09/15/2017

How Do We Study Ancient Americans?

17:37 minutes

Credit: Jordan Kirtley

The Americas were one of the last areas of the world to be settled by modern humans, and we know that one of the first migrant groups, known as the Clovis people, lived here around 13,000 years ago.

Beyond that, however, many details about these early Americans are still hazy. “We know very little about their habitation structure or social structure,” says Frédéric Sellet, an associate professor at the University of Kansas. “What we know is, we know what they ate. We know that they hunted mammoth, among other things, but also smaller animals. We know that they made beautiful stone tools.”

For Sellet, those stone tools are keys to understanding the Clovis and other early peoples. In particular, the Clovis left behind distinctly crafted stone spear tips, known as Clovis points.

At one Clovis site in Arizona — excavated in the 1950s — a mammoth was found with eight Clovis points, Sellet explains. “We think that that mammoth actually ran away and survived … so, the Clovis hunters never caught up with him,” he adds. “So, we know that they were throwing spears into the mammoth and probably quite a few spears in order to kill it.”

[A 14,000 year-old discovery emerges from oral history.]

To find Clovis tools, Sellet works with geologists to locate sediment layers from the period when the Clovis people lived. But even the help of science brings no guarantee of success. “Most sites that are that old are actually found by chance,” he says. “You have to understand that anything that is 13,000 years old is going to be buried very deeply.”

“For it to be found, it has to be unearthed by some heavy equipment, or we have to have a lot of erosion. In Kansas — in western Kansas — there is a lot of erosion; during the Dust Bowl, people found artifacts laying on the surface. But a lot of these have been picked up over the years, so they are getting very, very hard to find now.”

Jennifer Raff, an assistant professor at the University of Kansas, takes a different approach to understanding the Clovis and other early peoples. She’s a genetic anthropologist and studies DNA to learn more about human migration and ancestry. Right now, she says, scientists are working with a single Clovis genome.

“And that is because there’s really only one Clovis burial that we’re aware of, of a human individual,” she says, explaining that the individual, known as the Anzick child, is genetically similar to modern Native Americans.

“The Clovis peoples were the ancestors of all living Native Americans today,” Raff says. “If you look at the complete genome, we can actually detect genetic structure in Native American populations that tell us something about how they peopled the continent.”

The Clovis weren’t actually the first humans to settle in North America, Raff says. “It’s been really well-established archaeologically and genetically that there were people here prior to the Clovis culture. But they, too, were the ancestors of indigenous Native Americans, so we see very irrefutable evidence that all Native Americans are descended from the earliest indigenous peoples of the Americas.”

Rather than racing across the Bering land bridge, Raff says, these earliest people likely stayed in Beringia for thousands of years. “And they lived there until the pathways opened up — probably first along the West Coast — and then traveled down the West Coast as far as South America quite rapidly, and then peopled the continents across the land.”

To Raff, the ability to recover complete genomes from early remains has revolutionized our understanding of ancient peoples. “I think that one of the major things that we have learned from these new types of evidence has been that you can’t assume anything about human history,” she says.

While artifacts can signal how a culture was shared between populations, she explains, they don’t necessarily mean that people were moving around themselves.

“We see examples of contact between different cultures through the exchange of artifacts and material goods without there actually being any kind of biological consequence to that,” she explains.

“And then we also see the opposite in the genetic record,” she adds. “We see complete population replacements happening with very little archaeological evidence of that. So, you just can’t make assumptions about human history and about human biological history without really going out and looking at the DNA itself.”

—Julia Franz (originally published on PRI.org)

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Segment Guests

Jennifer Raff

Jennifer Raff is a genetic anthropologist and an assistant professor at the University of Kansas in Lawrence, Kansas.

Frederic Sellet

Frederic Sellet  is an anthropologist specializing in ancient stone tools and an associate professor at the University of Kansas in Lawrence, Kansas.

Segment Transcript

IRA FLATOW: This is Science Friday. I’m Ira Flatow at the Orpheum Theater in Wichita, Kansas.

[CHEERING AND APPLAUSE]

Now, if you’re could have seen Wichita and the Great Plains around 20,000 years ago, well, it was a real ghost town. In fact, all of the Americas was. It was one of the last parts of the world to be populated by modern humans. One of the first migrant group was the Clovis. They lived here around 13,000 years ago. And you probably remember learning in your elementary school science class about the Bering Strait land bridge. Remember about that? That the first Americans migrated from Asia over that land bridge? Well, like a lot of things, it turns out the story of how the Americas was populated might be a little more complicated.

[LIGHT LAUGHTER]

So who were these first Americans? How did they get here? And how do scientist piece together this mystery? My next guests are both anthropologists who study these questions, but they come at them from a different perspective, using different tools. Let me introduce them. Jennifer Raff is a genetic anthropologist. She’s an assistant professor at the University of Kansas in Lawrence. Welcome to Science Friday.

[CHEERING AND APPLAUSE]

Yes.

Frederic Sellet is an anthropologist who specializes in ancient stone tools and he’s an associate professor, also at the University of Kansas. Welcome to Science Friday.

[CHEERING AND APPLAUSE]

Dr. Sellet, let’s about the Clovis. We know the Clovis were spread out all around North America, right? But– but what do we know about how they lived, what their society was like? How do we know that?

FREDERIC SELLET: Surprisingly, we know very little. The first Clovis site was excavated in 1930, ’32. So for almost 100 years. And we know very little about their habitation structure or social structure. What we know is, we know what they ate. We know that they hunt mammoth, among other things, but also smaller animals. We know that they made beautiful stone tools.

IRA FLATOW: And, in fact, we have some. If they’re going to eat those mammoths, they had to go hunting for them, right?

FREDERIC SELLET: It would be a challenge to go after a mammoth, as you can imagine, without any weapon. So yes.

IRA FLATOW: Here’s some of these– describe these large stone tools. Look, like, that’s about a foot long.

FREDERIC SELLET: The largest ones are actually probably symbolic. They’re– those were not the ones used for hunting mammoths. But the smaller one– which is about four inches, four or five inches in length– that’s the one that was used for killing mammoth. So they– what they have, they have one very particular feature. That there is a groove at the base on each side. There’s a flake that was removed to kind of thin the point and make it easier to heft. And that’s the signature of the Clovis people.

IRA FLATOW: Because it really looks like they put a lot of work into that.

FREDERIC SELLET: They were craftsmans of tremendous skill. Yeah.

IRA FLATOW: So you tried to make some of these, reproduce these?

FREDERIC SELLET: It took me a few years, two or three years of practice.

IRA FLATOW: Now Jennifer, you approach it not from someone who’s digging up the tools, right? But you approach the Clovis– the genome of the Clovis, right?

JENNIFER RAFF: That’s right.

IRA FLATOW: What does this tell you about the lineage, then, of the Clovis?

JENNIFER RAFF: So we only have one Clovis genome. And that is because there’s really only one Clovis burial, that we’re aware of, of a human individual. And fortunately– I didn’t do the work. But another lab was able to recover a genome from that individual, who is now known as the Anzick Child. And what that genome tells us is really remarkable, that there were Native Americans– the ancestors of contemporary Native Americans look genetically similar. The Clovis peoples were the ancestors of all living Native Americans today. And that we can look– if you look at the complete genome– we can actually detect genetic structure in Native American populations that tell us something about how they peopled the continent. And it’s really a remarkable find. And it really changed the way that we understand the discipline today.

IRA FLATOW: So I’m– just to get that clear, they are the ancestors of Native Americans?

JENNIFER RAFF: Absolutely. And this is not something that was surprising to any geneticist who works in the field. But there were a number of alternative ideas about the ancestry of indigenous Americans. And the Clovis genome really put all of them to rest, I think.

IRA FLATOW: And now we’ve heard news reports and research and finds that there were perhaps groups of people in the Americas even before the Clovis. What’s your feeling about that?

JENNIFER RAFF: So, it’s been really well-established archaeologically and genetically that there were people here prior to the Clovis culture. But they, too, were the ancestors of indigenous Native Americans. So we see very irrefutable evidence that all Native Americans are descended from the earliest indigenous peoples of the Americas.

IRA FLATOW: How would they have gotten here? Could they have gotten here by boat? Would they make some boats instead of going over the land bridge? They would come by boats, perhaps?

JENNIFER RAFF: The current, most accepted model is– and you’ll find people who disagree about this– but the current most accepted model is that people actually moved into Beringia and lived there. It wasn’t just a land bridge that people raced across to get to North America. They actually lived there in what we would call refugia, or small little pockets of productive areas of land where there were animals living and plants. And that people could live there and survive the glacial maximum, where it was very, very cold and inhospitable. And so people lived there for some period of time. Genetically, we see evidence that suggests that the time that they lived there may have varied between, let’s say, 7,000, 10,000 years. Some people estimate as much as 15,000 years. And they lived there until the pathways opened up– probably first along the west coast– and then traveled down the west coast as far as South America– quite rapidly– and then peopled the continents across the land.

IRA FLATOW: How hard is it to find these tools? How do you know where– where to look in the ground for these sort of things?

FREDERIC SELLET: Well, I don’t. That’s my– that’s the problem.

[LAUGHTER]

IRA FLATOW: Let me go on to the next question! No, I mean–

[LAUGHTER]

But you found them! You did. You just– you weren’t just lucky. You had to have a– there’s a lot of geology to go through here.

FREDERIC SELLET: Yes. We have to work with geologists. They point to the right age of sediments. So we know where to look. It doesn’t mean that we’re going to find a site. Most sites that are that old are actually found by chance. It’s somebody is digging. Or– they’re– you have to understand that anything that is 13,000 years old is going to be buried very deeply.

For it to be found, it has to be unearthed by some heavy equipment. Or we have to have a lot of erosion. So in Kansas– in Western Kansas– there is a lot of erosion. So during the Dust Bowl, people found artifacts laying on the surface. But a lot of these have been picked up over the years. So they are getting very, very hard to find now.

IRA FLATOW: Jennifer, I heard that you once tried to get genetic material from a brain that you found in a bog. How did that work out for you?

JENNIFER RAFF: Well, I didn’t find the brain. It was sent to the lab. And this is way back when I was a graduate student. And I was not successful at getting DNA from that brain.

IRA FLATOW: Why? Because– Tell us the– you know, get in the weeds on that.

JENNIFER RAFF: Yes. DNA preservation is very tricky. You’re really lucky in the lab if you get a 50% success rate. So you kind of have to be a special kind of crazy person to really keep working in this field. But–

IRA FLATOW: And you are that kind of person?

JENNIFER RAFF: Yeah, I am, I’m afraid.

IRA FLATOW: That’s good. That’s good.

JENNIFER RAFF: But it– DNA preservation is dependent on not just the age of a sample but also the deposition conditions. So if a sample is deposited in a very dry, cold environment like the Arctic– we like to work up in the Arctic because we get really good preservation up there. And there are some other situations where you’ll get really nice DNA preservation. The type of bone or tissue that you sample from can determine the likelihood of preservation. So there’s just a whole lot that goes into that. And you can’t know, unfortunately, in advance whether or not you’re going to get DNA successfully from something. You have to just try it. And that can be very frustrating sometimes.

IRA FLATOW: Yeah, a brain that gets bogged down is not–

[JENNIFER CHUCKLING]

All right, it’s the last one I promise.

[AUDIENCE BOOING]

There are the BOOS. OK. I asked for them.

[APPLAUSE]

It wouldn’t be my show if I didn’t come up with a few of these every week. Let’s go to the audience right here.

CHILD: How did the Clovis hunt?

IRA FLATOW: Oh, how did the Clovis hunt? The mammal. Animals.

FREDERIC SELLET: I have to say– I have to say–

IRA FLATOW: These kids are asking the greatest questions today.

[LAUGHTER AND APPLAUSE]

That’s great.

[APPLAUSE]

FREDERIC SELLET: You guys are– you guys are asking hard questions. We know they hunt them with those Clovis points I made. We have a mammoth found in Arizona at the Naco site that had about eight Clovis points found. And we think that that mammoth actually ran away and survived. And managed to to run away, so the Clovis hunters never caught up with him. So we know that they were throwing spears into the mammoth, and probably quite a few spears in order to kill it. But they must have still tracked the mammoth for hours– possibly for days– before they could act, they could butcher the animal. So how they hunt them? We don’t really know they hunt them in large groups or individually.

One thing is sure, that mammoths are really, really big. So you have to run really fast if you miss.

[LAUGHTER]

[APPLAUSE]

So–

IRA FLATOW: You’re highly motivated, then. And that must imply also that if you want to increase your odds of killing a mammoth, you don’t hunt singly. You go with a group of people, right? I mean–

FREDERIC SELLET: Correct. What we know is that most people hunt communally. So if you hunt on your own, you are much better off hunting a turtle than a mammoth.

[LAUGHTER]

So some of these groups– we’re talking about groups of maybe a dozen, two to three dozen people. So they would come together in aggregate during the year. And then they would help each other. And, you know, when you have 30 people it’s a little bit easier to go after something big as a mammoth.

IRA FLATOW: I wish we could give the mammoth equal time here to defend themselves. But I’m Ira Flatow. This is Science Friday from PRI, Public Radio International.

[CHEERING AND APPLAUSE]

Let’s go right here, yes.

WOMAN: In the last decade or two, there’s been so much information coming now based on genetics data and using it also in all sorts of sciences. What do you think is the greatest application of genetics in archeology has been discovered? And then what do you think is going to be the great discover– or what would you like to see?

JENNIFER RAFF: So, I think the greatest thing that has happened in genetics recently has been really the ability to get complete genomes from ancient contexts. That has really revolutionized our discipline. Because instead of looking at just one marker of ancestry that’s inherited, say, just from your mother or just from your father– which is what we did before– we’re able now to get complete genomes from ancient remains. And that can tell us about all of a person’s ancestors. And that really helps us understand what a population– what– the events that led to a population’s history. Because population histories and evolution is actually archived in the genomes of the people who lived through those histories, and their descendants. So that has been just absolutely transformational in our discipline. And in new techniques, improved techniques in the lab for getting DNA out of really tricky bones. That’s been really, really helpful.

I think that one of the major things that we have learned from these new types of evidence has been that you can’t assume anything about human history. You can look at archaeological evidence. You can look at other types of evidence. But they don’t necessarily tell you about what a population has done. Artifacts can– that you see, moving around the landscape– may tell you something about how culture is shared between populations or between groups, but that doesn’t necessarily mean that people were moving around themselves, and exchanging mates and having descendants. So we see examples of contact between different cultures through the exchange of artifacts and material goods without there actually being any kind of biological consequence to that. And then we also see the opposite in the archaeological– right, in the genetic record. We see complete population replacements happening with very little archaeological evidence of that. So you just can’t make assumptions about human history and about human biological history without really going out and looking at the DNA itself.

IRA FLATOW: Oh, thank you. Thank you both for taking time to be with us today. Jennifer Raff is a genetic anthropologist. Assistant professor at University of Kansas in Lawrence. Fred Sellet, also an anthropologist that specializes in ancient stone tools, also at the University of Kansas. Thank you both for taking time to be with us. That’s about all the time we have. Our heartfelt thanks to Debra Fraser, Sarah Jane Crespo, John Cyphers, Jordan Kirtley, Beth Golay, and all the wonderful folks at KMUW.

Oh, and let’s get one last round of applause to our amazing musical guest, Shane Marler and Nikki Moddelmog, who will play us off tonight.

[APPLAUSE]

And to Diana Gordon, Barney Byard, Robert “Lucky” Morris, Joshua Gordon, Bailey Vaughan, Madeline Gosland, and everyone here at the Orpheum Theater for making this wonderful evening possible. And to our production partners at the City University of New York. And we can’t forget our Science Friday staff, yeah! Charles Bergquist, Rachel Bouton, Danielle Dana, Brandon Echter, Elah Feder, Jennifer Fenick, Xochitl Garcia, Luke Groskin, Katie Hiler, Christopher Intagliata, Jen Kwok, Alexa Lim, Johanna Mayer, Annie Minoff, Annie Nero, Soshmita Potok, Daniel Peterschmidt, Christian Skotte, Christy Taylor, Lauren Young, Tony Zisa, and Ariel Zych. Thank you all for coming. In Wichita, Kansas, I’m Ira Flatow. Drive safely everybody. Have a good night.

[APPLAUSE]

MAN SINGING: I know you’re down but I’ll

I’ll carry on somehow

I’ll still breathe when you’re not around

If you change mind sometime

You’ll realize we were fine

I’ll be waiting here for you

Maybe I’m just a fool

Maybe I’m just a fool

Maybe I’m just a fool for loving you

Maybe I’m just a fool

Maybe I’m just a fool

Maybe I’m just a fool for loving you

For loving you

Loving you

[BLUES GUITAR MUSIC]

[CHEERING AND APPLAUSE]

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