AI models, we know obviously we can tell very easily. Here's how difficult it is to... Here's how many bits it takes to encode the parameters. But if you want to go back to how many bits is it to encode the training paradigm itself, there's obviously this training code, then there's a hyper parameters, and here's how many kilobytes that is. And the question is, we know that the human genome is through gigabytes. But we know only a small fraction is protein coding, and then also how do you count the percentage that is responsible for regulation and so forth. But if you could only get the part that is responsible for the brain, how big would that be?

1:39:40Can we compare how big that is with respect to how big the training code for a model is? And then we'll give interesting insights into how similar those two processes are. So what we're beginning to be able to do, I mean, I don't know how important the particular class of work I'm involved in right now, but we're engaging with this in some way right now, because we have incredible data from Europe in the last 10 ,000 years with huge numbers of samples, where we can watch very small changes and frequency over 10 ,000 years. So in this period of time, which is not a particularly important time in human evolution, it's well after the important stuff happened.

1:40:16It's the last 10 ,000 years, but it's an eventful time. The environments became very different. The lifestyles became very different. And so this is a period of time where we've done an experiment of nature. You can push this happen against the human genome. There's agriculture, there's people living more densely, there's infectious disease happening in a different way, in a different type than before. And how does the genome respond to this traumatic set of conditions? And so you can actually watch all these little variables, all these little gene frequencies, tens of millions of them shifting up and down in coordination.

1:40:46And what can you learn from that? Because we now have all the measurements, right? We have a selection coefficient measure that 10 million positions across the genome. How do you? And we know that what the effect of those on traits today, because they've been measured in large numbers of them on the order of a million people today. So what can you do with this data set? How relevant is this to important evolution? So I think that that's the type of rich data that could potentially be mined to learn something sort of qualitatively interesting. Beyond the storytelling that's characterized molecular biology, beyond the Fox P2, where you say, oh, maybe it's this is maybe this is the holy grail or maybe that maybe that's the holy grail maybe maybe you learn something about the process.

1:41:26That's that's that's that's that's that's deep and profound. And so I think that nine million dollars goes to someone who can actually come up with a way of thinking about the process. That's really kind of qualitatively profound. Interesting. All right. Well, you heard I guess we need to find the million dollars first, but somebody if you've got a million dollars and somebody else if we got the idea, well, we can make a mark in here. One of the interesting things we were talking about the contingency of human history and human evolution. And one of the really interesting things is not only is a contingent, but it seems to be persistent at least across the last 2000 years and the way that genetics have changed, culture has changed.

1:42:02So the when the Indo -Europeans, the Amnaia, disrupt, you know, whatever the industrialization for thousand years ago or something like that, the the not only does that mean that the languages which are spoken in yet today or at least many of them are descended from this group, but literally the actual like core myths of Hinduism are descended from this initial group. How is it possible that for four thousand years, the things like caste, things like basic mythology can be preserved with such high fidelity, especially in an era for half of that you don't have writing, not half of that, for at least a couple thousand or two thousand years, you don't even have writing.

1:42:46How is that sort of persistent cultural irritability preserved? Well, you're asking me a cultural question, not a genetic one. So what you see in the genetic data from South Asia is an amazing process. So today in South Asia, almost everybody is on a gradient of ancestry with two poles, what we call the ancestral North Indians and the ancestral South Indians, with very few exceptions. The exceptions are people with your last name, Patel. Oh yeah. And as a minor exception, but it's interesting that that's your last name, but also people from Munda, like Sue speak Austrian, theatic languages or amixed with them or people who are Tibetan -Berman speakers, but most people are on a mixture between two poles, ancestral North Indians and ancestral South Indians.

1:43:34And when you look at genetic data from India, it looks like what you see today in African -Americans with people with relatively higher or lower proportions of, say, European and West African ancestry. And so it looks like a population in the process of mixture like African -Americans who are the result of mixture in the last 10 or so generations between two, mostly two very different populations, mixing and different proportions. So, but what happened in India is it froze. So the mixing started and then it froze. And the freezing happened two to 3 ,000 years ago and it froze because of cultural change.

1:44:11So what happens in India is you have a three -part change. You have a arrival of three -source populations, essentially parallel to what you see in Europe. There's a local hunter -gather population. There's what's probably a farming population, maybe also hunter -gather population initially. And then there are these people descended at some level from step -pastoralists. These are the three primary ancestral populations. They come together at the end of the decline of the Harappan civilization, which ends about 3 ,800 years ago. And groups from this Harappan group, which we actually have sampled and they're all on a different gradient, they mix with the step groups and with the local hunter -gather groups to form and coalesce to these two later groups, which we call the ancestral north Indians and ancestral south Indians.

1:44:54And then mixtures of these two mixed populations form in the gengetic plain, form people all along this gradient. And it's really a very simple mixture of two sources. And then the cultural change happens, which locks in the caste system and people freeze and they stop mixing very much. And so what you see is instead of people collapsing to a point, which is what you see in Europe after this type of mixing process of these three sources happen in any one region, you see this gradient forming and it's stable. And because of the enduringness of the caste system, you actually have a snapshot going back a couple of thousand years and without this continuing change.

1:45:32And so it's kind of an amazing system genetically to look at because of people's reluctance to mix with people from very different groups in traditional communities. And so the three steps are coming together of very different populations and then convulsive profound mixing of groups that had previously not mixed and then locking into this static system as the caste system sets in, which is documented in the early texts like the Rigveda. And you can actually see the change in that discussion during the course of the Rigveda. I know you weren't about being too interested in yourself, but what was it about the Patel's Warrantain Exception?

1:46:12So the first good genomic data from South Asians is embarrassingly from Houston, Texas. So in the Human Hapletite Matt project, there was a sample from Houston, Texas of Gujarati's and Houston, Houston, Texas. A lot of a lot of a tells in Texas. G -I -H. And if you look at them, people are actually not on this gradient, but they're in a few different places. They're clustered into groups. And there's the main gradient, and there's an off gradient group. And I forgot how we figure this out, but someone figured out that these people are all Patels. And Patels have their own distinctive history with different relationships to people in Central Asia.

1:46:45And it's probably some additional ancestry from Central Asia, pushing them off the main gradient. Interesting. We've obviously talked about so many different different types of fields. I'm not sure where exactly in what field you started to research, but obviously now your lab is doing stuff in genetics. And you have to touch on how does your research combine with archeological record? What are the inferences you can make from that? Or obviously with different kinds of history, there's so many different disciplines here. And how does one sort of like, you start your field that is researching a certain topic?

1:47:24Do you just keep expanding? Now I'm going to master archeology. Now I'm going to master and anthropology. Now I'm going to, like, how does that process work through your career? It's very unstable life. So I think that in some areas, like in archeology, a lot of my colleagues who I respect tremendously, the career trajectory is you learn to become an archeologist, you dig, and you have a set of digs that you're doing for dozens and dozens of years with similar or slowly evolving techniques. And my work has just changed so radically. When I started doing this work, one could not sequence a whole genome.

1:48:00The genome was not yet sequenced. We had very little genetic variation accessible. The amount of data has increased by orders and orders of magnitude every few years. The types of data that we collect, the ability to collect ancient DNA beginning 14 years ago, the ability to generate the volumes of it we have. We had no DNA ancient DNA in 2009. And then in 2014, we only had a few hundred individuals with genome scale data. We have tens of thousands of individuals with genome scale data. We had data from places we didn't have data before. So it's such a destabilizing process. And so someone like me wanders into areas that I'm not expert in.

1:48:39I'm not South Asia. And I get to be part of trying to learn about the new history, about history of South Asia. I get to interact with archeologists at the cutting edge of learning about ancient Southwest Pacific or ancient China or ancient Southern Europe. It's like an incredible privilege, but also I'm a kind of reg amateur in terms of a lot of the work I do. So one wanders from one area, one's an amateur into another area, one's an amateur in and tries to learn a lot. Maybe this is a little bit like what it's like in Silicon Valley right now, with constantly doing new things and bringing some skills to bear that are useful and hopefully trying to be respectful of the people one works with and the knowledge, the tremendous knowledge people have and to learn as much as one can and to work with other people to try to produce some joint research product that makes progress.

1:49:36How do people say like I don't know, somebody's doing archeology for the entire career on a certain group and some mountain somewhere and then you come in and you have like, you know, here's a paper we figured out what the exact right the exact genetic combination that explains all your research is, is it like, is there reaction usually?

1:50:01I don't know how much of this you can save it. Like basically are people sometimes disappointed that you've been able to figure out the things in their field with a different technique or I think that a lot of people we work with are incredibly excited about being able to do this. Prehistory is a period of time we know so little about. We have such poor clues, true archaeologists who are truly dedicated to understanding the past are super thirsty for knowledge about the time periods and if a new scientific technique becomes available that can probe these times, the true archaeologist who are truly interested in the past get incredibly excited and they embrace it as they've embraced previous scientific techniques such as scientific archaeology such as isotopic analysis such as radiocarbon dating and that's been my experience with people again and again in archaeology with people who really want to know about the time periods before writing when at some point one didn't even imagine one could learn anything.

1:50:54Being excited about this new type of information. I think sometimes people are dug in to particular views of the past that are challenged by the new findings that come from scientific research such as ancient DNA and when the DNA is strictly in opposition to some of these models that becomes an area of tension and I think I have found myself to be proven wrong in a number of cases including by my own work or by other work amongst my colleagues and like I hope to be someone who can welcome that. One of my idols in this field is the archaeologist Colin Renfrew who is a British archaeologist who is responsible for the Anatolian theory of Indo -European origins.

1:51:44The idea that farmers spread Indo -European languages, the language spoken in Armenia and in Iran and in northern India and in much of Europe today spread with farming after 8500 years ago from Anatolia in all different directions and that the demographic expansion and economic transformation associated with that spread farming. It's very plausible and there was a debate with Maria Gimbuthas and others who argued that these languages spread from the step north of the black and caspian species and one of the main arguments for the Anatolian hypothesis was that step expansions could not have been demographically significant because they were much thinner on the ground than farming expansions and that this is why the step could not explain it even though other linguistic arguments made the step seem more plausible.

1:52:28And so when the genetic revolution happened with regarding to our understanding of Yomni expansions and Indo -European origins in 2015 Colin Renfrew at some point said I was wrong. I was wrong about this topic. In fact, it's the weight of evidence now suggests that in fact demographic transformation did come from the step. It's kind of amazing. It's did. Maybe it's from disease. Maybe it's from something else. Who knows what it is. That's a very interesting topic. But we adapt. We learn. So I think that this is this is incredibly inspiring to be able to change one's opinion. Final question. So you mentioned these different revolutions in our ability to understand the past.

1:53:03The radiocarbon dating to not obviously now with ancient DNA and genomic sequencing. Is there something that feels like the next thing along the spectrum? Because one would hope in the very future. Like a thousand years from now, the future AI is working on looking back on human history. And hopefully there's like no lost period. Hopefully literally they know what kind of gods the tribe and the Near East that basically settled Durejia worship. They would know everything. And then along that spectrum we're making progress. But what is the next thing after advances in more genomic sequencing and more samples from different parts of the world?

1:53:46I think I don't know. So the discovery of the ability to extract DNA from ancient human remains was such a shock that we could even do this. We just didn't think we could do this. There's a lot there's a section in the introduction of my book which was sort of my impression of what it was like. I had a conversation with my PhD supervisor about what it would be like if one somehow could open a cave or a room that was echoing still with languages that don't exist anymore that are not yet spoken. And you could hear the word still echoing somehow after thousands and thousands of years and record that down.

1:54:24That's what ancient DNA is like. It's an unexpected gift from the past that this what we thought was an incredibly delicate biological molecule. In fact, it's intact. And there must be other such things just it's hard to imagine what they are. In ancient DNA there is an extraordinary amount still to do. So there is systematic sampling from many many places in the world where yet there has not yet been sampling. There is systematic sampling and the ability to sample from deep deep into the past up to the point where we can begin to decouple these lineages from each other. I think that will reveal incredible richness.

1:55:04And I think that that's something that we should all look forward to the insights that come from that both in terms of the understanding of individual places including places like many parts of Africa and South Asia and Australia and New Guinea and so on where we have essentially no data currently in terms of ancient DNA. But also in terms of deep deep deep time and the deep lineages that mix together to form us where we really have no sampling except for the Denise events in the end of falls right now. I think that's a great place to close. David, thank you so much for coming out the podcast.

1:55:34I highly highly recommend your book, Who We Are and How We Got Here. I mean, yeah, just so wild. Just basically a lot of the stuff you learned in grade school at least needs a lot more clarification. Some of it is wrong. And the fact that that's the case is crazy. And I hope that I don't know in five to five years, 10 years, there's a new addition of the book or a new future book you write that all the questions that you talked about today, which we don't have the answers to. It seems like there's a bunch of progress happening here and I'm very eager to see what the future of the results look like.

1:56:04Great, yeah.