American History Hit - The First Americans

Episode Date: December 22, 2022

Modern humans thrived in the Americas for thousands of years before the first European colonists arrived, but how and when did they get there?What's more, did their arrival spell disaster for indigenous megafauna such as giant ground sloths and wooly mammoths, or was there another culprit behind the mass extinctions across North, Central & South America?This is an episode is from our sister podcast, The Ancients. Host Tristan is joined by Professor David Meltzer, an archeologist from Southern Methodist University, to explore the nature of human migration into the Americas and how scientific developments now allow us to discover more about those very first Americans.For more History Hit content, subscribe to our newsletters here.If you'd like to learn even more, we have hundreds of history documentaries, ad-free podcasts, and audiobooks at History Hit - subscribe today! history documentaries, ad-free podcasts, and audiobooks at History Hit - subscribe today! Hosted on Acast. See acast.com/privacy for more information.

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American history is a vast subject, even looking back to Euro-colonial days. Never mind the more fundamental origin story much further back. When did the first human beings even show up on the North American continent? How about the South American one? For many, it's a surprisingly controversial issue these days, with new science and new thinking being done in many quarters, which challenges all that general grade school stuff we were raised on, or at least I was, that mankind simply walked over back around the last ice age, chasing woolly mammoths with spears and clubs, and whoops, here we are, a whole

new world. Didn't really go like that. And today we have a chance to learn why and how. Allow me to introduce my esteemed colleague at History Hip, Tristan Hughes, who hosts a remarkable and long-running podcast series called The Ancients, which I highly recommend wherever you get your pods. And today, in just a short moment, we'll be hearing his discussion about this fascinating history. Tristan, welcome to American History Hit, Long Time No See. Long Time No See, my friend. I am so happy to be here. This is the crossover at History Hit that we've been waiting for. So I'm so excited.

And I'm just delighted to hear you seem to be doing so well, too, so energetic. Thank you very much. I think the crossover we rated for was in a pub last week in London, not to brag, but I was over there, meeting the history hit folks and drinking bitters, which are bitter. It was a great night out at the pub in East London last week, and it was really good to have you over in the UK, and I hope that we'll meet up again in a pub for more pints when you're next back over in the UK or when I'm over in the US. Very nice. Well, we cut all this flattery out of here, so let's just cut to the chase here.

Tristan, this is an incredible subject that I, for one, find really confusing sometimes and need to be guided through. The assumption has always been that there was this moment, pre-recorded history, of course, when mankind sort of chasing his prey across the bridge between Asia and Canada today, you know, finds himself in a new world and begins to settle. That's sort of the assumption that we get. I think it was in fourth grade. I was taught that.

Well, it's so interesting, isn't it, Don, with this subject. And this is one that I've only recently started to learn more about us. And I'm no expert, but it's been a pleasure to interview scholars. about it. And you know, that great land bridge, the Bering Strait, the Bering Land Bridge connecting Alaska to Eastern Asia at the time of the last Ice Age. It is a fascinating story about how humans first came to what we now call North and South America and what we know about it. And from what you hinted at there, when you're at fourth grade, the thing with this field, with the story of the first humans in the Americas is that it has evolved so much and so recent.

just like a few years ago because of these developments in scientific techniques in genomics, but also advances in archaeology too. And so that is allowing these incredible scholars to learn more about when and how these people came down into the Americas during the Ice Age period. In just a few short moments, as I said, we'll be listening to your discussion with Dr. David Meltzer, who's at Southern Methodist University, big-time anthropologist there, who's going to, take us through this, but I just want to impress upon the audience that this really does stir the pot. That assumption about when people come has this wide-reaching implication, you know, about our understanding of what happened here on this continent before the Europeans come. And it really is

important. It resonates throughout the whole understanding of American history, honestly. It absolutely does. And also something which is really key in understanding this period as well. And as you say, there's still lots of debate as to when and how people come down. into the continent, but also the importance of climate at this time too and how that also influences when and how the nature of this migration, this prehistoric migration occurs, and then people spreading out across the Americas. And of course learning more about this subject, you'll also hear in the episode the importance of communication, the importance of making sure that all the research around this is done closely connected with the Indigenous American community too,

and the incredible Indigenous American anthropologists and archaeologists who are also working in this field. It's the stake in the ground for the real understanding of what really happened here before the Eurocolonists come over. And that's really, really important and has huge implications, as I say, well, let's not keep them from this conversation that you're having. Without further ado, allow me to introduce an episode of the ancients featuring our friend and colleague Tristan Hughes.

David, it is great to have you on the podcast today. Thanks for inviting me. You are very welcome indeed. I've been waiting to do a topic on America for so long, and I'm so glad that we're now doing this one. Because when looking at when the first modern humans reach the Americas, David, it feels like this is an extraordinary field where even recently, in only the last few years, the wealth of knowledge available is just growing and growing. It's a really exciting area of archaeology to really look into, and anthropology. Well, absolutely. You know, there's been a sea change just in the last decade or so, which is a combination of both advances in archaeology.

We're finding more and more ancient sites. But at the same time, revolutionary developments in genetics, which have enabled us to literally get into and answer a question that I've been wondering about for, well, a very long time. I'm not going to tell you how old I am. And that is the population history of the first peoples who came to the Americas with DNA, and specifically with ancient DNA and ancient genomics, we can reconstruct who these folks were, where they came from, or at least who they're related to, among other populations in Ice Age, Asia and Northeast Asia.

We can approximate when they got here, but of course, you know, it's the archaeology that actually gives us reliable and secure dates. So this combination, this wonderful combination of new advances in genetics and archaeology have really enabled us to, in a really substantial way, kind of narrow the window within which this whole process took place. And what are these sorts of developments in genomics are we talking about in recent years, David?

So with genetics, we've long understood that there are certain corners of the genome where we can trace back specific single locust markers, like, for example, mitochondrial DNA and the Y chromosome. These are inherited matrilineally or patrilineally, respectively. And we've known for a long time that Humans, modern humans, came out of Africa. And I suspect you've talked in the past about things like mitochondrial Eve, which enables us to sort of trace back the sort of female lineage to an individual who lived in Africa some two to 300,000 years ago, plus or minus, right? And to a male. But that's only two individuals.

The human population history is this incredibly complex skein of people and groups who mixed, mixed, ad-mixed, got isolated from one another, the later gene flow. It's a complex story. With the development of genomics, the ability to see the whole genome, and more specifically, the development of ancient genomics, the ability to extract from human skeletal remains, genomic signatures, we can now start to piece together who these people were, who they're related to, the sort of budding and lineage splitting, admixture coming together later, on of these populations as they moved out of Africa across Eurasia, interacted with Neanderthals and Denisovans, and ultimately found themselves on the edge of the Bering Land Bridge

and then pushed into the Americas. It is quite something. And I love that idea, David. For what you said there, it's a lovely example, isn't it, where it's combining these new advancements in science with archaeology to get more of a picture of this particular field, it's so exciting indeed. I mean, if we therefore do talk on the archaeology and then go onto the genomics and how it works hand in hand, as you've hinted out there, when looking at the archaeology for this field, what's the earliest secure archaeological evidence that we have

for early modern humans in the Americas? And I say secure with a key emphasis on that word. Yeah, I was just going to say, yes, and you underlined it and italicized it, and that was important because there is, and in fact there has been for the better part of a century and a half, considerable controversy over when the first people came into the Americas. The controversy had its first resolution in the 1920s when it was demonstrated for a fact that people had in fact arrived by the end of the Pleistocene. That subsequently triggered another question and debate, which was, okay, well, so they got here by the end of the Pleistocene. Did they get here earlier? And that issue took another, oh, half a century to resolve, maybe a little bit more, with the discovery of the Monteverde site. This is work that was done by Tom Dillahey in southern Chile, which demonstrated pretty clearly that people had been in southern Chile as long ago as, say, 14.5,000 years ago.

Which obviously raises the question, well, if they're in southern Chile 14.5,000 years ago, my goodness, what time? and would they have come across the Bering Land Bridge and made their way down through North America. So obviously the implication is that there ought to be older stuff. In the last decade or so, there have been quite a number of candidates put forward that suggest evidence of humans, more or less reliable evidence of humans in North America by 15, 15 and a half, plus or minus, we're archaeologists. We like to deal it plus or minus, right? And it seems more or less reliable. It actually matches up more or less well with the genomic evidence, recognizing again,

that genomic evidence is not very good on age in any sort of precise way. It gives you sort of ballpark figures. And so the secure evidence seems to be pointing to an arrival south of the massive continental ice sheets that covered much of Canada during the ice age sometime after around, say, 15,500 years ago. There are, however, much earlier claims, which at the moment are sort of being held in check. It's not entirely clear that they're secure, to use your very good term, and we're waiting. Archaeologists have a long memory. It's sort of an occupational hazard, right?

We think about things of the past, and we've seen so many sites come and go that we've become fairly skeptical about claims of truly great antiquity, claims that, say, push human presence in the Americas back 10,000 years or more, we're not entirely, well, some people are cynical. I'm just skeptical, right? So if you've got a claim that pushes back what we understood to be the case by, say, 10,000 years, I'm not unwilling to consider it, but I really want to see the evidence. And I want to be convinced by the evidence. And I want to have compelling evidence if we're going to take that sort of chronological leap,

as it were. It sounds from what you're saying, David, that the archaeology, and you've mentioned this in your papers that you've written, can provide the minimum age. So we've got a site. It proves that people, humans, early modern humans are there at that time, but they were probably there before then. Well, that's the issue, right? Is that you're never going to find the very first footprints of people in the Americas, right? The odds of finding that very first site are infinitesimally small. So you know that they were there when you have a site, that they were there. by that time. Obviously, they came earlier, and especially if your site is in Southern Chile. So if they're

in Southern Chile by 14,500, they had to have come across much earlier. And that's the nice pairing and synergy of the genetic evidence with the archaeological evidence, which is that genetics gives you a maximum age to complement that minimum age that archaeology provides. Because what genetics does is it says, okay, this is the point that we estimate this population, who would then go on to cross the Bering Land Bridge and make their way into the Americas, separated from their northeastern Asian relatives, and split off. Now, the moment that they sort of split off genetically does not necessarily correspond to the moment that they physically packed up and said, okay, it's time to head to New York, right? Rather, it's the moment where the two populations

became isolated from one another, and at some point thereafter, the ones that were headed to New York left. So that gives us a maximum age, just as archaeology gives us that very minimum age. And somewhere in that window, and that window at the moment is around 8,000 years. It's between about 23,000 plus or minus, that's our genetic maximum estimate. And about 15, 15 and a half thousand, that's our archaeological minimum estimate. So somewhere in that 8,000 year window, which happens to coincide precisely with the last glacial maximum, just a complicated. matters. This is a period of time where you don't expect people to be moving across the vast frozen north. But apparently it was. So in that window is when that process took place.

You mentioned so much there. I want to definitely get into that geographic context very, very soon. But I've got to ask a couple of questions first, because you also mentioned these earlier in your answer there. The first one, all actually, I've got to talk about is in regards to genetics, and I guess ethical questions surrounding it now, because how important has it been We're now looking at genomes and genetics in this area for collaboration with the indigenous American community. It's absolutely vital. You know, archaeologists, biological anthropologists, we haven't always done right by the indigenous

peoples of the Americas. And that's changing. You know, I've been involved for the last, oh, I guess a dozen or so years with a number of studies of ancient genomes. and we've made an effort, and I say we, really, this is to the credit of my collaborator, Eski Wilderslev, at the Center for Geogenetics at the University of Copenhagen. Eskies really made a tremendous effort to reach out to the Native American communities. We understand that so far as our interests are, they may not overlap with the interests of the indigenous peoples whose histories we wish to understand. On the other hand, we also feel that we have things that we can offer in terms of understanding their past and contributing and helping them to understand that past.

And the best example would be the so-called Kennewick Man, the ancient one, which was in legal limbo for a decade or more and was the subject of a legal tussle between scientists who wish to study the remains. I was not part of that group. I mean, I wanted to study the remains, but I understood that these were also remains that had been claimed by five Northwest Coast tribes who wanted Kennewick to be returned to them and reburied under the conditions of the Native American Graves Protection Repatriation Act.

It was all sort of stuck, and it was stuck because the courts and scientific decisions should never have to end up in court and have a judge who knows nothing about the science decide how things should go, but the courts had decided that Kennewick was not Native American. We had the opportunity to look at Kenowick's genome, and it was unequivocally Native American. And so we were able to contribute through the genetic study, the genomics of Kenowick, that we were able to show that he was Native American and that among his descendants were

the five claimant tribes in the Pacific Northwest. So in that case, doing the genetics and the genomics had a real practical, substantive payoff and value to the tribes, just as it helped us get a better understanding of an individual who had lived over 8,000 years ago in this region and see how he fit into that larger pattern. So those kinds of efforts, which were collaborative, we received permission. and in fact one of the claimant tribes actually provided DNA samples for us to compare to Kenwick. Those kinds of collaborations can really have positive benefits. It's wonderful to hear you say that positive, how that in itself is helping drive so many advancements in this field,

and hopefully we'll continue to do so in the months and the years ahead. Just going on from that, something else I'd love to ask about before really delving into when these first modern humans reached the Americas is what you also mentioned to, your previous answer, which was regarding footprints. Because recently last year, we had a chat with Professor Sally Reynolds about the new discovery of footprints in New Mexico. I'd love to ask about your thoughts around this, about this new discovery, what it is and the significance of it for this field.

As it happens, I do fieldwork literally across a fence from that footprint site. That footprint site is at the White Sands National Park. and I've been doing field work on the White Sands Missile Rage. And a couple of years ago, I knew about the site. I'd heard about the site. And so we just hop the fence and wandered over to look. It's an interesting locality, but maybe for your listeners, I should sort of give a little bit of the background here.

This is a really interesting site because a series of human footprints, human trackways, along with the tracks of other animals, including giant ground sloth and mammoth have been founded. in this area. And the tracks were dated. And actually, what they were dating was, obviously, you can't date a footprint, but what you can date is little bits of vegetation that got sort of tromped down by the people. And those dates came back surprisingly old. Specifically, they sort of range in age from around 21,000 years ago to about 23,000 years ago. It's one of those cases where suddenly we had all sort of assumed and believed and had evidence to suggest that people were here

as early as 15, but now we've got to push it back 8,000 years and does that work or not? Well, here's the thing. Nature has a mischievous streak, and we've been fooled before. So the operating principle, when we hear about a site that is going to push human antiquity back substantially, our operating principle is trust but verify, right? I trust the folks who are doing the work. I know they know what they're about because, in fact, some of my colleagues are on the team that work there. But you've still got to verify that nature has not pulled any fast ones. And the fast ones here are really down to the dating.

They're dating a plant. It's an aquatic plant that absorbs dissolved inorganic carbon, which has the potential, and I'm underlining the word potential here, it has the potential to give you dates that are older than they ought to be. So you really want to understand and be very, very secure in your understanding of the dating. Is it reliable? Is it accurate? And does it date the event in question? After you address that issue and if in fact it can be demonstrated that it is as old as advertised, there's still a couple of other issues that are really puzzling to me. as I hopped over the fence and I wandered over to the site, I'm looking around, you're literally on the floor of an ancient lake bed.

There's nothing there. And look, I'm an archaeologist. If I have a site where people have been coming back repeatedly to over 1,000 to 2,000 years, I want to know what is it about this place? Are the resources here? what brought people back to the spot repeatedly over more than a millennia? And then the next question is, okay, why didn't they leave a single artifact behind? If you come to a place repeatedly over 1,500, 2,000 years, how is it you manage not to drop a darn thing on the ground? There's no artifacts there. There's nothing there, right? And I got to say, I've also dug through those same sediments. And I am,

literally 100 meters away. We had a trench in the same deposits 100 meters away, same deep deposits, and we were taking samples. And we were sort of perplexed because we're pounding our sampling tubes into the sidewalls of our trench. And literally, it took rock hammers and sledgehammers to sort of chip out the dirt. And I was thinking to myself as I'm wailing away at the wall of this trench, how did they find footprints in this stuff? How do you excavate down through what's essentially the equivalent

of dirt concrete and find something as fragile, vulnerable as a footprint? I don't know. I read the articles about it. And when I went out to the site, I could see these big blocks of the same sediment that we were in in our trench. And they'd been excavated with what they refer to as a dirt rated chainsaw. I've never excavated with a chainsaw, I have to say. So that was the new one on me. But how do you find footprints when you're excavating with a chainsaw? I mean, the whole thing, I don't doubt that these are absolutely honest players and they're pros, every one of them. But I sure want to know more about this site before I'm going to say, okay, the dates are good, the footprints are real. They were wandering around the landscape with mammoths and groundsloss.

I get all that. I'm in. And as we now delve into how these first people, early modern humans, made it across the Americas. Just preceding that, this idea of when and how there are still these questions that, as you say, you have the minimum age with the archaeology, but there's still, even with these new discoveries, there are still hints of doubt to exactly when these first early modern humans really did venture. It seems like we have an approximate thousands of years dating range for that, but that is just it at the moment. It's still an approximate. Well, that's it. I mean, look, if this site, if all the T's crossed and the eyes are dotted and it proves to it. be as old as it is, then it just means that we've been wrong and we need to readjust our thinking. And I'm perfectly okay with that. But when you're going to, you know, the old phrase, right,

extraordinary claims require extraordinary proof. This is an extraordinary claim. Let's give it the extraordinary proof. And then we'll just rethink what we thought because clearly we hadn't been correct before. That doesn't bother me at all. I mean, that's the whole point of advancing the science, right? Absolutely. Absolutely. Well, let's therefore move on because you did mention it earlier. I'd love to really We're talking now about the geographic context of this time period that we're talking about. And first off, you mentioned the name earlier. What is the last glacial maximum? So the ice age, the Pleistocene, begins approximately two and a half million years ago.

And there's a whole series of repeated episodes of glacial periods when global temperatures drop. You have massive ice sheets move out of the far north, down latitude. And then you have interglacial periods. We are in an interglacial period. But at the time that this whole scenario and story of the peopling of the Americas was taking place, the world was moving into the grip of the last major glacial episode of the Ice Age, of the Pleistocene. So people are in far northeastern Asia, as best we can tell archaeologically, by around 35,000 years ago. So it took a long, long time for modern humans to make their way out of action.

Africa, you know, bear in mind, we are tropical creatures, right? It took a very, very long time for us to move out of Africa, get into the far north, be able to sort of weather glacial conditions at 55 degrees latitude, 60 degrees latitude, 65 degrees latitude. And that doesn't happen until much later in prehistory, like I said, around 30, 35,000 years ago. We have people in the far north at actually latitudes of about 70 degrees. They are literally. right on the Bering Sea. So at that point, and right after that point, the world starts to sort of slide into this really cold period that will, that we refer to as the last glacial maximum. It is essentially the coldest episode of the last portion of the Pleistocene. Global

temperatures will drop substantially. You have a massive ice sheet, actually two massive ice sheets, that will grow, one over much of Canada, from Newfoundland and Labrador, all the way west to basically the border between British Columbia and Alberta. And that ice sheet, known as the Laurentide Ice Sheet, will ultimately join up with,

and a butt, a massive ice sheet that grows as a series of mountain glaciers that coalesce over British Columbia, and that's known as the Cori-Irean Ice Sheet. With those two join up, and about one another, you've basically got 3,000 miles wide of ice, which reaches from the Pacific coast to the Atlantic coast. It reaches from the Arctic Circle down to central Ohio and portions

of the northern, now United States. In places, it is several kilometers thick. So it is a massive block of ice. It's insane to think that nowadays. And with the same time as these massive ice sheets, that it's so much of what is now North America. The Americas at that time weren't their own separate continent. Were they connected to Asia in where modern-day Alaska is? Right. That's the thing. If you lock up that much water on land, all these ice sheets are a function of precipitation, snow and rain, falling over the northern latitudes. If it then locks up as ice, if it freezes as ice, it doesn't get returned to the oceans, right? So the high, hydrological cycle is interrupted. You interrupt the hydrological cycle and ultimately build an ice

sheet that's, again, 3,000 miles wide and several kilometers thick. That's an awful lot of the ocean water that doesn't get returned to the ocean. When that happens, shallow areas of continental shelf become exposed because sea levels are dropping and sea levels dropped worldwide on average, though it varied tremendously depending on where you were on a continent, on average, you know, 130 or so meters. You drop sea level that much, you're going to expose large areas around each continent of shallow continental shelf, but more importantly, from the story in terms of the story of the peopleing in the Americas, you're going to expose the shallow shelf beneath the Bering Sea. If you drop sea levels just 52 meters, the Bering Sea becomes a lot of the Bering Sea.

is dry land. You drop it 130 meters, then you've got yourself a huge land bridge that connects up Northeast Asia and Alaska. And don't think of this land bridge as some sort of rope bridge that you're crossing the Amazon and you're kind of hanging on and you're walking, you know, one foot in front of the other very carefully. If you were moving from Northeast Asia into northwest, North America across the Bering Land Bridge, you probably had no idea that you were crossing from one continent into another because the Bering Land Bridge itself was a thousand kilometers wide. So if you're just walking down the center of it, you have no idea that you've left one landscape behind and you're moving into a completely new one. Now, of course, here's the complication.

During times of maximum ice on land, you have lowest sea level. That enables you to walk into Alaska. But once you're in Alaska and you're looking south, all you're seeing in front of you is the massive ice sheets, right? So you've got to wait. It's kind of a two-step process, depending on the timing. If you come across the land bridge in the depths of the last flacial maximum, the coldest portion of the ice age, what ice volume is at its maximum extent? You're stuck there until the ice begins to melt back and retreat. When that happens, there are two potential routes that will open up that will allow you to get from Alaska down to mid-latitude North America. The first route that opens up comes down the Pacific Coast.

That route is opened by around 16,500 years ago. The other route that will open actually opens at the junction of where those two ice sheets had bumped into one another. Basically runs down the spine of the Rocky Mountains between British Columbia and Alberta, and we refer to it as the ice-free corridor. As the ice sheets begin to retreat, this corridor opens between them. Now, we know that in glacial geological terms, that corridor probably opened physically around 14.5,000 years ago, plus or minus. But biologically, what's the first thing that's going to grow in a recently deglaciated landscape? It's going to be mud and it's going to be water.

That landscape's not going to become revegetated, let alone have animals in it for a substantial period of time. So it looks like that corridor, while it was physically open, as early as 14.5,000 or so years ago, it was not a biologically viable route until probably as early as around 13,000 years ago. So do the numbers. If you've got people in Southern Chile at 14.5, they did not come down through the ice-free corridor because it wasn't available to them at the time they must have come across the land bridge. So that, in turn, has shifted a lot of our archaeological attention to the Pacific coast as the route that the First Peoples took into the Americas. Well, if we stick on the land bridge first of all before talking about this Pacific Coast route,

so is it therefore viable before 16,000 years ago when those ice sheets were impenetrable for people crossing over or coming over the land bridge, that these early Homo sapiens could have gone across the land bridge. thousands of years before and just had to stay in that region for quite a long period of time because they literally couldn't go any further? Or do you think it was more a brief stop in Alaska and actually, and then they continued down when the Pacific coastal route opened? Right. Well, that's the question we're all asking, right? There is some genetic evidence of what's been referred to as the Beringian standstill, where basically folks get up into this region and then they just cooled their heels for several thousand years. And estimates range

from as little as 2,400 years to as 9,000 years, but we just don't know, right? We've not found any archaeological evidence that would directly test that hypothesis that people had been hanging around in either on the edges of the Bering Lampbridge or on the Bering Lampbridge itself. Obviously, the Bering Lamp Bridge is now drowned. So any evidence is going to be under 52 meters of water, so the likelihood of finding that is quite limited. But we still haven't found any archaeological evidence of people close to the land bridge at that time. Okay. So if people were hanging out in that part of the world, the earliest states that we have in Siberia are around 16,000 at a place called Doctai Cave, but that's still a thousand or more kilometers away from

the land bridge itself. The earliest evidence that we have in Alaska is around 14,200. So, yeah, it's really hard to say where people were and whether they, in fact, came across the land bridge and had to cool their heels in Alaska for thousands of years, or if it was, as you also suggested, a sort of one-shot deal, they came across the land bridge just as the Pacific Coast route was opening up, and so they didn't have to pause. They didn't have to stand still. They could just keep coming all the way down into the lower 48. Or, I mean, let's take our footprints in white sands. If they were here 23,000 years ago, well, they could have actually crossed the land bridge at that point. And there would not necessarily have been any barriers to their southward movement.

I mean, there would have been ice on the landscape, but it would not necessarily have restricted their ability to come down into the lower 48. So, you know, the answer is we don't know the answer. But we sort of know that at the moment, we know the parameters based on our current knowledge. but, you know, when you work in the science and current knowledge is only as good as today, tomorrow it might give you a different story. Well, indeed. I mean, what is fascinating to therefore think, if you put yourselves in the footsteps, in the footprints, literally footprints of these early Homo sapiens coming to the Americas, you know, if they are going

down that Pacific coastal route and they get away from the ice sheets, David, do you think it would have felt like a whole new world? I mean, what sorts of geographic landscapes are we taught? talking about, what sorts of animals and the like would have greeted these early Homo sapiens well, as soon as they got past that ice barrier? Yeah. So actually, coming down the coast, it would not have been too terribly challenging or as challenging as it might be.

Let me actually give you an analogy and then we'll talk about Pleistocene. And the analogy is going to be British settlers landing in Virginia in 16th century, 17th century. They had no clue. They didn't know what to do. You had colonies that got lost. You know, the famous Rono colony disappears. Why? Because suddenly they're transported from an economic system where they understood how everything

worked. They had markets, they had villages, they had towns, they knew crops to grow. And they're basically transported. I don't know. What does a transatlantic ship crossing take in those days? Months. Oh, I wouldn't ask me, that's too modern for me, I'm afraid. But let's say it would take a long time.

It takes a long time. And suddenly you're deposited on the outer banks of Virginia or North Carolina. And they say, okay, see you later. We'll send a ship back in a year. And the ship comes back in a year or two or whatever it was. And they're all gone. What happened to them? Well, I suspect what happened to them was they suddenly got dropped into a completely alien environment.

And they had no idea what to do. I don't know that that's the cause of the disappearance of the Rono colony. But it's certainly a good possibility. Now, let's go to the Pleistocene. You've got people that have been in Northeast Asia for some time. They've been working their way across the Beringland Bridge. They understand the environment. It's got mammoths.

It's got horse. It's got giant bison. They can go out to the coast and they can see the coastal resources. As they're moving south down the Pacific coast, they're seeing the same kinds of things. Now, obviously, as the coastal route just opens, there's not going to be a whole lot of mammoths wandering around on the beach of the Pacific Ocean. Okay. But as groups have adapted to that coastal environment, say on the edges of Beringia, on the edges of the land bridges, they're working their way south, it's not going to change that much. So it's actually fairly easy to move through environments, to move across distances, so long as the structure and the resources of the environment have not changed dramatically. These folks were not picked up by a helicopter in Asia and dropped off in Texas. So they're working their way into the continent. Now, what happens is once they get south of that ice sheet and they turn inland,

now that's more of a challenge. Imagine what it's like to come into an environment where you've never been before. It's completely unfamiliar. You are seeing plants and animals that you don't know whether they could feed you, help you, cure you, maybe even try and kill you, right? The first time somebody saw a rattlesnake, what did they do? Oh, what a wonderful noise that snake is making. Let's go take a really close look, right?

You only do that once. You may not be given another chance. So, you know, they're coming into a completely new land. And as they go further and further south, it becomes increasingly less familiar. So the process of landscape learning, figuring out how to survive and indeed, thrive in this new landscape must have been a process that was at once challenging and at the same time well within their capabilities. Mind you, these are people whose ancestors had crossed Asia. These were by no means cultural dopes. They knew how to hunt. They knew how to gather. They knew how to

experiment. They knew how to observe. You want to find out if something poisonous or not? You give it to your younger brother. And let's see if Mikey gets sick. Are the animals eating those red berries If they are and they're not keeling over, maybe they're okay for us. So you're learning as you're going. You know how to make stone tools. You know how to find good stone sources, right? You drop down into a river valley. And if you see some really high quality stone that you want to use to make your tools,

well, if you see it in gravel in the river valley, go up valley. And maybe you'll find the outcrop where the good stuff is, right? the mountain of, you know, wonderful chert that you can use to make stone tools. So these folks were extraordinarily adept at adapting and extraordinarily adept at adapting to new landscapes. So this was not like getting on a boat in Liverpool and ending up in Virginia and having no clue about anything, right? These were folks who were working their way slowly into a landscape and learning as they

went and ultimately thriving. Ultimately thriving, as you say. it's quite interesting you say that that learning curve, that probably that very deadly learning curve which occurred. I mean, what sorts of animals would they have been coming, I guess if we're talking about a hunter-gatherer society at that time, what sorts of animals would they be coming up against in this new landscape? Yeah, so there are large predators on this landscape.

At the end of the Pleistocene, or toward the end of the Pleistocene, we know that some 38 genera of large mammals go extinct, and among those 38 genera are seven genera of, of large carnivores. So you've got saber-toothed cats, you've got cheetah, you've got giant short-faced bear. Now, the question that people have always sort of wondered about is, were these animals in any sense dangerous to people

and impediment to people, if people ever interact with them? We don't have any archaeological evidence. In some cases, it may well be that some of these large, nasty predators had gone extinct by the time humans arrived. But that's not to say that Earth, herbivores aren't just as dangerous. You've got mammoth wandering around the landscape. And if mammoths behaved anything like their modern elephant relatives, they were not a species to be trifled with. As folks who today live in areas that are occupied by elephants, folks in Africa, will tell you,

elephants don't behave like animals, they behave like enemies. And if mammoths were like that, That would have been extraordinarily dangerous as prey and potentially dangerous if you tried to sort of mess with them. I mean, think about it. You're coming into a continent and you've got to stick with a sharp rock on the end of it. This is not, you're well equipped for the Pleistocene, but are you well equipped to take after and bring down five, six, seven tonne animals? This episode will return after this short break. If the archaeology is therefore not there at the moment, I know this is something that you've done some work around and kind of linking into that. This whole idea of these hunter-gatherers leading to overhunting these big

creatures, sometimes herbivores, such as the mammoths, and leading to their extinction. But how likely do you therefore think that argument is that these first homo sapiens in the Americas would ultimately lead to the extinction of these megafauna? I don't think there's really evidence or reason to think that people were responsible for the extinction of all of these animals. It's been estimated that when Clovis people arrived, there were anywhere from 100 to 200 million of these large mammals on the landscape. Yet when you systematically look at all the sites for which it's been claimed that humans were preying upon these animals, we quite literally have only 16 or 17 now.

We've just got another site added to the list. 17 occurrences in which humans were clearly responsible in some form or fashion for killing, scavenging or dismembering the critter. So first point is that there's no archaeological evidence for it. Second, only five genera of these animals are found in those sites. So you've got mammoth, Mastodon, Gompathir, camel and horse. But what about the other 33 genera? There's absolutely no evidence that humans had anything to do with them, let alone were the cause of their extinction. And in fact, it appears as though most of these animals, or at least the majority of these animals, may well have disappeared before humans even got to the Americas. Now, the complication

there is that we don't actually know when all of these animals did in fact vanish from the landscape. We've got radiocarbon dates on about half of them that suggest that they did in fact survive up until, or at least approximately, the end of the Pleistocene. But for, for or the majority of them, they may well have disappeared, or we just don't know when they disappeared. So we can't really say that people were contemporary with these animals or not. It's also the case that the one species for which we do have substantial evidence that humans were hunting these animals, that species is bison, the American buffalo, we have abundant evidence of people hunting these animals, and yet bison are still around.

And in fact, Bison were not only hunted starting in the Pleistocene by some of the first people into the Americas, they were hunted over the next 12, 14,000 years by Native American groups out of the Great Plains. And ultimately, they were hunted almost to death by commercial hide hunters in the 19th century. And yet after all that intensive predation, bison still didn't go extinct. So we have 38 genera for which there's virtually no evidence whatsoever that humans were preying upon these animals. and they go extinct. And yet for the one species for which we have abundant evidence

of human predation, they don't go extinct. So the notion that people were somehow responsible for the extinction of all of these animals really doesn't make any sense from an archaeological perspective.

Does it therefore seem to make more sense that climate change is the real killer of these megafauna? Climate change, in fact, is involved in all of this, right? So climate change is the ultimate driver of all of these processes. It's the process that or the trigger that leads to humans moving into the Americas, right? Because you've got onset of last glacial maximum climates. You've got sea levels

dropping. People can come across the land bridge and so on and so forth. So yes, it's responsible for that portion of it. But it's also at the end responsible for a huge number of changes that will take place in the climate and in the ecology of the Americas, particularly North America, because, of course, as the ice sheets are retreating, there's all manner of changes that are sort of coming along with that ecological changes. So ecological communities and biotic communities that have been in place for thousands of years that had adapted to ice age climates will start to fragment and come apart. Different species will be responding to the increasing warming and other changes such as changes in seasonality, changes in the composition of grasslands. A colleague of mine

refers to it as a biogeographic free-for-all. Basically, the end of the Pleistocene is coming. There's substantial changes in the climate, and these will ripple through the whole ecosystem in, and basically it's every species for itself. They're all going off. They're dispersing. They're finding their new niche in these warmer climates. And so when everything gets pulled apart, that's going to endanger, that's going to destabilize ecosystems in a way that will impact the ability of animals to respond to these changes. And let me just give you an example from a recent paper that the Willerslev Group just published in Nature last year, which was a detailed study of environmental DNA recovered from throughout the Arctic. And one of the things that we were able to show in this paper was that in,

Far northern Siberia, the plant communities, the vegetation communities and the climate, basically there was sort of a lag. Everywhere else at the end of the Pleistocene, there's substantial changes going on. But for all intents and purposes, and I'm putting sort of air quotes around this, the Pleistocene hung on in far northern Siberia for thousands of years after it ended everywhere else. And what do we see? Late survival of mammoths and woolly rhino. Because the environment didn't change, right? The plant community stayed stable. So where we do have stability, yeah, everything hung on. In North America, where the end of the Pleistocene brought a wide range of ecological changes and climatic changes. I mean, think about just the weather effect. Ice sheets are just giant weather makers. If you have an ice sheet, parked over in Canada, it's going to have a profound impact on the climate south of there. Remove that ice sheep.

All sorts of things are going to happen. So with all of those sort of destabilizing processes taking place, animals are scrambling, and clearly, some of them, it got past their threshold to adapt, their tolerances, their adaptive challenges. And so, and it's important to add to this as well. So Extinctions is one end of that response. It's sort of the extreme consequence. At the same time, it wasn't just animals that were going extinct.

We had massive range changes. We used to have Caribou living in the southeastern United States. Today, they live in Northern Canada. They're having to respond. Ecological communities are changing. Smaller animals are going extinct too. It's not just sort of the big succulent animals that everybody envisions people going after giant game like ground sloths and mammoths.

Smaller animals are changing their ranges. Some of them are going extinct. Some of them are going locally extinct, but surviving elsewhere. So there's this incredibly complex set of changes that are taking place. So it's no surprise that at one end of those complex of changes, animals are disappearing. Thank you that explanation, David, because I was keeping thinking about animals and the like, because my mind is, for some reason, it's just keeping going back and back and back and back again, too, of all these megaphone and how they change at that time.

But there seems to be one animal from what you've been working on from your papers and the like, which seems to have been there from the start since the first humans arrived in North America and survives and adapts during these changing climate times. And it is man's best friend, dogs. So we do see that we see dogs since the start of Homo sapiens coming to the Americas. Yeah. So the dog story is a wonderful story. And this was, if you don't mind me sort of tooting our horn a little bit here.

You go for it. You go for it, Dave. It's all good. I've got the microphone. Yeah, so a few years ago, I was giving some talks at Oxford and visiting my colleague and friend Gregor Larsen there. We does dogs. And Gregor was telling me about their reconstructing the history, the phylogenetic history of dogs based on their genes. And he was giving me their estimated ages of when the dog populations kind of split from one another,

what the oldest dogs were in the Americas, the oldest dogs in Siberia. and he's giving me this timeline. And I'm looking at his timeline. I'm thinking to myself, oh, goodness, that looks like the human timeline. And then it finally dawned on me. I can be really slow at times. It finally dawned on me that, well, people can come to the Americas without dogs. But dogs aren't going to wander over to the Americas without people.

They're domesticated animals. And so we started to sort of play on the whiteboard in his office there. This is with Angela Perry, a PhD student of Gregors, who had just finished a few years earlier, who was an expert on the archaeological side of the dogs. And we realized that we've got a really nice sort of co-evolutionary story here where people will domesticate dogs somewhere in Northeast Asia. We don't know exactly when.

I'm going to leave that one to the dog people. But when people come into the Americas, it appears as though they brought their dogs with them because we see in the genetic record and the genomic record of humans these splits that are taking place as populations are moving further and further south into the continent, and we see corresponding splits in the dog populations.

So clearly, you know, as groups would come in and some of them would say, you know what, we're tired of hanging around here in California, we're going to go continue on down because we're due in Monteverdi in Chile at 14,700, so we need to get moving. So they take some of their dogs with them. And we see the isolation of these human populations,

the isolation of these dog populations, and it's showing up in the genome. record of both. So it makes perfect sense that they would come in to the Americas, that they came into the Americas with their dogs. Their dogs were, I suspect, part of the cultural repertoire. If you're coming in, this gets back to the issue of coming into an unknown landscape facing potential predators that you've never dealt with before. If you've got a dog, hey, that's a bit of defense right there. That's a warning sign and signal and system that you've got that you can use, right? So I suspect it was, you know, evolutionarily advantageous to the

first people into the new world to show up with their dogs, not just because, you know, everybody likes dogs, except for the people that like cats, but because dogs actually served a very useful purpose. And I'm guessing does the evidence, as these groups of people diversify over the years following their descent down the Pacific coast, as they start spreading inland across the Americas and I guess then reaching down to ultimately places like Chile through Mesoamerica and South America as they diversify

through all these parts of the Americas inland and further south I'm guessing do we see the evidence that I'm guessing the dogs stay with them and that's one question and the other question I guess because I've mentioned diversifying do you start seeing these groups of homo sapiens really emerging into distinct groups

so dogs and then distinct groups I'm asking about. Right so dogs So dogs are diversifying as well as they're moving into the Americas. And their patterns of diversification, chronological terms, are sort of matching up nicely with the diversification of human groups. And indeed, human groups are diversifying. But think of these not so much as, you know, we're not evolving new species. What we're getting are new populations emerging, which if they stay isolated for long enough,

will become distinctive genetically. And let me sort of clarify what we talk about when we're talking about distinctive genetically. When we're looking at these genomes, we are looking at neutral traits. It's been uncharitably referred to as junk DNA, but that's kind of a misnomer. This is DNA that does not have or is not seen by natural selection. All of us carry in our genomes, which are 3.2 billion base pairs. Of those 3.2 billion base pairs, there's about 20,000 to 25,000 genes. Genes are segments of that genome that have specific functions and purposes and that are sort of seen by natural selection.

But there's vast areas of the genome that doesn't at least at the moment appear to do anything at all. Those are the neutral traits. And that's the thing that we're looking at. So when we're looking at two different populations and we're saying they're distinct, it's not necessarily or even distinct in the sense of this group runs faster, this group jumps higher, or anything like that. They're distinct in terms of those long strings of letters that have no effect on a person's fitness, their health, their abilities, whatever, that are just part of that neutral

portion of our genomes. So, yeah, we see differences because these people are not. no longer part of the same gene pool. They're separating out from one another. And their, and mutations are constantly occurring in the neutral portions of the genome. So if you had a T or a G at a particular site, you know, now it's an A or a C. Okay. These are mutations that don't really have any consequences, except from the point of view of history and understanding who's related to who, if you see groups that have long shared strings of these letters in this neutral portion of the genome, you say, okay, well, they're pretty closely

related. When they don't share those long segments and they share only shorter segments over here on this chromosome and shorter segments over here, you say, okay, well, they must have separated from their most recent common ancestor a long time ago. Does that make sense? I think so. Yes. No, yes, it does. It's so interesting. I guess it's a great example, David, isn't it? About this recent, if we're going back full circle to how we started the interview, how recent advancements in genetics, in genomes, can start revealing so much about this aspect, this period of ancient history in what you've just said there, in trying to understand

more about how these groups, first of all, how they get to the Americas, and then how they spread out in the years following. Absolutely, absolutely, because what we can say, when we look at genomes from two apparently widely separated individuals, oh, these folks share long stretches of their genomic sequences. Therefore, even though I'm going to give you a specific example in a moment, but let me give you sort of the general idea, even though they're separated by two, three, four thousand kilometers, ten thousand kilometers, we can tell by virtue of these long shared sequences

and the relatively few differences in their sequences that they, in fact, are fairly closely related. Here's the specific example. So we have genomes from an ancient individual in Montana, dates to around 12,700-ish years ago, very closely related to an individual that was living in Nevada 10,700 years ago, so a couple thousand years later. And the both of them are fairly closely related to. an individual who is living in Southeast Brazil around the same time. So we can actually, with archaeology, we could never do this, right?

You find an artifact in Montana and an artifact in Nevada and an artifact in Southeast Brazil. You'd have no clue that these were made by populations that had a fairly recent common ancestor. And that not too long ago earlier, maybe just a few thousand years, they'd been part of the same population. So that's the one thing, right? Genetics enables us to make these long-distance links. The other thing this is telling us is that the first people that came into the new world were probably moving pretty fast, right? Because how else would you have a close relative from Nevada living in southeastern Brazil? There hadn't been that much change in the intervening period, right? They're fairly closely related genetically.

that gets back to the question of landscape learning. You're moving into, I mean, imagine going from Nevada to Southeast Brazil. Think of the environments you're passing through. You're going through the tropics, right? So you're going from essentially what's near desert, though it wasn't that rough in the place city. It wasn't a great environment, but it wasn't quite what it looks like today. You're going through the tropics. You're ending up in southeastern Brazil, and you're doing it sort of in the wake of a genomic eye, it's happening very, very quickly. So this gets back to the point that I was making earlier. These folks knew what they were about.

And apparently, there was some sort of incentive for rapid movement across the landscape, which raises the other question, what's the motivation? If you get south of the ice sheet and you land in Montana, I'd look around and say, you know, Montana's not such a bad place. Maybe I'll stay here. But these folks didn't stick around. Now, some populations did, right? It wasn't as though, you know, you had this single group that went all the way down to Tierra del Fuego in one shot.

No, you had populations that were settling in different areas, but some of them kept moving, and some of them kept moving south. What was the motivation? I don't have the answer, by the way. But if you think about it, one of the things that if you're a hunter-gather, and all these folks were hunter-gatherers, they're not farmers, they're not traveling with crops that they're planting or anything like that. If you're a hunter-gatherer, your best insurance is mobility. If you're a hunter-gatherer, what's important is not what's around you right now. It's what's going to be your destination when things go badly where you are right now. Where do you go when things go south?

Well, maybe in this case, you literally go south. There's so many questions that are still unanswered in regard to that, but it's wonderful to try and piece together that movement, as you say, and how quickly that movement could be, you know, from Montana to Brazil, then ultimately to Chile, over a pretty short amount of time when you look at it in prehistory. I mean, David, it just all sounds, you can see the passion in what you said just there.

It feels like with these recent developments, this whole field of the first people coming to the Americas, the first Homo sapiens, that in the immediate years ahead, not the far few years ahead, we're going to find out so much more. We're going to uncover even more information that's going to reveal even more about this really significant, important area in our prehistory. Absolutely. It's sort of a golden era in the sense that every new genome that gets sequenced is telling us things that we just didn't know before. And so I lecture on this topic. And every

year when I get to, okay, here's what we know, we take last year's lecture notes and we burn them. and we start afresh because it literally is almost a sort of a case of day by day. We've learned something new. It really is quite remarkable. The reach of the techniques and the technologies, the analytical techniques and technologies that we have today, which is not to say that good old-fashioned archaeology isn't helping as well because we're finding sites. People are making interesting arguments and claims about antiquity like White Sands footprints,

If those, in fact, can withstand critical scrutiny, then, yeah, we're going to have to sort of rethink a lot of what we've thought. So these are interesting times, no question. Indeed. And I wonder how many of your notes will be there, as you say, this time next year for your next series of lectures in the years ahead. Finally, you've written a book, a new edition on this topic, this ever-changing topic, these shifting sands. It is called David. Yes. In fact, it's funny. When the first edition of that book came out, I could see both genomic studies on the horizon and I could see ancient DNA on the horizon. The book was published in 2009 by 2010. That chapter in the book was obsolete. It was like, oh, I should have waited a year. But it's okay. Because when it comes to the genetics, it's never going to be up to date unless you're publishing your book online and virtually. And then you're just constantly every night putting in, oh, okay, well, there's been a new sequence, and here's now what we think is wrong, and here's what we still think is right. So yes, the new book, First People's

in a New World, came out last year through Cambridge University Press, and in it I try and indeed sort of update everything that we've learned in the decade or more since the first edition was published. And honestly, it was a wonderful experience doing the second edition, but it was exhausting because there was so much literature in both the genetics and in the archaeology, in glacial geology, in sea level studies that had come out in the intervening decade, dozen years, that it was a real learning experience and an exhausting experience because I hadn't realized I knew it was going to change a lot. I hadn't realized it was going to change that much. Well, David, as mentioned, it sounds super exciting indeed, and I can't wait to see where

things go in the future, as you said, this golden age in this area of prehistory in the first homo sapiens coming to the Americas. This has been a great chat and it just goes for me to say, thank you so much for taking the time to come on the podcast today. Tristan, I've enjoyed it greatly. Thank you. Thanks so much for listening to this special episode of The Ancients on American History Hit. If you like what you heard, please follow and review. And check out Tristan's feed on The Ancients too. There will be no episode of American History yet on Monday, but we'll be back as usual next. Thursday. Meantime, happy holidays.