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David Reich

lines on the record: 144
first: 2026-05-08
most recent: 2026-05-08
sittings or episodes: 1
sources: podcast

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“It's apparently ever been. Yeah, exactly. But it's about strength or courage or religiosity or those are the values, right? Or if you read Homer or the other texts of other religions, it's not intelligence. It's beauty. It's like other things. And so this value system, which has a hyper focus on smarts, is not obviously trait value that's been common in the past. You might think that in certain communities like some communities are not, there might be valuation of things that are more proximate to years of schooling, but really broadly it's not been a high value in the population.”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“I think that that's a great question. And as we talked about before, the human selection is very effective. It can move the mean value of traits within hundreds or thousands of years in one direction or the other if that's adaptive in a particular environment. And so you might wonder, isn't intelligence good in all contexts and places in time. And I think that there's a number of ways to think about that. First of all, I think we are speaking from the point of view of a society which intensely values this particular trait, ability to score well on IQ tests or things like them or to go to school for a long time or whatever it is. And I think this is unprecedented in human history that we live in a time like this. Like if you look at the Hebrew and Christian Bible and you look at how much intelligence is valued, it's basically not at all.”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“Whether they had a relationship, a correlation to the trajectory of those same genetic variants in Europeans over the last 10,000 years. So these are two parts of the world where the populations have been essentially completely disconnected. And there's no way by chance that the trajectory in Europeans over the last 10,000 years will have anything to do with the number of years, the effect on the years of schooling in China today. But there's actually a huge statistical correlation of five or six standard deviation correlation between the effect size of variance a number of years of school in China today and the trajectory in Europe. Just as strong actually as the effect size of variance in Europeans two years of school to the trajectory in Europeans. So we just could not see a way this could happen by chance. And once we saw that we really felt quite convinced that this was a real signal and that really somehow there has been natural selection to”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“Maybe propensity to defer gratification or something, or I make just waving my hands that is under selection and it pushes all these traits in the same direction one way or the other and in different times in the past it's advantageous or disadvantageous. But when we found this signal of years of schooling being increased, the genetic propensity to go to school for more years as it manifests itself in people in white British people today, when we found the signal, we were sort of incredulous, like how could this be? Maybe this is a problem. So we did a few tests to try to figure out whether this was real. And one of the tests we did is we looked for a study where this measurement of the numbers of years of school was done not in Europeans, but was done in Chinese people in China. And we looked at variants that had the effect size of many variants as they affected the number of years of school in China.”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“Yeah, well, I think that there's two things going on that you need to think about. So one of them is that years of schooling is connected to so many other things genetically. So if you look at the genetic predictor of years of schooling, this trait has been measured in millions of people now. It's actually correlated to really, really surprising things. It's correlated to the age at which women have their first kid. It's correlated to people's obesity. It's correlated to people's walking pace. It's correlated to people's household wealth. It's correlated to a variety of other traits that seem quite different from it. So if you think you're actually measuring years of genetic prediction of intelligence or years or actual studiousness or something like that, you should think again because there's many things that it's correlated to. There seems to be some kind of general trait that maybe you could think of as executive function or”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“Genetic predictor of years of schooling, which is highly correlated to it and is measured even better. So, if you look at the genetic predictor of years of schooling, there's another amazing study from 2017 from a group in Iceland that looked at this measure over the last hundred years in Iceland, and it looked at older people, and it looked at younger people, people born more recently in Iceland. And there's an estimated 0.1 standard deviation decrease in genetic predictor of intelligence in Iceland just within one century. It's an absolutely huge effect over a short period. And this is selection against years of schooling, if I said intelligence, I didn't mean to. It's selection against the genetic predictors of numbers of years of school.”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“Right. So, you know, this is the power of data, right? Like, I think Joe, if you asked him prior to this work what the hunter-gatherer selection would be and where their set point for this particular trait would have been, I think he probably would have made a very strong prediction, but he would have said, well, maybe you would have expected it to have a high predicted value of this trait because these people were really having to do a lot of things and figure a lot of stuff out, maybe, and that maybe once you have more complex societies, there would be more of a collective brain and maybe there'll be selection against this trait. And in fact, it's sort of the opposite in some ways. So it's the power of data. It's not what you expect. And after looking at the state, it's actually the value of data to try to make sense of all these things. It's very interesting. The genetic predictor of intelligence, there's lots of kind of things that are confusing about it. So it's actually worth talking about it.”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“So, what you're seeing is those two groups had different set points for those traits. And then the step-past storalists have a lower set value of this. And so you see huge fluctuations in the predictor of this trait over time. That doesn't prove selection. What that is just telling you is migration. But what our test is telling you is in addition to those fluctuations due to migration, is there a consistent effect of natural selection blowing the trait in the same direction over all places and times? And that's what we're detecting”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“One thing you can see in the data is the migration impact is huge. So, for example, if you look at the trajectory for measures of cognitive performance like scores on intelligence test in white British people today, but you look at the predictor of that in people in ancient times, the estimate for the hunter-gatherers of Europe is like three standard deviations below the modern mean. So that's hugely different. And then you see a huge jump from them to the farmers who are like at the mean at zero. And that's migration.”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“In Italy from 2,000 years ago to 1500 years ago, and each of these places where the ancestry is relatively similar without being too disrupted in that short period by migrations, we watch to see if the genetic changes blow in the same direction. And what we're doing here is we're measuring the strength of selection at each point in time after correcting for the big population changes that have occurred.”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“How much the polygenic score trait moves over a 10,000-year period within a population that is held constant in terms of its ancestry. Because what's actually we're doing is we're looking in our data set at a kind of heterogeneous group of people. There's southern Europeans and Northern Europeans and hunter-gatherers and farmers and at different times in the past those groups are more or less represented. So the whole strength of the methodology Aliakbari developed is it corrects for that changing ancestry over time. And as I mentioned before, really what's being asked here is we've divided up our whole data set into an archipelago of little populations in different places and space and time. And we're asking in each place in space and time a little pocket of people in Britain from 4,000 years ago to 3,500 years ago, a little pocket of people in Hungary, a little pocket of people.”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“Past because there was no wealth in the past, there was no school in the past. But if you look at the predictors today, there is a strong movement in a systematic direction, a large effect about”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“In what time are the natural selection strongest and the time period is really two thousand to four thousand years ago? And for some of these other traits as well, you see again the time period over which the selection is strongest is 2004,000 years ago. So for example, if you look at genetic variants that affect measures of cognitive performance, for example, such as performance on intelligence tests in people in white British people today. So this is, of course, a very strange trait to measure in the past because there were no intelligence tests and there was no school. But it is a predictor today and you could look at how it's changed in the past. And we see very strong natural selection for this combination of genetic variants that predicts people's performance in IQ tests and also is highly correlated to the predictor that predicts the number of years of school or the household wealth of people, all crazy traits.”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“And so one possible explanation for that is just that there's only a handful of generations, maybe five, over which the natural selection would operate. And so maybe if the selection was 2% a generation, you would still only see maybe a 10% compounded effect. And there's just not enough time to detect it. But the Bronze Age is not 300 years. It's 3,000 years. It's the power of compound interest. And you have enough time to begin to see a strong effect. But this really, really, really does seem to be a very impactful time in terms of human history. And you can see it in our complex traits. So, for example, if you look at pigmentation, for example, which is the strongest signal of selection for a complex trait in our data set. So you look at genetic mutations that are known to affect pigmentations. You add up their effect across all of the DNA. So there's dozens or hundreds of them. And you look to...”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“That may be the case. It also may be the case that that period is just too short to see much effect. So what you're looking for in the Bati et al. paper where we looked at about 30,000 African Americans and looked to see whether there is instead of the average percentage of maybe around 80% West African ancestry in some places in the DNA more than 80%, in some places in the DNA less than 80% significantly as you would expect if there was natural selection from some genetic variant from Europeans or from Africans, we didn't see any place in the DNA that was significantly different from what you would expect by chance.”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“4,000 years ago. And so it's really interesting, this observation of that being a key point, that being an inflection point, tells us something about when humans, at least in this part of the world, were wrenched into a way of living that was so different from how the hunter-gatherer ancestors lived that the organism had to adapt very strongly. And that maybe the degree of that wrenching process moving into the Bronze Age was qualitatively greater than the degree of the wrenching process that happened from the initial transition to growing plants. Which is surprising because our cartoon picture is that the big transition is farming, but the genetic data, the biological readout, is saying our genome is reacting much more strongly to this events that happened 5,000 years ago.”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“That too has reversed around this period in some of the complex traits that maybe we'll talk about later. These traits too have periods of intensification of natural selection. For example, depigmentation, which is the Europeans have depigmented, gotten lighter skin over the last 10,000 years. You can see it in our data. The period of strongest depigmentation is between about 4,000 to 2,000 years ago. And then after that, it's much less. And so this seems to be a very impactful, eventful, important period where a lot of the processes that we are seeing become very powerful. And it's surprising on first principles. You might think before you walked into this genetic data that the big change is going to be starting to grow plants and maybe farm animals. Beginning, 11 or 12,000 years ago and spreads into Europe after 8,500 years ago. But actually the intensification happens like 5,000 years ago.”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“Multiple sclerosis risk variant inflected and increased in frequency before the Bronze Age and then 2,000 or 3,000 years ago reversed at that period. And there's differences in Northern Europe where this process is super strong, very strong positive selection, very strong negative selection. And then in Southern Europe, only a little bit and not even very strong negative selection. For hemochromatosis, which is iron pathogenic iron buildup that causes problems in Europe.”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“Right. So fads one, two, this variant, it's sort of a vegetarian slash meat-eating adaptation. And already in work prior to this, actually Ian Matheson, who was a former colleague worked with me in 2015, identified this as a very strongly selected variant. And it's actually been ancient. You see copies in archaic humans too. One of the findings of our paper is the ABO blood system. You get your blood typed, it's A, B, and O. The B variant has increased up to 10% at the expense of A. But previous work has shown that A and B were both already present in the ancestor of humans and gibbons, other apes. And so these mutations, some of them have been going back and forth and fluctuating over time in different time periods. But we're talking about changes in the Bronze Age. So this tick-to variant for tuberculosis risk.”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“And if you look at this major risk factor for tuberculosis, this variant rockets up in frequency from eight or six thousand years ago to maybe nine or ten percent in this part of the world, and then it rockets down in frequency in the last 3,000 years. In both cases, there's very clear evidence of natural selection. In the first case, to increase in frequency, and then in the next case to decrease in frequency. And a possible reason for this is maybe the spread of tuberculosis, maybe becomes endemic in the population two or three thousand years ago that's potentially consistent with pathogen sequence data and other lines of evidence. And maybe this variant was protecting against something before then, but then tuberculosis became significant after that point. And it was so bad that it pushed in the opposite direction, that's speculative.”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“Used that way before. So, an example of this is the tick two genetic variant that is a major risk factor for severe tuberculosis, which is the major infectious disease, the most important infectious disease killer in the world today.”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“So we look, one of the things we do in this work is we look carefully at many, many of these positions in the DNA. We actually have an internet browser that you could look at called the Ages browser that Ali and a colleague of his who's a co-author of our paper built that allows you to query each of these 10 million positions and see the trajectories at each position and the evidence for selection. And one of the things that we see is that while for the most part signals of natural selection we detect are consistent with being constant natural selection over time. In a handful of them, we're able to see that there's been a reversal or a radical change in natural selection. And very often that occurs in the period between 5,000 to 2,000 years ago, which is the Bronze Age and the Iron Age, a period of rapid population growth and rapid movement to intensive use of many technologies that were not.”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“Mismatch where you take a genetic variation that's evolved in hunter-gatherers and put it into farmers or pastoralists, and it's not exactly right. And so what you're seeing is the DNA of this population, which is descended from hunter-gatherers only 10,000 years ago, reacting to the shock having been moved into an agricultural and bronze age and high population density in urban environment. And a hypothesis is that what we're seeing is the adaptation that occurs as a result of that.”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“In terms of the way people live in the culture. So, this is a population that almost everybody were analyzing are farmers or food producers in one way or another. Farming was invented for the first time anywhere in the world in the Middle East, 11 or 12,000 years ago. The people who invented farming exploded into Europe after 8,500 years ago and spread across Europe and expanded rapidly in the Bronze Age. There was an intensification of how people lived with much higher populations, people living more and more next to their animals and getting their diseases and exchanging their diseases with them and with each other. And so this is a period of rapid, rapid change in terms of how people are living, resulting in different biological needs of this population. So it's not surprising perhaps that in the context of these dramatic changes, the biology of the population might be not in the ideally adapted position, that is that there might be what some people call an evolutionary”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“So, one of them is that we actually in this part of the world, Europe and the Middle East, are in a period of accelerated natural selection. And one way to see this is to look at this enrichment pattern that we're observing, where immune traits are unusually associated with these selection signals. And we could compare the last 5,000 years of our time period, what's called the Bronze Age and further onward, to the previous 5,000 years. And what we see is that this intensification of selection around immune traits, similarly the intensification around metabolic traits, has accelerated over this time period. So it's not like natural selection has been at the same rate over all places and times. In fact, it's increasing over the time period we're analyzing. And so plausibly, the whole time period has increased compared to previous periods. We're in a period of intensified selection. That's not implausible because this is a population that went through a huge shock.”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“Where we look at our very strong signals of selection, that collection of very strong results is very effectively So, we think there's two reasons why natural selection has, we've been able to prove, really, that there's two reasons why how to reconcile the previous observations with our new observations. Remember the previous observation is that natural selection seems to have been quiescent over a timescale of hundreds of thousands or many tens of thousands of years. Reason that you don't see 100% different in frequency variance across Europeans and East Asians. So now we're seeing hundreds of positions that are rocketing up in frequency with selection rates 1% or more in a lot of cases. So 1% or more selection rates will mean that there'll be a rapid doubling over periods of dozens of generations. And so over 1,500, 2,000 generations, like you see separating Europeans and East Asians, shouldn't you see many genetic variants that are 100% different in frequency across populations? So we were able to show that this is explained by at least two factors.”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“That's exactly right. So it might seem from the results of that analysis that in fact immune traits are highly selected and that there's been no selection for behavior in the last 18,000 years in this part of the world. But in fact, that's a wrong conclusion. And in fact, we have evidence that that's a wrong conclusion. And in fact, there's clear evidence of selection also on behavioral traits. And the reason we think we see and we have evidence that this is so, much weaker signals for behavioral traits is that behavioral traits we know from other studies, medical studies, are underpinned by much larger numbers of genes than immune traits, which are underpinned by relatively small numbers of genes of strong effect. Behavioral traits are shaped genetically by very large number of genes of weak effect, and we just don't have the statistical power to detect these very weak signals there. So when we do it in an”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“Traits, things that might impact your obesity or fat traits or type 2 diabetes, and really almost no detectable enrichment as far as we could tell, for behavioral traits or for psychiatric traits.”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“So we analyze these positions that we had identified, these hundreds of positions, the ones we were super confident about. And we looked to see whether they were randomly distributed in the DNA or whether they had patterns. And what we did is we looked at maybe 100 or so traits where there had been genome-wide association studies for all sorts of different traits, like ones associated with immunity or autoimmunity or behavior or metabolism and basically other things. And for each of these, we could ask, are the genetic variations that are known to affect these traits from genome-wide association studies? Do they have an unusual number of genetic selection signals? And what we found is there was a vast enrichment by about a four or five fold for immune traits. That is, there was a super concentration of selected signals in immune traits, whereas also we saw a strong enrichment for metabolic.”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“No. So if you look at the 25% probability cutoff, there will be tens of thousands. And there will be many real ones there too. In fact, multiple analyses we do suggest that the genome is vibrating with natural selection. And there's all sorts of weaker effects that are there that would be picked up in larger studies even than we've done. And that, in fact, almost every position in the DNA is correlated to a position and being dragged in one way or the other by natural selection. Instead of being quiescent, natural selection is everywhere, even though it's only 2% of the frequency change, it's tugging the positions in one direction or the other everywhere.”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“7200, which we're 50% confident. So I think we're getting about 7200 positions in the DNA that have 50% confidence of being real.”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“Different not because of selection necessarily, but just because they had evolved in different places for thousands and tens of thousands of years. And then if you look at the descendant populations, there's huge changes in frequency. And what you need to do is see, oh, is natural selection explaining a shift more than you would expect by chance?”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“Really, the way we think about the history of Europe and the Middle East and the way we think about it for the purpose of this study is as an archipelago of little populations in space and time, each of which are pretty isolated from each other. So a little population in Britain isolated for a few hundred years, a little population in Hungary isolated for a few hundred years between big events of migration and mixture. And in each of those little experiments of nature, we can ask, does this mutation slightly increase in frequency? Does that same mutation slightly increase in frequency? And if all the arrows point in the same direction, we win, and they're telling us that natural selection is occurring. So, for example, 4,500 years ago in Europe, almost all mutations go through huge frequency changes. And that's not because of natural selection, it's because of the step migration from the steppe north of the Black and Caspian Sea, 40%, 50%, 80% of the DNA becomes yamnaya from steppe pastoralists, and their frequencies of mutations”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“It could count and may count and probably should count in some respects, but it could also be that this population replacement is due to some cultural phenomenon, technology held by one of these groups, not others. And maybe there's some genetic mutations that are contributing to this. Who knows? It's possible. But what you're seeing is a whole genome shift. And so what we're looking to see is whether there's one place in the DNA that is driving the change in a way that's different from the rest of the genome. And really from a statistical point of view, what happens at these times of migration is there's just huge fluctuations in frequencies. And these are extremely uninformative times for looking and detecting natural selection. The best moments to detect natural selection is when migrations and population admixtures are not happening for a few hundred years. And during these times, you can actually see the mutation slowly blowing in one direction as a result.”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“Small amounts of natural selection, or there's been selection to remove bad mutations that are constantly raining down on the genome, but not what we call directional selection, which is newly arising mutations or mutations being pushed in a systematic direction to help the population get to a different adaptive set point. That's more favorable for the conditions that population is living in. So we were able to partition how much of the changes and frequencies of all the mutations that we're seeing in the DNA, we're looking at about 10 million positions that vary.”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“Since 40 or 50,000 years ago is sufficiently small on an evolutionary timescale that there's just not much genetic differentiation on average between these two groups, Europeans and East Asians. But however, if there has been natural selection, for example, to help people in one place digest alcohol better or, for example, digest milk better or do something else better, what you might expect is that there was some mutation that would have rocketed up to very high frequency. And 40 or 50,000 years is a lot of time it's maybe 1500 or 2,000 generations. And so that might be enough time easily to see a hundred percent different in frequency. And yet you don't see any more compared to what you would expect by chance. So this made it seem that just selection has been quiescent, maybe a few hundred thousand years ago, the ancestral human population got to some kind of optimum. And after that, there hasn't been much genetic change in one way or the other. And there's been”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“Has been pretty quiescent over the last several hundred thousands of years of human history. And there's several lines of evidence that have been deployed to document this. One is that if you compare diverse populations from different continents around the world, for example, Europeans and East Asians, and you look at mutations that differ in frequency between these groups, all mutations differ a little bit in frequency sometimes a lot. You can say, what are the most different mutations in terms of frequency between Europeans and East Asians? And there's almost no genetic changes that are 100% different in frequency between Europeans and East Asians. So Europeans and East Asians descend from a common ancestral population 40 or 50,000 years ago that came out of Africa and the Middle East. This population had a set of gene frequencies, genetic frequencies, and these variants bopped around randomly, process known as genetic drift, or perhaps under selection in one direction or another. And the time that's passed,”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“So, seven years ago, Ali Akbari, who is at the time, was a postdoctoral scientist in my laboratory and a few years later became a permanent staff scientist in my laboratory, set out to use the data that we were producing to learn about biological change over time. And I think the reason he was interested in our laboratory rather than other places was that a focus of our laboratory has been generating truly large amounts of data from ancient humans. We've been really trying to industrialize the process, make it very inexpensive, make it high quality, and generate large numbers of samples with lots of good data for this purpose. So there's been this large amount of data that we've generated, and it made it possible to conceive again of asking the question about whether there's been frequency changes over time. So the mainstream view in human evolution in the last several decades has been that natural selection”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“Systematically in some direction in a way that is enough that you can detect it. Now it's very hard to detect slight shifts in frequency by a few percent or a 10% unless you have a very, very big sample size. And so what we're looking for are those changes in frequency that are too extreme to be due to chance, and that will tell us that there have been pushes against the biology as a result of the changes in environment that people have experienced.”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“So, what we're interested in is using the experiment of nature that's occurred in our history over the last tens of thousands of years to understand what's biologically significant in our DNA. And if there has been a change in environment that a population has experienced, for example, people have shifted to agriculture or begun living closer to domesticated animals or moved to a new environment from a cold place to a warm place or a low place to a high place, then there's pressure on the population to adapt to these new stresses, these new needs. And the way you're going to detect that is you're going to see that the frequency of a genetic variant that, for example, might allow you to live at higher altitude, for example, or that might sort of nudge you to have a different behavioral pattern that might be advantageous in the new situation, that genetic variant might push”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“Adulthood or affects a behavioral trait when you want to see how that changes over time, a single person gives you only one sample or maybe two samples, the one that is in their mother and the one that's in their father. And so to get a high resolution picture of how the frequency changes over time, you need to have very big sample sizes of truly very large numbers of people. And we just didn't have that until the last few years. So what motivates this study that we're, I think, talking about today and the work that hopefully another number of groups will be doing in the coming years is the fact that we now finally have those numbers and we can do something with the data to see how frequency changes over time.”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“And one big reason for that has been that the sample sizes have been too small. So when you have a single person's DNA, it provides a tremendous amount of information about history. And that's because when you look at one person's DNA, it's not a single person. It's many people. It's your two parents. It's your four grandparents. It's your eight-great-grandparents and 16 great-great-great-grandparents and so on. And going back in time, thousands, tens of thousands, even hundreds of thousands of ancestors going back in time contributed to people today. So when you look at the DNA of a single person's genome or a Neanderthal genome, you have effectively tens of thousands of ancestors all represented in your data. And you can position that individual exquisitely with respect to other people from whom you have data. But when you are interested in how a particular genetic variant that affects something like your skin pigmentation or affects your ability to digest cow's milk into”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“Well, the dream was that when this field started, this ancient EDNF field started more than 16 or 17 years ago, that we were going to learn a lot about biology, learn about how people's biology changed over time by getting DNA out of ancient human remains and tracking changes over time. And that dream has really not been realized since the beginning of this field. So while the field's been a big success with regard to learning about human history, it's resulted in surprising findings about human migrations, people not being descended from the people who lived in the same place hundreds or thousands or tens of thousands of years before, and mixture being common in human history, sex biased processes being common in human history, and things that were not expected from archaeology. And so the field's been a big success from that perspective. But what's not been successful is learning about biology and biological change.”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source
“A geneticist and I work on human history and how people relate, ancient people relate to each other and people living today.”
2026-05-08 · Dwarkesh Podcast · David Reich – Why the Bronze Age was an inflection point in human evolution · IDENTIFIED FROM THE TRANSCRIPT · source