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Exploring 'A Genetic History of the Americas' with Jennifer Raff: podcast and transcript

Chris Hayes speaks with anthropological geneticist, associate professor and author Jennifer Raff about using genetic data to learn more about the first inhabitants of the Americas.

Who were the first people to migrate to the Americas? When did they arrive, and how? For centuries, those questions have been shrouded in mystery. No written records and very little archaeological evidence exists to provide clarity. In recent years, however, the examination of genetic data has revolutionized researchers’ ability to find answers. A recent family trip to the Grand Canyon furthered Chris’ interest in talking with one of the most celebrated scholars in the field. Dr. Jennifer Raff is an anthropological geneticist and associate professor at the University of Kansas. She’s also author of the New York Times best-selling book, “Origin: A Genetic History of the Americas.” Raff joins to discuss how the first people migrated to the Americas nearly 20,000 years ago, how genomes showcase the very close relatedness of humans across the globe and the impact of genetic discoveries on narratives.

Note: This is a rough transcript — please excuse any typos.

Jennifer Raff: The human genome actually is an archive of our population histories. All of our ancestors who have contributed to our genomes, you can look at their histories just basically by sequencing DNA or genotyping DNA, looking at specific variants across the genome. And using population genetics then to work with that DNA and compare it to other populations and other individuals and say, “Okay, I can see which or I can recreate the point at which these lineages last shared a common ancestor.” And you can kind of do that going farther and farther back into the past.

Chris Hayes: Hello and welcome to "Why Is This Happening?" with me your host, Chris Hayes.

So a few weeks ago, my family and I were vacationing in Arizona. We went to the Grand Canyon, then we went to Sedona, which is sort of the Red Rock region, which is completely amazing. And one of the most incredible parts of the Sedona trip was going on a number of hikes, one of which culminated in kind of going up into these rocks and finding this cliff dwelling that had been inhabited by Indigenous people that lived in that part of Arizona. The Spanish called them the Sinagua, which just means without water. Obviously, that wasn't the name they had for themselves.

They left the region around 1425, we think, because basically of a drought. They were sort of chased out. But their descendants are, we believe, the Hopi and Navajo people who, of course, are still in Arizona today. The Navajo reservation is one of the largest, if not the largest in the entire nation. And I got to say that being out there and seeing, we went to two different cliff dwelling rooms, it really blew my mind.

I guess I sort of feel like when I look at places that get a lot of water, have fairly temperate temperatures, I think to myself, “Okay, like, I can start to conceive of how one would scratch out a living, if you had to make a living without all of the conveniences of modern industrial capitalism. Like, you could grow some corn. You'd have to make a structure. You'd have to burn some heat from wood.

But being in a place that gets 10 inches of rain a year, and thinking about people that sustained society and civilization for thousands of years under those conditions, without, like, obviously, I mean, the things that we have in modern capitalism, it's really mind-blowing. Like, finding enough food to eat in the desert, getting enough water in the desert, creating the conditions for like dense population clusters that do all the kinds of things that human societies do. They trade with each other. They create culture. They do everything.

Like, it's a really incredible and it sent me down this sort of spiral reading about like Hopi desert farming, which is incredible, and still practiced to this day. In fact, it's studied by various agricultural scientists because of how innovative it was, sustained life for 2,000 years in these places. And all that got me thinking about just like how incredible enriched the tapestry of life of this continent was before Europeans arrived here. That's obviously not a novel observation. But it is true that a lot of our history is like the clock starts ticking when the settlers arrive, and then like you learn about Indigenous people in regards to their encounter with the settlers.

And often, I think, as curricula have gotten better like about how horrible and oppressive that encounter was. But of course, thousands and thousands and thousands and thousands of years of history of all kinds of different societies, all kinds of different languages and practices in all kinds of different regions, with all different kinds of climates, having lives and having societies, and that we don't talk about a lot.

And so, I really have been enjoying this fantastic new book called “Origin,” which is a genetic history of the Americas. It's by an associate professor of Anthropology at the University of Kansas named Dr. Jennifer Raff. It's about the peoples of this continent prior to being colonized and settled by the Europeans, and about the origins of those peoples and the diversity of those peoples. And I've learned a ton from it.

There's a very provocative sort of thesis at the core of it, or at least sort of like argued for about where those first peoples came from, and how long they've been here. And when I first read the review in the New York Times, it really piqued my curiosity. So it's a great pleasure to have Dr. Jennifer Raff on the program. Welcome to WITHpod.

Jennifer Raff: Thank you so much. I really appreciate being on here.

Chris Hayes: So the title I have in front of me is anthropological geneticist, and I'm just curious, let's just start, what is that? Like if you say, what do you want to be when I grew up? I want to be an anthropological geneticist, which you are, what is that?

Jennifer Raff: Yeah, it's not really a household term, is it? So an anthropological geneticist is the flavor of geneticist who studies the past using genetics, we could say that broadly, but does so with sort of an anthropological framework. So my training is in both anthropology and biology. My doctorate was a joint doctorate in both fields.

Chris Hayes: Technically, what does that mean? Like, how do you do that in terms of, obviously, like, so if you're studying genetics of people now, like if I can do the 23andMe thing, I can take a DNA swab, send it in. The Anasazi people that may have made those cave dwellings, right, they're not here anymore. So there's just a technical question of like how do you go about technically doing the work that you do?

Jennifer Raff: Yeah. So the human genome actually is an archive of our population histories. All of our ancestors who have contributed to our genomes, you can look at their histories using just basically by sequencing DNA, or genotyping DNA, looking at specific variants across the genome, and using population genetics then to work with that DNA and compare it to other populations and other individuals and say, “Okay, I can see which or I can recreate the point at which these lineages last shared a common ancestor.” And you can kind of do that going farther and farther back into the past.

You can model other evolutionary forces like gene flow, right? So did these two populations encounter one another and have children together? You can reconstruct all of that using population genetics.

Chris Hayes: Could you do that 20 years ago?

Jennifer Raff: You could but in a more limited way. So the major thing that has propelled this field forward in recent times has been the development of really sophisticated techniques for coaxing whole genomes, or at least genome-wide information out of ancient remains. And as much as that, it's also the bioinformatics techniques that allow you to, say, distinguish ancient molecules from modern contaminants which are everywhere.

And so, these kinds of developments, which have been propelled by some really creative and brilliant researchers, has made it possible for the field to access genetic information in the past in a way that's never been possible at this scale.

Chris Hayes: Okay. First, I want to just ask like a dumb question because, again, this is not an area that I have any particular expertise in. But when you say genome, what is the genome?

Jennifer Raff: Yeah. So the genome is all the DNA present in your chromosomes, right? And your mitochondrial genome is a separate genome that's much smaller, and that's all the DNA present in the mitochondria of your cells, which are maternally inherited only. Because if you think about, at conception, you've got the egg from your mom and the sperm from your dad, right? The sperm contributes chromosomes, but it does not contribute mitochondria. And so, that comes just from your mother. So mitochondrial genome is a record of maternal history. And the nuclear genome or the chromosomes is a record of everything else.

Chris Hayes: And the mitochondrial DNA, mitochondria are the little batteries of the cells, right? They're doing this this energy work. They have their own DNA. I only know that because my uncle is like a sort of world-renowned neurologist who studies rare genetic disorders pass through mitochondrial DNA, of which there are some. And so, you use both of those, right, to sort of do your investigatory work, both the nuclear DNA and the mitochondrial DNA?

Jennifer Raff: Yes. Mitochondrial DNA is a lot easier to recover from ancient remains because it's so much more abundant. If you think about you've got hundreds of copies per cell, right?

Chris Hayes: Right.

Jennifer Raff: And so, you're much more likely to be able to recover it from ancient remains than the nuclear genome, which you know, you've got two copies of each gene per cell. So it's much more common to get mitochondrial DNA, but it gives you a much more limited window on the past.

Chris Hayes: So we're sort of talking a little technique, I want to sort of start right with some political questions because this is contested territory in a political sense. And I mean, political broadly, not like in a partisan sense. But like when you talk about remains, right, like, those are the remains of some people. They are the ancestors of some present people, the ancestors of present people who lived on a continent that they inhabited, that was then colonized and settled, that then took by force, essentially, their land away from them, and resulted in the system we have today.

And your descendant, I understand, of the European settlers, you work in institutions that are, again, created from that world, right? Like, there's some question about like who do those remains belong to? Who's doing the research? Under what set of frameworks and assumptions about, quote-unquote, “native peoples” are they doing it? And I think you’ve just you talked about it a lot. A lot of the book is about precisely this, and how fraught and contested that could be, and I'd love to hear you talk a little bit about where you're coming from on that.

Jennifer Raff: Yeah. Thank you. And I'm so glad that you brought that up because it is so important. I don't think you can really understand the history of how peoples came to the Americas without also interrogating how we got that data, right?

Chris Hayes: Yeah.

Jennifer Raff: And so, one of the major themes in my book is precisely that. And from the beginning of the book, I'm talking about sort of my role in this as you know, I would say just a shorthand, I'd call myself a settler scientist, right? I'm the descendant of settlers who have participated in a system and a structure which has been very oppressive to Indigenous peoples. And this plays into this much longer history that goes all the way back to the beginning of colonialism in the Americas, where native peoples have been removed, or enslaved, or eliminated from their lands in order to make way for settlers. And the same thing has happened in the history of science as well.

So the study of Native American origins has been of interest to European settlers since they first got here and primarily because, at first, they were confused by who Native Americans were. They were not in the Bible. They had no idea who they were. Many questioned whether they were human even. And so, Europeans both questioned who they were, but also invented their own mythologies about who they were.

And one of them was this idea that the first inhabitants of the Americas, the people who made these amazing mounds that one can see, for example, in the Eastern Woodlands regions of North America, or the incredible artworks that you can see in the archaeological record, that they were not ancestors of, quote-unquote, “Indians” that the Europeans encountered. They had to have been somebody else, right? And because it's, frankly, just a really racist perspective and that has persisted to the present day in some forms, right? You go on to certain cable show and you'll see “The Lost Race,” “The Lost Civilization,” right. There's all these narratives out there.

Chris Hayes: Really. So just to be clear, look, the idea is there are these obvious signs of like incredible human civilizational ingenuity that are apparent in the physical record, right? You still see them today. But the people in front of us don't look like us, and we think they're essentially savages and not quite human. And therefore, just as a logical conclusion of our racism, couldn't have done this. So we must reverse engineer a backstory about essentially people that look like us, right? Some like lost tribe of us that ended up there to make all this cool stuff that we have to admire.

Jennifer Raff: Yeah.

Chris Hayes: Because it couldn't have been these people who we think poorly of?

Jennifer Raff: Exactly. And in fact, it was essential. That narrative was essential to colonialism. And Andrew Jackson even cites what we call the myth of the mound builders in his Indian Removal Act, and that the justification --

Chris Hayes: Wait. Really?

Jennifer Raff: Yeah, it's there. So this --

Chris Hayes: Wait. Like, what did he say? What?

Jennifer Raff: Yeah. I don't have the exact text in front of me. We'll have to look it up. But he says that there was a lost civilization that was wiped out, and that's used as a justification. It's incredible.

Chris Hayes: Wow. This was common enough belief that it was in the ether as understood like there were white people here before that did all this cool stuff, who were then replaced by these people that we've encountered.

Jennifer Raff: Yeah. And the exact identity of sort of this lost race, it varied, right?

Chris Hayes: Right.

Jennifer Raff: So some people said they were ancient Atlanteans, or some people said they're ancient European, some said they were Chinese. It just depends on --

Chris Hayes: Right.

Jennifer Raff: But most agreed that they were probably white from Western Europe. And it’s incredible to me, but this idea persists today in some of this alternative history. But to bring it back to the non-alternative history, the scientific study of Native American origins, originally launched, in part, to address these questions. And as the discipline of archaeology professionalized, they came to the understanding, “Of course, the ancestors of present-day Native Americans made these mounds and were the first peoples here.”

But there was then this attempt to understand them in a racial framework, right? So who were they, what race did they belong to, who did they most resemble. And the discipline of the study of human crania and the shape of human crania really became important to this. And as well to study the human crania, there were researchers who would go out and loot cemeteries to get Native American skulls to measure and to put into these racial typologies. And in many ways, that informs the whole eugenics movement in some ways.

Chris Hayes: So that's sort of pseudoscience, which was really very popular in the sort of 19th century, as I understand it, and into the 20th century called phonology, which is this essentially totally discredited set of pseudo biology that sort of classified people into races, along racial hierarchy, we should note, based on like cranium measurements, right? That's roughly the --

Jennifer Raff: Yeah. And phonology is slightly different. It's kind of looking at little bumps and things, and telling about personalities. But craniometry or the study of the shape and its volume --

Chris Hayes: So that's different. Okay. I'm confounding them.

Jennifer Raff: Yeah.

Chris Hayes: Okay.

Jennifer Raff: But that was not just fringe science. I mean, fringe science, to some extent, there are some applications of it that we could get into. But the actual measurement of skulls and placing into typological categories and ranking of races, that was actually modern science in the 19th century and the early 20th century. That was it.

And so, I think it's really important to our discipline that we acknowledge this history and we acknowledge the damage that it did to Indigenous peoples. I mean, their ancestors were looted and put into museums or put into research collections, right? And these research collections, in some ways, did contribute to many scientific understandings of forensic and other important understandings of the past. But they also have caused great harm and distress to present-day descendants. And so, we have to grapple with that legacy. And there are plenty, I should say, plenty of my colleagues are doing just that. But I want to make sure that the public is aware of this as well.

Chris Hayes: So let's talk about the origins of the thing that you're studying, right, which is the people that lived on this continent earliest. So I guess let's talk about the sort of the story that I learned to the extent I learned any of this, right, the thesis about how did human beings end up in North America.

Jennifer Raff: Yes. So this is the story that I learned also. I mean, I think if you're our age, you've probably learned this in school, which is that the peopling of the Americas occurred about 13,000 years ago, give or take. And it was a small group of big game hunters who chased mammoths from Northeast Asia across a land bridge to Northwest Alaska, following the last Ice Age. And they traveled southward through a corridor that had opened up between two massive ice sheets that covered basically northern North America.

They invented these new stone tool technologies that are characterized by a beautiful fluted point, projectile point on the end of a sphere, which we call Clovis points. And this appears widely across the North American continent about 13,000 years ago, and these were the first peoples of the Americas. And by the way, maybe they hunted all these Ice Age megafauna to extinction, like giant mastodons and dire wolves, and so forth, that we used to see, that are now extinct.

Chris Hayes: And Clovis point is the name of the thesis, right? Like, that's shorthand. It's like the Clovis --

Jennifer Raff: The Clovis First model.

Chris Hayes: The Clovis First model. Okay.

Jennifer Raff: Yeah.

Chris Hayes: And just to go back one more step, and again, I know nothing essentially about this. So the first human being, homosapiens, like I guess I learned the immersion in Africa, like, has that been destabilized? Are we still --

Jennifer Raff: No, that’s still true.

Chris Hayes: Okay. Just checking. And then, obviously, they moved up from Africa through Europe and Asia. And then the idea of the Clovis First thesis is that they came over a land bridge that was essentially frozen during Ice Age, and descended down through Alaska into the rest of North America?

Jennifer Raff: Yeah. That's more or less that.

Chris Hayes: And then eventually South America, right? Like all the same genetic stream.

Jennifer Raff: Yeah. And it was a very rapid migration of people of the continents in this model very, very quickly.

Chris Hayes: 13,000 years ago?

Jennifer Raff: Yeah.

Chris Hayes: When did this thesis arise?

Jennifer Raff: So this kind of emerged, I would say, about mid-20th century, give or take, and it really helped sway over the field for much of the 20th century, the latter half of the 20th century.

Chris Hayes: Well, there must be reasons for it, right? I mean, there's some sort of evidentiary record that made this a compelling theory. What were the reasons?

Jennifer Raff: I would say the main evidence that rests on are these Clovis era sites, we call them Clovis era sites, these sites that are characterized by this toolkit, with these Clovis points, and they appear very rapidly all across North America, just a flash, right about 13,000 years ago. And so, it looks very much like this was the result of a rapid migration.

And adding to that, any sites which predate Clovis tend to be a bit more difficult to assess. Are they real sites? Are they not? Right? And archaeologists, they can be quite controversial. And so for a long time, any site that seemed to be older than 13,000 years ago was dismissed by the majority of archaeologists.

Chris Hayes: Right. I mean, because you got a weird thing, right? You've got this interplay between the theory and the data, where sometimes the theory can steamroll the data, precisely because the data itself is contested in the product of like a lot of uncertainty. So maybe again to dip back into the kind of like methodology here, like, how are we dating this stuff? And how short are we anyway when we're dating stuff?

Jennifer Raff: Well, dating, I could do a whole lecture on that. Dating is usually done looking at isotopes, radioactive isotopes, and the decay of these isotopes. So you think about carbon-14 dating, right? You look at the proportions of these isotopes, and that gives you a radiocarbon date. And then you can calibrate it by taking into account certain factors to actual years, calendar years. And the dating methods are quite good. It's the calibration that can give you some uncertainty. So you have a bit of uncertainty there, so you get a range of dates.

Chris Hayes: How big is that range of uncertainty, though?

Jennifer Raff: It really depends on what you're looking at, and how you're calibrating it, and how much data you have, and how good your methods are. I mean, I guess the unsatisfying answer is it depends. But it can be up to a couple hundred years, couple of dozen years, just kind of give or take.

Chris Hayes: But not thousands of years. I mean, I guess, to my point, because the thesis that you're advancing in the book, which is distinct from the Clovis First thesis, is quite a bit different in years. And so I guess the question is like how much is the product of mythological refinement? How much is the instrumentation or estimates of dating are getting more precise over time? Or how much is it the kind of classic Kuhnian paradigm shift, where the way that scientists think about a problem is so overdetermined by the theory, that people are essentially throwing out data to keep the theory going?

Jennifer Raff: It's all at once. So yes, methods for dating are getting more precise. Methods for calibration are getting more precise. But also, we're finding more sites, and we're finding older sites and these sites that are quite a bit older. And paradigm shifting, one could argue, are not accepted by many archaeologists because they say, “Well, there's this problem with the dating,” or “This site lacks definitive evidence of humans.”

So think about it this way, when you have a rock and it's been broken, the question is, did humans break that rock intentionally or accidentally, or was it broken by natural processes, or even monkeys --

Chris Hayes: Right.

Jennifer Raff: -- as in South America, right? These are not easy necessarily to distinguish between.

Chris Hayes: So we had a moment, we were in the foothills in Sedona, and we were with a guide who picked up a rock that had been perfectly smooth, like flattened. And she was like, “This is clearly the work of humans. And it was used probably as like an Indigenous stone to grind meal, right, from corn.” And she gave it to me and she said something like, “Obviously, it's done by humans.” I was like, “I don't know.” I was like, “Was it in a riverbed?” Not that I was like denying it, just like it struck me this question of like, “Oh, is that an arrow point?” or it sounds like indisputably clear in either direction, right?

Like, when you say you've shown up at a site, and it's like even that is contested. Again, we're just talking about the evidentiary record. We're not even talking about the theory, right? Just like I show up somewhere, I find what looks like an arrowhead, is it an arrowhead? Like, that's not necessarily going to be consensus bedrock in your field, right?

Jennifer Raff: Right. And I want to make it very clear, I am not an archaeologist, if you ever wondered.

Chris Hayes: Right.

Jennifer Raff: That’s outside my ability. But the archaeologists are very, very good at identifying, “Okay, this was clearly made by intention, human attention.” And they have bulbs of percussion and things that they look for, right. But sometimes it can be a little unclear, right? And what is the difference between an artifact made by humans and a geo fact, right, made by natural processes? And so, archaeologists have very rigorous standards and they can argue about this quite a bit.

And that is the case with some of these really early sites, the ones that date to 20,000; 30,000 years ago. The majority of them are not indisputably human caused, right? There's no hearth there. There are no human remains buried there. There's no beautifully shaped arrowhead or projectile point. There are broken rocks. There are things that are suggestive, but not necessarily definitive, and that leaves a lot of room for questioning. But I would argue, there's at least one site that I find pretty compelling. It is still controversial, but we can get to that if you want.

Chris Hayes: Yeah. Hey, wait a second. Wait a second.

Jennifer Raff: Sure.

Chris Hayes: You just did a great job of a tease. Let's take a quick break and we'll talk about that site after this break.


Chris Hayes: All right. So tell me about this site that you think is compelling.

Jennifer Raff: Okay. I find this very compelling. So this is a site that was recently published, in fact, right at the end of the last stages of my book. This paper was coming out so, of course, I was freaking out about it. It's at the White Sands National Park, and it's the White Sands site or White Sands locality too as it's called.

Chris Hayes: Is that in New Mexico?

Jennifer Raff: Yeah, New Mexico. It has this incredible record of human footprints, and not just footprints, but trackways, long links of people walking on what would have been a muddy bank of a lake. And it's not just humans, but extinct Pleistocene megafauna. These giant mastodons, these giant sloths were walking and crossing each other's paths. And these tracks persist for 2,000 years. People were using this for 2,000 years. It's really incredible.

And they have been dated by means of little seeds that have been embedded in the footprints to between 21,000 and 23,000 years ago. That is older than any other site that we have really found to be persuasive to the majority of archaeologists. And this site itself, there's a lot of archaeologists who still question it. But to my mind, it's very compelling. And it's making me rethink a lot of my models and try to understand how can this fit in with the genetic evidence, which actually shows a different history.

Chris Hayes: Okay. So I mean, I guess the question is like how disputed are the footprint?

Jennifer Raff: They're human. They're very clear. And they're not just clearly human, they are children's footprints mostly. There are young people and children running around. There is a beautiful trackway of a person. It could have been a mother or father's, a small person walking for, I think, up to a kilometer. And at some point, this person puts down what they were carrying it, and it was a little child. And the child walks along beside them for a little bit, and then they pick them up again.

Chris Hayes: Wow.

Jennifer Raff: I mean, it just gives the most incredible insight into the past. It's a window into the past. It just gives me chills when I think about it.

Chris Hayes: So you say that it’s intention with what. Like, that's the world you work in. What does that record say about the Clovis First thesis and the sort of genetic diffusion that happened in North and South America?

Jennifer Raff: Yeah. So I kind of think about it in three sort of phases, if you will. And the first is sort of the formation of the gene pool that gives rise to Native Americans and other populations. And that took place in Asia. And it was really precipitated by the contact between a group of people who would have been ancestral to present-day East Asians and a group of people in Siberia, which we are calling genetically, it's not a great term, but the ancient North Siberians. And these two groups come together, and there's gene flow between them.

And then they become isolated, and they're isolated for several thousands of years. And this period of isolation, which we can detect genetically, it's very clear, lasts between -- it kind of depends on how you do your models. And when you're talking about dating with genetics, it's even more sloppy in some ways than dating with carbon-14. But the isolation may have persisted between maybe 26,000; 20,000 years ago.

But it coincides with the peak of this global climactic event, which we call the Last Glacial Maximum. And that's a period when, globally, the Northern Hemisphere especially was very cold, very dry. There are not a lot of resources for people to make use of. And so, we see populations around the world retreating into rifugia, these little geographic areas where there's more abundant plant and animal life. And so, we think that's what's going on with this ancestral population. They are hanging out somewhere during this time, where they can find more resources, animals, wood to burn, plants to eat.

Chris Hayes: Do we know where that is?

Jennifer Raff: Well, we don't really know. For me, the most plausible place is the southern margin of central Beringia. So if you think of the Bering Land Bridge, which was a connection, of course, between Asia and North America, it was actually really more of a lost continent. So it's like twice the size of Texas, if you can imagine it, really big. And the southern margin, the central portion of it, a paleoclimatic reconstructions have shown that it was a decent place to live. It would have been warmer. It would have had animal and plant life, a lot more water. And so, that is currently, to my mind, the leading candidate where people were isolated.

Chris Hayes: So during this period, that land bridge is like, just to be clear, I mean, it's stable. It's actual land, right?

Jennifer Raff: Yeah.

Chris Hayes: Like, it's a stable place that has a habitat and an ecology, and like, you can live there. And it's not like, “Oh, well, it's cold enough, so we can cross over.” It's like just a place, right?

Jennifer Raff: Yeah, it's absolutely a place. And I would argue if this model is right, we can think of Beringia as a homeland, not as a bridge, right?

Chris Hayes: Right.

Jennifer Raff: Yeah. So while they're isolated, though, some interesting stuff is happening genetically, and we don't have a really great handle on this right now. But it seems to be that several branches emerged within this population. So one branch goes back to Siberia and repopulates it, because Siberia had been, we think, mostly abandoned during this period.

And then other branches move farther east into North America, if that's where they were in the first place, right? We don't really know. We have no archeology to show us that people were right there because --

Chris Hayes: Right.

Jennifer Raff: -- it's at the bottom of the ocean.

Chris Hayes: Right.

Jennifer Raff: Yes, exactly. So we need submarines or something, I don't know. But the splitting of these populations into different branches, what is going on there? We're not really sure. But we know that at least one of these branches then moves farther into the Americas, farther south and becomes the ancestors of Native Americans.

Chris Hayes: And when you say we know, like that is fairly definitive consensus in the genetic record?

Jennifer Raff: Yeah. The genetic record shows that very clearly. There may have been other ancestors too. So this is where you get into some of the really exciting and murky areas of research right now in the field. We see a connection, a genetic connection between South Americans, some South Americans and Australia Melanesians. That is fascinating. It's not for reasons that immediately come to mind like some kind of Trans-Pacific migration. The genetic record does not match what we would expect from that. We don't see patterns of genetic variation that would have supported that model. Instead, you can kind of imagine two other scenarios.

One is that this original population in Beringia had some folks with that ancestry, and it just kind of trickled into some populations, or there was an earlier migration of people that got into the Americas before they were blocked by ice, right? That would have had to have been before 25,000 years ago when these ice sheets are closed. They closed the access to the rest of the continents. And maybe that group is population Y or what we call this ancestry, and that they then interbred with the main migration of Indigenous ancestors or first peoples who we see genetically appear to have moved into the Americas starting about maybe 18,000; 17,000 years ago.

Chris Hayes: Okay. So I just want to distinguish here between like what sort of field consensus and what sort of not, right. So the kind of idea of some Siberian East Asian group that then comes into North and South America, that's fairly consensus established in the genetic record, right?

Jennifer Raff: For now, yes.

Chris Hayes: For now. Again, I--

Jennifer Raff: I mean, I have to qualify everything. I'm a scientist.

Chris Hayes: Of course. No, that's fine. That's good.

Jennifer Raff: Yeah.

Chris Hayes: I'm in cable news, so we do the opposite. We speak with total authority with everything. Okay. So then the question, as I understand it, it’s basically what you call population Y. Was there a group before them? Right?

Jennifer Raff: Right.

Chris Hayes: I mean, that's sort of what it boils down to. Am I tracking this correctly?

Jennifer Raff: Yeah. And that is not clear. The population Y ancestry is there. It's in South Americans. I think it's pretty well established at this point. But it's strange. It's present in different proportions and different genomes. And there's not a clear understanding right now of how it got there. So there's these two models out there that could explain the evidence, but we need more data in order to really figure this out. And we just don't have the genetic sampling, right now to figure this out.

Chris Hayes: Why not?

Jennifer Raff: Well, that gets back to what we were talking about earlier. There is a very poor relationship right now between Indigenous peoples and scientists, non-Indigenous scientists. And that is entirely our fault, the scientist’s fault, right?

Chris Hayes: Right.

Jennifer Raff: Because there has been such a bad history of exploitive research and abusive research, and research without consultation. And I mean, I could get into a lot of cases of this, that it gives many tribes no reason to want to trust us with the remains of their ancestors, no reason to want to work with us. The situation is improving a lot, and the field has changed a lot in recent years. I don't want to give the impression that all scientists are bad.

Chris Hayes: Yeah. Well, there's just a legacy here’s a pretty bad one. I mean --

Jennifer Raff: Yeah. And trust to us is hard to earn, right? And it needs to be continually earned, and we have to do a lot of work to repair these relationships. A friend and colleague of mine likened it to a house with a poor foundation, that we have to rebuild that foundation, and that is going to take a lot of work and a lot of time.

I will say, I mean, there are tribes who are delighted to use genetics as a tool for understanding history. I work with a number of them. There are other tribes to whom DNA is sacred and the remains of their ancestors are sacred and shouldn't be disturbed. And that is absolutely fine and should be respected. So all of these factors together have resulted in a very uneven sampling of genomes across the Americas.

Chris Hayes: I see.

Jennifer Raff: Yeah. And so, especially in present-day United States, there's not a whole lot of ancient genomes. There are a few and each one that we have has given us incredible insights into the histories. But there's a long way to go before we have a complete knowledge of this, and we have no idea what we're going to find out.

Chris Hayes: We'll be right back after we take this quick break.


Chris Hayes: To get back to the sort of Clovis First theory, what are the deficiencies of it? And what do you think is the more compelling version now?

Jennifer Raff: Yeah. I mean, I guess I should stress there are some archaeologists who still favor a rather late model, so maybe just before 14,000 years ago, and they do that because of, I would say, their rigor in assessing the evidence of these pre Clovis sites. And there's another group of archaeologists actually on the opposite extreme, who think that people got here super early, like maybe as early as 130,000 years ago, which that's a whole other subject, right? That's a very, very small group of archaeologists.

The majority of archaeologists and geneticists look at these pre Clovis sites, these sites that predate 13,000; 14,000 years ago, and there are a number of them. And they say, “Okay, this is evidence that people were here perhaps by 16,000 years ago, maybe earlier. And the route by which they would have had to have taken to get here that early would have had to been along the West Coast by boat, rather than through the interior of the continent, through this ice-free corridor along the Rocky Mountains.”

If that is true, it matches the genetic evidence pretty well, which shows a diversification of lineages and rapid movement of peoples. So to my mind, the genetic evidence and this sort of what we call this West Coast migration, or some people call it the kelp highway hypothesis, because people would have been encountering similar resources all the way up and down the West Coast, including kelp. That is the most evidence from both fields kind of fits together into a nice story that way. But White Sands may change that, right? White Sands challenges that. So we have to think about that.

Chris Hayes: Wait. I want to make sure that I'm managing all this in my brain. So the Clovis First is over the land bridge 13,000 years ago, right? Quick diffusion, this kind of arrowheads that show up in a bunch of places quite quickly. The kelp highway is through boats down the West Coast,like 16,000 years ago?

Jennifer Raff: Yeah. That route would have been first available to people. That ice sheet would have been melting back from the West Coast enough for people to travel that way, starting maybe about 17,000 years ago. So it fits pretty well with the patterns that we see in the genetic record.

Chris Hayes: I mean, if you just take a step back, again, I'm sort of looking at this from a sort of epistemic standpoint, but like how much different very complex science has to be put to work here, right, to reconstruct this because like there's a climactic question there that's being constructed by climate historians, right, who were reconstructing like when did the ice sheet, which itself is like dependent on a bunch of like technical measures.

Like, just to take a step back from sort of epistemic perspective, I mean, again, this is hard stuff, right? This is like trying to reconstruct like what happened 16,000 years ago. I mean, that's an obvious point. But just the different fields of science that have to be brought to bear on that, when you talk about like the climactic record, like that's someone is reconstructing that with a whole set of methodologies that are complex and definitely use modeling, right? Like, all of the data inputs here are going to be difficult to obtain, difficult to analyze, subject to fairly complex modeling, right, to get it right. And then you're putting a bunch of those different kinds of things together, like there's going to be a lot of uncertainty inherent in this undertaking.

Jennifer Raff: Yes. To put it mildly, yes.

Chris Hayes: Yes.

Jennifer Raff: And I inhabit this space where I'm trying to understand all of these different things, and probably, I don't know, not doing the best job in any of them. So trying to put these pieces together to tell the story to non-scientists, it's very challenging.

Chris Hayes: Well, that's why it's so interesting too because it's like trying to build one of those physics bridges in eighth grade out of toothpicks, right? Because you're trying to kind of create from the data you have in the different fields and the sort of cutting edge of what we can do, both sort of in dating things and modeling things. Like, the maximum load bearing theoretical structure or a story on, again, like the pyramids, you're setting the pyramids, like they're there. Right now, you could go to them. And that's not what you're working with, or people in your field broadly are.

Jennifer Raff: Yeah, it is an incredible challenge. And then again, made more challenging by the fact that we're limited in the number of genomes that we have to bring to bear on this, right, far, far fewer genomes to reconstruct this history than we have for, say, European history, right? And that's a whole thing too, right, the intensity of interest in various fields. So it is very difficult.

And I think that's why over and over again, when I write on the subject, I stress what we don't know. And I stress the fact that this book is not intended to be the final word on any subject for two reasons. First of all, Indigenous peoples have their own origin histories. And they may or may not agree with what we're reconstructing from these, right?

Chris Hayes: Correct.

Jennifer Raff: And that's really important to acknowledge and respect. And second of all, this field is changing so fast. Every time, it seems to me, there's a new genome published, it changes our models. And so, it may be in subtle ways, but it may also be in big ways. And same thing with the archaeological record, right, White Sands completely threw me for a loop. I was like, “Oh, my God, I'm going to have to incorporate this somehow now.”

And so, what I want to give people is a framework for understanding where we're at right now and how we got here in terms of our understandings and the data that we've collected. And then when they hear about new findings, “Oh, okay, this is what that means. And this is how I should change my thinking,” because it's going to change. I mean, I hate to say it, my book is going to be out of date very quickly. So how can I add value to this conversation? That was a bit of a challenge.

Chris Hayes: What are the stakes here in getting this right? I mean, that's sort of a silly question because what are the stakes of any kind of definitive knowledge? But I guess, what compels you to do this work? Like, why is it important for us to understand that?

Jennifer Raff: I think it's important to, returning back to the thing that you said at the very beginning of our conversation, to acknowledge the fact that Indigenous peoples have a history here that's very long. And when we find more evidence, it keeps showing that it's earlier and earlier. So Indigenous peoples have this history that is really ancient. And if we're only teaching about history starting in 1492, or to be fair to historians, of course, many of them grapple with earlier histories. But I don't know how much that's filtering into the public schools or --

Chris Hayes: Yeah.

Jennifer Raff: And so, it's important that we get that history correct. And it has great implications for, I think, how we non-Indigenous peoples understand our own history. It's not that this was new terra when our ancestors came here, right? It's really important to recognize and respect the fact that Indigenous peoples have their ancestry stretching back in these lands for millennia, right, very, very long time.

How do we understand that? Well, I'd like to understand it personally from a scientific perspective, bringing all these different kinds of data to bear, to get the most accurate picture we can, and then place that understanding alongside these Indigenous traditions so that people can see there are many different ways of understanding the past, and which one that you prioritize depends on the evidence that you prioritize.

And I think that maybe sounds a little wishy-washy, but I’ll just point out that archeologists do exactly that. right? Which sites that they find legitimate really color the models that they subscribe to. And some say that the Americans were people late, some say the Americans were people super early, right? It just depends on which sites they consider to be legitimate.

So I think genetics has a really strong role to play here because it's a separate kind of data. It tells us about biological histories. It tells us about relationships between peoples in the past, between ancient peoples and present-day descendants. And we can get at some really interesting questions like is this individual buried in this grave with this other individual? Are they genetically related to each other, right?

Chris Hayes: Right.

Jennifer Raff: That can be really useful to know.

Chris Hayes: I mean, the two things that strike me, one is the sort of sheer pluralistic multiplicity and bounty of Indigenous peoples across these two continents in this world that I think you kind of learn about. You learn about the Aztecs and the Incas, I think. I hope people know the Maya, Aztec, Incas. You learn about sort of Indigenous, like the big sort of empires and civilizations. But even just like more localized, just how diverse and diffuse, and populated and interesting that these worlds and continents were.

But I think also, I mean, the profound question here, right, is about like the human family. And I think that how different are we, how related are we, how connected are we to each other, like the kind of intuitive mythology or religious belief of Adam and Eve that we're all from the same human family, which is again the tradition I grew up Catholic. How do you think about what the genetic record says about human commonality, or what do you think about in this sort of broader, almost philosophical, almost spiritual sense, like, what's the difference between what you're doing and what those cranium measures we're doing, both at the level of rigor, but at sort of deeper level about what it means about human being and human difference?

Jennifer Raff: I also grew up Catholic, so I have that framework as well.

Chris Hayes: Yeah.

Jennifer Raff: But I would say that from a methodological perspective, when we're using genomes, whole genomes, to look at biological relatedness, that is the highest scale resolution we can possibly get, right? It does not get any more precise than looking at complete genomes.

When you take a step back from that and when you're looking at, let's say, cranial measurements… and I might get myself into trouble with some colleagues here, but when you're looking at cranial measurements, you've got a lot of different factors in between the genes and the phenotype, right, what you're seeing. That could be things like interactions with the environment, developmental influences, all these things can shape one's cranium.

So just from a purely scientific viewpoint, again with my apologies to some of my colleagues, I really think that genetic data is the most precise, the most powerful way to look at these relationships. And what genetic data shows us, what the study of genomes from peoples all across the world show us is that we are very closely related, that patterns of genetic variation, in fact, do not map onto these races that were constructed in the 19th century, well, in a bit earlier, of course.

Chris Hayes: Correct.

Jennifer Raff: And that these so-called biological races are not concordant with the genetic evidence at all. That is a hard concept for a lot of people to wrap their brains around because we see phenotype, we see differences, we are primed to do that. And from those differences that we see, we have constructed these racial categories. But in fact, when you examine them with genetic evidence, they break down. And that is not a particularly controversial thing for me to say, but I expect I will get a lot of comments about that.

Chris Hayes: That's remarkable, right? I mean, this is like you work in, as you said, the highest resolution data we have about human similarity and difference, which is the genome. And we operate in a world of these constructed categories that are, I mean, they're sort of based on phenotype, but really they're based on ideology. I mean, they're sort of a combination of the two, right?

The one drop rule that produce blackness in the American South is not actually based on phenotype. It's actually based on ideology because that's, hence, the entire very complicated history of passing and all that stuff. So it is interesting to talk to someone who actually looks at it at this level, that looks at human development, the human family to say that like, “Yeah, like what we do is just like orthogonal to the categories, the racial categories of phenotype that are basically the product of a specific intellectual project that started around the 17th century in Europe.”

Jennifer Raff: Absolutely. And the thing is it's not that we say that there are no genetic differences between people. I mean, that's absurd. Of course, there are, right?

Chris Hayes: Yes.

Jennifer Raff: And you can use those genetic differences to understand histories. That's the whole point of what I do. But I guess the broader perspective on this is that those genetic differences are not concordant with thinking about humans in a racialized way, in a type of logical way. It just doesn't work. It's way more complicated than that. And I hope that the work that we do will help people to understand that. I think that this is going to be a very long term proposition, though, because these categories are so ingrained in our culture, and they're so persistent.

Chris Hayes: Right. I mean, there are census categories, and again, they exist for a reason, right? Because like, I mean, again, there are different ways of dealing with the sort of duality the fact that race is both constructed and real, which it's like real in the sense that it produces social outcomes and social hierarchies, and is reinforced by all kinds of different norms, customs, laws, a million different things. But also that it's not like embedded in genetic reality, in some sense of like the thing, the reality being out there in the world.

And navigating between those two becomes very complex because, in here, the Field sisters’ great book “Racecraft,” I'm basically just ripping off, that there's the trick of what they call conjuring, right? When you're talking about race, you’re reifying at some level, or contouring it, but it's also crazy to be like, “Well, I don't see race and everything is just the same.”

Jennifer Raff: Yeah.

Chris Hayes: And navigating those two twin things is something we try to do on the podcast a lot, but it's very tricky stuff.

Jennifer Raff: It is very tricky. It's very difficult to talk about. And then, of course, I have to be mindful of my positionality as a white woman, right, and talking about this. I can say things that other people can look at and say, “Well, of course, she can get away with saying that, right? Look at her privilege, right?”

But speaking as a scientist as well, I would say that, well, this is an interesting thing when it's applied specifically to Indigenous peoples, because in the Americas being, quote-unquote, “Native American” is often racialized. And I am going to recommend that everybody read a book by Kim Tallbear which is called “In Native American DNA,” because she breaks down that concept very well and she has some really brilliant insights into this.

And I just want to say, I mean, I don't speak for tribes, I do not want to venture out of my lane here. But I will say that it’s not the role of us, geneticists, to define who is and is not Indigenous, and hard stuff, right? So you cannot take a DNA test to prove that you are Native American.

Chris Hayes: Right. This is the Elizabeth Warren problem and I saw people making this point. And again, people remember the Cherokee Nation, lots of Indigenous folks just being like, “That's not the way it works.” Again, it's just a different way of saying the same thing you just said, right, which is that these categories are not genetic categories. Fundamentally, they're not genetic categories. They're categories that are the function of human society, human history, human self-identification and community, a bunch of social factors, sometimes created against groups, will sometimes fuse and form by the group itself. None of that has to do, at all, with genes or the genome.

Jennifer Raff: Right. So tribes use, like you said, a variety of criteria for determining who belongs to their membership, right? That is their sovereignty. They get to decide how that works. It is not to say that if you take a DNA test and it shows that you have Indigenous ancestry, or I should say, let me be more specific here because it can get very confusing.

Native Americans today have ancestry from many different populations, including the first peoples of the Americas, and including a bunch of different populations that came up here at the start of colonialism or as a result of colonialism, right? So they're quite diverse genetically. And you can look for ancestry from the first peoples and you can find it. And many families have traditions of descent from those first peoples. And therefore, they use genetic ancestry as a tool for investigating those traditions. That's fine.

But what you can't do is then say, “I am Native American,” right? I need to stop talking about this at this point because I am again venturing out of my lane.

Chris Hayes: Right.

Jennifer Raff: There are ways to reconnect, right? There are great harms done by colonialism that have separated people from their families. And genetics can be a way to start that reconnection process.

Chris Hayes: Right.

Jennifer Raff: It is not for me, as a geneticist, as a specialist in this field to tell anybody that, “Yes, you're Indigenous,” “No, you're not.” That is not my role. And yeah, it's so complicated to talk about.

Chris Hayes: Yeah, it is complicated.

Jennifer Raff: I feel uncomfortable talking about it.

Chris Hayes: I think rightly because, again, it's not in the realm of science. I mean, that's the point, right? It's not a scientific determination. Science can produce a set of data that can inform all kinds of forms of human practice. But that's just the beginning and not the end. And again, that sort of brings us back to me, like, I don't know, this is just maybe just a naive thing to say, but what I come away from, from reading your book, and when I come away from that scramble up the cliff, to look at the cliff dwelling and these ruins, it's just a real sense of awe.

A sense of awe at human ingenuity and the human will to survive, to propagate, to live, to draw, to trade, to worship, to do all the things that humans do. I mean, I don't know, it's like I think about whoever those first peoples were like, man, that was a tough journey. And like, what an incredible thing that they pulled it off. I mean, I don't have any rooting interest other than the sheer scope of human ability is truly an inspiring thing to reckon with. And when you think about how difficult it would be to travel over these distances, and to live in these places, and to make a life for you and the little kid that you're carrying, and then putting down and then picking back up. Like, there's something very beautiful about that to me.

Jennifer Raff: Oh, yes, I 100% agree. And I am so lucky to be able to work in this field and work on this every day.

Chris Hayes: Good job, humans. You really crushed it. Good job, humans, 16,000 years ago. You really crushed it.

Jennifer Raff is an anthropological geneticist. She's Associate Professor of Anthropology at the University of Kansas and author of The New York Times bestseller “Origin; A Genetic History of the Americas.” It was a really a great pleasure to talk to you. Thank you so much.

Jennifer Raff: Thank you so much, Chris.

Chris Hayes: As always, tweet us with the hashtag #WITHpod, email, and be sure to follow us on TikTok by searching for WITHpod. Send us all your feedback for this conversation or any that you've listened to.

“Why Is This Happening?” is presented by MSNBC and NBC News, produced by Doni Holloway, Tiffany Champion and Brendan O'Melia, engineered by Bob Mallory, and features music by Eddie Cooper. You can see more of our work, including links to things we mentioned here by going to

Tweet us with the hashtag #WITHpod, email “Why Is This Happening?” is presented by MSNBC and NBC News, produced by Doni Holloway, Tiffany Champion, Brendan O'Melia, engineered by Bob Mallory and features music by Eddie Cooper. You can see more of our work, including links to things we mentioned here, by going to