Hunting For Traces Of America's First Inhabitants
IRA FLATOW, host:
This is SCIENCE FRIDAY. I'm Ira Flatow.
When and how did humans first arrive in the Americas? For years, scientists have thought the first travelers arrived here at the end of the last ice age, somewhere around 13,000 years ago. And they got here by wandering over a land bridge from Siberia to Alaska.
And archaeologists have found distinctive spear points from the same period at sites all over the Americas. They're called Clovis points, after the town of Clovis, New Mexico, where they were first discovered.
But now a new discovery of stone chippings and blades has some scientists rethinking when the settlers first set foot in the Americas because this new cache of stone tools from Texas predates the Clovis period by thousands of years, suggesting that people were here as long ago as 15,000 years ago. That's about 2,500 years earlier than we thought.
How did those earlier people get here? Can we really be sure these newly discovered artifacts are from the same earlier time? How accurate is that dating?
Joining me now to talk about the research is one of the authors of a study that's out in this week's journal Science. Michael B. Collins is director of the Gault Archaeological Project. He's also a research professor of anthropology at Texas State University in San Marcos.
Welcome back to SCIENCE FRIDAY, Dr. Collins.
Dr. MICHAEL B. COLLINS (Director, Gault Archaeological Project; Texas State University): Well, it's good to be back with you, Ira. It's been a while.
FLATOW: Yes, it has. And I see you've been very busy.
Dr. COLLINS: I've been busy, I have indeed.
FLATOW: Tell us what kind of artifacts, first, that you found there -lots of them.
Dr. COLLINS: Yes, quite a number of them. And the number is large because most of the pieces are small. But they are distinctive. They are clearly man-made. They are the chippings from making and refurbishing stone tools. And one stone tool can produce 300, 400 or more chips.
So not surprisingly, the (unintelligible) has produced many more chips than it has finished tools. And in fact, the finished tools are few in number, and most of those are worn out and damaged. So they're not a full representation of what the stone tool industry of that time and place looked like.
FLATOW: If our listeners would like to join in on the conversation, our number is 1-800-989-8255. And you can leave us a message, or you can tweet us, @scifri, @-S-C-I-F-R-I. Or join the discussion on our Facebook page, /scifri.
How significant is this finding, and how sure are you of how old they are?
Dr. COLLINS: Well, let me turn your question around a little bit and say that we're very confident in this particular effort of dating an older-than-Clovis site. The nature treated us well. We do not have preserved materials suitable for radio-carbon dating. So we're relying on an alternative technique that's less widely used called optically stimulated luminescence dating and OSL for short.
OSL dating depends on high-quality samples, and that's true in most sciences, isn't it? That the better the samples you start with the better results you're going to have at the end.
And the quality of the quartz grains that we use is excellent. So our dating is good. And our OSL dates are in nice, well-stratified geologic deposits. There is a stack of cultural materials from about 1,000 years old going, as you go deeper, they go back in time to 13,000. Those are all known, recognized cultures.
Our OSL dates line up with the known ages of those cultures. So when we look at the dates, 13,000 to 15,000-plus, underlying Clovis, and we have artifacts down there, we have a good deal of confidence in that. And that is what makes this particular site of high importance.
FLATOW: How much luck is involved here?
Dr. COLLINS: A good deal of luck but there's also a good deal of just plain hard research that goes into locating a site like this, knowing what to do with it when you get there and then excavating, analyzing, studying and reporting it.
FLATOW: And let's talk about that a bit because you have to have some sort of luck in finding the right site. But I'm sure there's a lot of research that goes into it.
Dr. COLLINS: That's right.
FLATOW: But why do you go deeper, where some other scientists might have stopped?
Dr. COLLINS: Well, we're working against an inertia, two inertias, really, that one has said for very many years that Clovis was the oldest culture in the Americas, at around 13,000 to 13,200 or 13,300 years ago. And some people haven't gotten over that, in spite of the fact for the last nearly 20 years we have had quite a few sites with strong indications of people being here before Clovis.
And another thing - and that's improving. More and more people are accepting the concept or are at least willing to investigate it.
The other thing, the other inertia that we have, and it's also improving rapidly and greatly: American archaeology has - grew up in the social sciences.
And not long ago, the vast majority of practicing archeologists in this country had very little background in the earth sciences and consequently didn't really think about the fact that okay, I have found cultural material here, I'm backing this excavation to Clovis, so that's the oldest culture, I'll just quit here, without thinking: You know, the dirt below that is just a little bit older. Why don't I look at that and see what's in it? There just wasn't that - that mindset was not particularly common. But happily, both of those things are changing for the better.
FLATOW: There's a hypothesis that the first Americans may have crossed over around 16,000 years ago not from the familiar Siberian land bridge that we've heard about but from Europe. How does that hypothesis come about, and is there any evidence to support it? And how do you cross the Atlantic Ocean?
(Soundbite of laughter)
Dr. COLLINS: Well, those are huge questions. And it's a bold hypothesis that has been around for a while, but it's currently being formulated and talked about and not enjoying a whole lot of acceptance.
But if you look at the archaeological, the earliest archaeological materials that we know from the western side of the Western Hemisphere, all down the west side of North America and South America, there is a technology, a way of making stone tools that really has an Asian flavor to it.
And it probably fits with genetic and other evidence that much of the ancestry of the Americas derived out of Siberia, biologically and technologically.
On the other side of the continent, some of the earliest archaeological evidence that we have actually has a - and this includes Clovis - has a technological signature very similar to the Solutrean culture of primarily France and Spain that dates between about 21,000 and 16,000 years ago.
Those - that technology is so similar that it's awfully hard to imagine it having sprung up independently in two different places. So then you have the question of: How do you bring a culture across the North Atlantic?
Well: A, we know that if anyone got to the Americas before about 13,500 years ago, they almost certainly had to come by boat because the entire span of Canada, from the Pacific to the Atlantic, was under an ice sheet. So people had to have come around that. If they came down the Pacific Coast, they're bound to have used boats along - probably along the near shore.
We know that people in Japan were plying the waters of the Pacific by 33,000 years ago in boats. We know that people arrived on the Solomon Islands and Australia by 50-or-so-thousand years ago. That had to have involved watercraft of some kind. So boat technology has a great time depth in human technological history.
The nature of the waters of the North Atlantic and the North Pacific is such that they support one of the most enormous biotas in the world. The numbers of fish, sea mammals, seabirds and even land mammals - if you want to include the polar bear - those food masses make the Serengeti Plain look like a desert.
FLATOW: Yet you say this theory is not very well accepted?
Dr. COLLINS: That's true, but - and it's because nobody has very thoroughly and systemically put together all the various lines of evidence. That's about to change later this year. Dennis Stanford of the Smithsonian Institution and Bruce Bradley of Exeter University in England have a book that's in the final stages of editing at the University of California Press putting together the oceanographic, archaeological, ethnographic evidence that really tightens up that hypothesis. And they simply presented it as a hypothesis, but I find it a very compelling one.
FLATOW: 1-800-989-8255. It is a really interesting theory. Let's see if we can get a phone call or two in. Chris in Michigan.
CHRIS (Caller): Hi.
FLATOW: Hi, there.
Chris: Thank you for taking my call.
CHRIS: Most of my question's already been addressed, but it was that -first, I want to commend you for publishing this information. It's extremely courageous, considering the environment you're doing it in. My question was why Clovis points have never been found in Siberia, but yet Solutrean - which you already addressed - points in the Iberian Peninsula and Southern Europe are virtually indistinguishable. My second question would be: Have you read "First American" by Chris Hardaker? And I would get off the air. Thank you.
FLATOW: Okay. Thank you.
Dr. COLLINS: I'm aware of Chris Hardaker's work, but I haven't read it. So I will sidestep that part of the question. The - I think the reason we don't find Clovis in Siberia is that it never was there, that this was a different tradition of tool-making. It shows up in east -northeastern Asia, and all the way down from Alaska to southern Chile and into the interior of the Americas quite some distance. I believe that that is a trip of - a movement of technology out of northeastern Asia and down the western side of the Western Hemisphere.
Dr. COLLINS: It could involve both.
FLATOW: We're talking about Clovis this hour on SCIENCE FRIDAY, from NPR. We're talking with Michael Collins.
One tweet came in: Why is it the first artifacts were found in New Mexico? It seems like an unlikely area, as opposed to coasts.
Dr. COLLINS: Well, by the time of Clovis, I think people have been here quite a number of thousand years. The Freidkin site certainly suggests that. The Monte Verde site in Chile suggests that, one to 2,000 years older than Clovis.
So by then, people had spread from the coastal margins, all across the interior of the Americas. And the earliest discoveries of Clovis almost exclusively were at places where Clovis points were associated with skeletons of mammoths. And mammoths are very big animals, and they're very big bones. And people would spot these in gravel quarries or in erosional gullies and so forth and so on. And they would attract their attention, and they get poking around, and they would find artifacts associated with those bones.
FLATOW: The artifacts that you've uncovered that you say are thousands of years older than Clovis, when you look at them, are there any signs on them that might point to a coming of Clovis later?
Dr. COLLINS: That's a debatable question. I sort of lean toward the fact that most of the Freidkin artifacts don't suggest a continuity with Clovis. But the - professor Waters and his research group at Texas A&M feel like there are more similarities, and that they may have an antecedent to Clovis represented there. Well, this will be a debate that'll go on for some time, I'm sure.
FLATOW: And I'm sure the debate's going to get thicker as you talk about that theory of coming over from North America - from Europe to North America.
Dr. COLLINS: Absolutely. That'll add another dimension to it. I mean, that's one already controversial...
(Soundbite of laughter)
Dr. COLLINS: ...and it's hardly - it's just barely been presented in print at this point.
FLATOW: And you, what are you going to be up to next?
Dr. COLLINS: Well, I'm working on a site just literally 300 meters from the Freidkin site. That's the Gault site. It is an enormous Clovis site - the largest, the most prolific Clovis site in the Western Hemisphere. I've been working on it for 20 years. We're nearing the end of our fieldwork and beginning to do the analysis. And before long, we'll be producing a definitive monograph on that site.
FLATOW: Can you give us a hint...
Dr. COLLINS: And it, too...
FLATOW: ...a little preview?
Dr. COLLINS: It, too, has stuff older than Clovis that we've found and not yet reported.
FLATOW: So it's got all this stuff there, also. Yeah. And we'll wait for you to come back and talk about it, because it looks like we - as you say, we are opening up the debate one more time.
Dr. COLLINS: Yes, we are. And it will continue. You know, Ira, this is the most exciting time to be in one of the most exciting research fields imaginable. It changes every day.
FLATOW: And you just hate your job, then?
Dr. COLLINS: I hate my job.
(Soundbite of laughter)
Dr. COLLINS: Just like you hate yours.
(Soundbite of laughter)
Dr. COLLINS: It shows, doesn't it?
FLATOW: It certainly does. Well, enjoy - you have to enjoy yourself and your work, right?
Dr. COLLINS: Yes, you do.
FLATOW: Well, good luck to you, and thank you for taking time out of your busy work schedule to come and talk with us today.
Dr. COLLINS: I thoroughly enjoyed it, and the best to you, Ira.
FLATOW: Thank you. We'll talk to you later. We're waiting for that new monograph to come out, and we'll talk to you when it comes out.
Dr. COLLINS: Good.
FLATOW: Have a good weekend.
Michael B. Collins is director of the Gault Archaeological Project. He's also a research professor at - of anthropology at Texas State University in San Marcos.
We're going to take a break. And when we come back, we're going to talk about drilling down deep toward the Earth's mantle. Just what is a mantle? It's not a sports figure in this case. We'll talk about it later after this break. Stay with us.
(Soundbite of music)
FLATOW: I'm Ira Flatow. This is SCIENCE FRIDAY, from NPR.
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