AMERICA'S STONE AGE EXPLORERSPBS Airdate: November 9, 2004Go to the companion Web siteNARRATOR: Stone Age America, 13,000 years ago: A virgin land, a world great beasts have ruled for millions of years, and for early human settlers it is an age in which stone weapons can be the difference between life and death.This is a Clovis spear point. It is the greatest technological breakthrough of the Stone Age and long thought to be the oldest human artifact unearthed in the Americas. For years, these Stone Age weapons of mass destruction were thought to represent a culture of prehistoric big game hunters who came over a land bridge from Asia to become the first Americans. But new clues are forcing scientists to rewrite an epic story that, until now, had been considered the gospel.Can these magnificent Clovis spear points, over 13,000 years old, help solve one of the greatest riddles of North American archaeology? Who were the first Americans and where did they come from? America's Stone Age explorers, up next on NOVA.Major funding for NOVA is provided by the Park Foundation, dedicated to education and quality television.We see you inventing the next big thing. Microsoft is proud to sponsor NOVA for celebrating the potential in us all.Science: it's given us the framework to help make wireless communications clear. Sprint is proud to support NOVA.And by The Corporation for Public Broadcasting, and by contributions to your PBS station from viewers like you. Thank you.NARRATOR: The ancestors of modern humans originated in Africa at least 150,000 years ago. By 40,000 years ago, they had radiated out of Africa and were occupying most of Europe, Asia and Australia. But half the Earth, humans had yet to explore. How people first came to America remains one of the greatest mysteries of our past.PAUL MARTIN (University of Arizona): Archaeologists have been looking for the earliest for a long time. It's been a Holy Grail for them. Who was first?MICHAEL COLLINS (University of Texas): The whole question of the peopling of the Americas is a huge piece of the total human experience. That's just a question we can't leave unanswered.NARRATOR: Who were these earliest explorers? Where did they come from? How did they make this epic journey to the New World?The first clue to the mystery was found in a dried up lake in Clovis, New Mexico. Here, in 1933, archaeologists uncovered a stone tool made by human hands, an ancient spearhead. It became known as the Clovis point.Alongside the Clovis point was the skeleton of a mammoth, which, evidently, the spear point had been used to kill. Later, scientists were able to date the bones, establishing the age of the spearhead as 13,500 years old. It made the Clovis point the oldest human artifact ever found in America. Archaeologists have now discovered thousands of Clovis spear points across much of the continent.MICHAEL COLLINS: There's Clovis in every one of the 48 states in the United States, Mexico, Belize, Costa Rica, in all kinds of environments.NARRATOR: So many spear points, spreading widely across the continent, suggested a rapid expansion of a weapon crucial to the lives of the earliest Stone Age American explorers.KENNETH TANKERSLEY (Northern Kentucky University): The Clovis point was the fundamental basis for survival in Ice Age America.DAVID KILBY (University of New Mexico): Clovis points, arguably, represent the state of the art in hunting weapons on Earth at the time and are probably capable of taking down just about any animal on the late Pleistocene landscape.NARRATOR: In an age defined by its most valuable resource, stone, the Clovis spear point represented a great technological breakthrough, transforming rock into a killing machine.DENNIS STANFORD (Smithsonian Institution): It's a very distinctive type of artifact. As you can see here, it has a flake that's been taken out of the base and there's also a flake on the other side removed from the base, and these are called flutes. And beyond that the projectile point is flaked on both sides. You see it's worked here and it's worked on this side, which is what we call "bifacial."NARRATOR: The bifacial design transforms a rough stone into a projectile with a serrated sharp edge. The fluting, some archaeologists speculate, allows Clovis hunters to rapidly load and reload the deadly blades onto spear shafts.DENNIS STANFORD: And when you throw this at an animal, this goes in and sticks in the animal and this comes back out so you can put a new one on it and start hunting again.DAVID KILBY: There have been some experiments carried out by archaeologists, using replicas of Clovis points and other stone tools, in which they were used to penetrate the hides of modern elephants, elephants which had already deceased. And it's found, in, in all these cases, that they actually are all very efficient weapons and could potentially kill mammoth where you'd get them into the soft, vulnerable underbelly and then quickly back away.NARRATOR: Testimony to the deadliness of the Clovis spear point is that, in a dozen cases, they were discovered in the remains of butchered mammoths. This led scientists to connect the spear point to a catastrophe that befell these Stone Age giants. For around 13,500 years ago, all the mega fauna in the Americas went extinctthe mammoths, the giant armadillo, the giant sloth, the short-faced bearall disappeared within a few hundred years.But who were these big game hunters with their Stone Age weapons of mass destruction? Where did they come from?When archaeologists looked for an answer, they found an important clue in the climate of the ancient world. Between 24- and 13,000 years ago was the last great Ice Age. Huge swaths of the northern hemisphere lay frozen under ice. These giant ice sheets locked up vast quantities of water, causing sea levels to drop far lower than they are today.DAVID MELTZER (Southern Methodist University): When you've got that much ice on land, what happens is that it draws, essentially, water out of the oceans. So with that much ice on land, sea levels worldwide are lowered. By lowering sea levels, you expose the continental shelf between Siberia and Alaska, and that made it possible for people to walk to the Americas.NARRATOR: Asia and North America were essentially one great continent, joined by a land bridge more than a thousand miles wide. But although it was possible to walk from Siberia to Alaska, giant ice sheets barred entrance to the rest of the continent. Then, as the climate warmed at the end of the Ice Age, the glaciers receded, opening up an ice-free corridor through the center of the continent. For the first time, it seemed, the door was open to the virgin landscape of the New World.DAVID MELTZER: As that corridor opens up, that's just about the time when Clovis appears in the lower 48. So it all seemed to work out very, very beautifully in terms of the timing of getting these New World peoples from Asia into the Americas.NARRATOR: The timing of the land bridge, the ice-free corridor and the Clovis dates all seemed to fit together in a simple elegant theory: 13,500 years ago, Clovis people, big game hunters from Asia, armed with their lethal Clovis spear point, walked across the land bridge to the Americas, followed the ice-free corridor down into the lower continent and spread across the land, killing all the great beasts. As ice age glaciers melted, the seas rose, submerging the land bridge. The descendents of the Clovis people, the Native Americans, remained isolated until their first contact with Columbus.The theory became known as Clovis First. It was written into the textbooks and taught for the better part of a century. The Clovis spear point became the icon of the first Americans.Clovis First was such a powerful story that, for years, few archaeologists looked back beyond 13,500 years ago. But then a few did. Jim Adovasio has spent the past 30 years excavating at Meadowcroft, a prehistoric site near Pittsburgh, Pennsylvania. The deeper he dug, the further back he descended in time.JAMES ADOVASIO (Mercyhurst College): On these surfaces that you see before us, we have signs of repeated visits by Native Americans to this site. These discolorations literally represent a moment frozen in time.NARRATOR: Each tag marks ancient fire pits that can be carbon dated, creating a cross section of who lived here and when, stretching back 13,500 years.JAMES ADOVASIO: Just below the surface I'm standing on is where the conventional Clovis First model says that the earliest material should stop, basically, that there ought not to be anything beneath it, no matter how much deeper we dug.NARRATOR: But then, Adovasio did go deeper, below 13,500 years, to a time in the Americas, when no trace of humans should exist, according to the Clovis First theory. He was astounded by what he found.JAMES ADOVASIO: The artifacts simply continued, and we recovered blades like this all the way down to 16,000 B.C.NARRATOR: When he published his findings, he was immediately attacked.JAMES ADOVASIO: The majority of the archaeological community was acutely skeptical, and they invented all kinds of reasons why these dates couldn't possibly be right.NARRATOR: Some claimed that nearby coal deposits had contaminated Adovasio's samples, but he was known to be a meticulous excavator. Eventually, a few other archaeologists began to report evidence questioning the Clovis First theory, and they too were attacked.MICHAEL COLLINS: The best way in the world to get beaten up, professionally, is to claim you have a pre-Clovis site.DENNIS STANFORD: When you dig deeper than Clovis, a lot of people do not report it, because they're worried about the reaction of their colleagues.MICHAEL COLLINS: I've been accused of planting artifacts. People will reject radiocarbon dates just simply because there's not supposed to be any people here at those times, and it just goes on and on and on.NARRATOR: Even faced with evidence to the contrary, Clovis First supporters refused to accept that people could have arrived in America earlier than 13,500 years ago. For, as they pointed out, although it was possible to walk across the land bridge into present day Alaska, ice sheets blocked entry to the rest of the continent until at least that time. As they put it, "If people were coming to the New World before then, how could they get past the ice?"Some archaeologists began to defy the dogma and search for an alternative route down the coast of Alaska.JAMES DIXON (University of Colorado at Boulder): Well, when I was a student, we learned that the entire northwest coast of North America was covered by glacial ice all the way out to the continental shelf, so really, there was no opportunity for plants or animals, much less humans, to exist along that coastline during the last Ice Age.NARRATOR: Today, Jim Dixon and Tim Heaton are finding evidence of abundant plants and animals at a time when the northwest coast was thought to be a lifeless, frozen wasteland.TIM HEATON (University of South Dakota): We just cleaned up this caribou antler I want you to take a look at.NARRATOR: Here, along the coast, the glaciers destroyed most traces of the Ice Age world, but Heaton and Dixon have investigated a rare undisturbed site, deep underground in an ancient bear cave.The cave floor is excavated, inch by inch, from dated layers of soil going back tens of thousands of years.ARCHAEOLOGIST: Thanks.TIM HEATON: I think it's a bone fragment.NARRATOR: This excavation has uncovered a record of caribou, fox and bear bones dating back 50,000 years.TIM HEATON: What this suggests is that bears survived the entire last period of glaciation, and if bears could have survived here, it's certainly clear that humans could have also.JAMES DIXON: We now realize that those early portrayals of this massive continental glacier, all the way out to the ocean really is, is not accurate, and that by, oh, 14- to 16,000 years ago, this ice had retreated sufficiently to create habitat for plants and animals and ice-free areas that could have been used by humans.NARRATOR: Abundant vegetation, temperate coastal climate and bear survival are all evidence of a possible Ice Age route to the Americas along the Alaska coast, by sea. But still no evidence that humans had actually made the voyage down the coast.Then another surprise, from deep in the southern hemisphere, at a place called Monte Verde, this site of human habitation in Chile, 40 miles from the Pacific coast, was claimed to date back earlier than Clovis.In 1997, a group of highly regarded archaeologists went to examine the evidence with their own eyes. They saw weapons, tools and other objects, the result of two decades of excavation. After intensely scrutinizing the dating, they confirmed the artifacts were older than Clovis by over a thousand years.KENNETH TANKERSLEY: It wasn't until Monte Verde that we saw the first unambiguous, unquestionable evidence of people here before Clovis. It allowed us to think that perhaps the initial peopling of the New World was beyond 12-, 13,000 years ago and allowed us to look further.NARRATOR: But even as more archaeologists allowed themselves to consider that Clovis might not have been first, the pillars of the Clovis First theory could not be completely toppled; Clovis First remained the entrenched answer to the question of the peopling of Americas.And so it could have stayed until a remarkable discovery. Doug Wallace takes a different approach to the mystery of the first Americans. Instead of archaeology, he's using DNA to reveal traces of ancient migrations. Stored in his lab are DNA samples of indigenous people collected from all corners of the globe. DNA is the molecule of our genetic endowment expressed in a code of four letters representing four different chemical bases.Every cell in these samples contains DNA. But Wallace studies a specific kind of DNA, not from the nucleus, which is a random mix of genes from both parents, but from the mitochondria, the cell's energy factories outside the nucleus.This kind of DNA is inherited only from the mother and is passed intact from generation to generation as lineages diverge. But at a steady and predictable rate, tiny mutations creep, like spelling mistakes, into specific stretches of DNA. The amount of genetic variation between any two lineages can reveal how far back in time they shared a common ancestor.DOUGLAS WALLACE (University of California, Irvine): So what we've been able to do, using genetic variation and comparing the genetic variation of aboriginal populations from all the major continents of the world, we've literally been able to reconstruct the history of migration.NARRATOR: When Wallace and his team analyzed the mitochondrial DNA of Native Americans, they found four distinctive lineages that he labeled A, B, C and D. All four turned out to share common ancestors back in Siberia and northeast Asia.So far, these findings were consistent with the Clovis First theory that the first Americans came from Asia. But when Wallace calculated how long ago the Asian and Native American DNA diverged, he was shocked. He repeated his work, as did other labs. The results were consistent. Three of the four main ancestral groups A, C and D, diverged from their Asian forbears at least 20,000 years ago. And even more striking, the first Americans didn't all come at once, but in at least three waves of migration.DOUGLAS WALLACE: All of the papers that have been published have come to a very similar conclusion: that the first migration was in the order of 20- to 30,000 years ago.NARRATOR: The DNA results made the Clovis First theory even more unlikely. Together with the evidence from Monte Verde, Meadowcroft and other sites, it now seemed as if Clovis people could not be the first Americans. The Pacific coast route offered a possible alternative to the Bering land bridge and the ice-free corridor, and the DNA suggested that humans had been coming to America in waves and far earlier than ever imagined.Only one last pillar of the epic Clovis First theory was still standing: the artifact that inspired the theory, the icon of Stone Age America, the Clovis spear point itself. Where did it come from?Archaeologist Dennis Stanford decided to search for its origins along the route from Asia to America. But as he worked back from Alaska to Siberia, the trail went cold. The weapons and tools he found in Asia were quite different.DENNIS STANFORD: After looking at the collections, we were disappointed that we didn't find what we thought we would find, and I was surprised to find that the technologies were so much different.NARRATOR: The Clovis spear point is a single stone, bifacial, or shaped on both sides, with a flute, or groove, at its base. The spear points in Asia are made from lots of small razor-like flints called micro-blades embedded in a bone handle.DENNIS STANFORD: Microblade technology is making a projectile point or a knife blade out of bone and then cutting a slot in it and then putting the microblades in the slot. And that's a totally different philosophy, entirely, than using the bifacial projectile point, as you can see here. It's just a total different mindset.NARRATOR: Now there was a real puzzle. The DNA says the earliest Americans are from Asia, yet the Clovis point, is nowhere to be found in Asia. It was a puzzle, not only for Stanford, but also his colleague Bruce Bradley. Bradley is an anthropologist and a skilled flint knapper, an expert at crafting stone tools.One day, while making a Clovis point, he had a moment of inspiration. He remembered a popular science book he had seen when he was a student. It showed pictures of ancient spearheads made by the Solutreans, people who lived in Ice Age France and Spain. Their spear points resembled Clovis points. It seemed unbelievable, but Stanford and Bradley posed the question, "Could the Clovis point and some of the earliest Americans be from Europe?"DENNIS STANFORD: I was going through the old arguments: "Yeah, well, Solutreans... 5,000 years older than Clovis." And "You've got the Atlantic Ocean out there." So I wasn't convinced that we really ought to push forward on it.BRUCE BRADLEY (University of Exeter): I remember it a little bit differently. You said, "Are you out of your mind?"NARRATOR: Despite the unlikelihood of the connection, Stanford and Bradley decided to pursue the idea. Bradley thought an important clue might lie in the specific technique involved in making Clovis points.BRUCE BRADLEY: You can see how this, starting from this side, went and took off this whole other side. This is what we call an overshot or outre passe flake, a very intentional process.NARRATOR: Overshot flaking was an unusual technique that left behind a distinctive byproduct, big flakes, at ancient Clovis stone working sites. Bradley wondered if traces of this technique might show up in southwestern France, where the Solutreans had lived 20,000 years ago.When he went there to investigate, one thing soon became clear: the Solutreans were a remarkable people. The Solutreans were responsible for much of the great Stone Age art of Europe and were the forefathers of the artists who painted the Sistine Chapel of the Ice Age, the Caves of Lascaux.DAVID MELTZER: They did a lot of carving in bone and in antler and in ivory, they fashioned spear throwers, they painted on cave walls; they had a fairly complex means of expressing themselves through their art.NARRATOR: Could these remarkable Stone Age Europeans have brought the Clovis spear point to the Americas?Bradley's research took him to the local museum in the town of Les Eyzies, France. What he saw were hundreds of what looked very much like Clovis points.BRUCE BRADLEY: What we're seeing here is only the finished objects, only the things that museum people thought were really good for display. It doesn't always show you how things were made.NARRATOR: To connect the Solutreans and Clovis, he needed to find out if they produced their spearheads using the same big flake technique.BRUCE BRADLEY: So what we do is we go back to the collections of the broken materials, which is probably 99 percent of what there is here, and in that we're seeing the various ways that the Solutreans were making the things, not just the finished objects. And so it's the pieces that are hidden away that are going to tell us the most.NARRATOR: And there in the drawers were big flakes, a clear sign that the Solutreans had made their spearheads in an identical technique to that of Clovis.BRUCE BRADLEY: This is a good example here that shows a kind of flaking that...where the flake is struck from one side and went across the surface...removed some of the other side. And these pieces show it over and over and over again. I mean just about any piece you pick up shows this very special technique. I just knew there had to be some kind of a connection.NARRATOR: Clovis and Solutrean spear points not only look alike, they are made the same unusual way. To Stanford and Bradley, this was a powerful clue that prehistoric explorers had come from Europe and brought with them the technology that transformed Stone Age America: the Clovis Spear Point.It was an outrageous idea with a few big problems. The Solutrean's culture ended in Europe around 18,000 years ago, and the Clovis point would not arrive in America for another 5,000 years. If the Solutreans brought the Clovis point to America, where had they been?Stanford and Bradley needed to find some artifact in the Americas to bridge the time gap. They scoured Clovis sites across the continent, places where other archaeologists had been digging for years. Then, from a site called Cactus Hill, in Virginia, a possibility, a point that resembled the Solutrean style, and it dated far earlier than the Clovis.DENNIS STANFORD: Here we have a projectile point from a feature that dates right at 15,900 years or 16,000 years ago, which is clearly right in the middle between Clovis and Solutrean. And what's really exciting about it is that the technology here is very similar to Solutrean. In fact it's closer to Solutrean than Clovis where you can see that it's in a progression between Solutrean and Clovis, so you have Solutrean, Cactus Hill and Clovis.NARRATOR: For Stanford and Bradley, the Cactus Hill point bridged the 5,000-year gap, connecting Solutreans in France and Clovis in America. But their fledgling theory now confronted another massive problem almost 3,000 miles wide: the Atlantic Ocean.At the time of the Solutreans, ice sheets stretched down as far as southern France, where winter temperatures were 50 degrees colder than today. Unlike the more temperate Pacific coast, the Atlantic would, at times, have been thick with icebergs and blizzards.LAWRENCE GUY STRAUS (University of New Mexico): There are 5,000 kilometers of open North Atlantic Ice Age conditions to be crossed. There are icebergs floating around in the Bay of Biscay, and it's a polar desert.NARRATOR: Could the Solutreans, a Stone Age people, have made such a voyage?Stanford flew to a place where he thought he might find the answer: Barrow, Alaska, on the edge of the continent at the northern most tip of the United States. Here he hopes the native people of Alaska, the Inupiat, might reveal how, thousands of years ago, the Solutreans could have made an epic transatlantic journey.Today the Inupiat survive temperatures of minus 35 degrees. For warm waterproof clothing, traditionalists prefer caribou skin and sinew, the same materials available to their Stone Age ancestors. And for food on their seasonal hunting trips, the Inupiat turn to an age old resource, the sea.RONALD BROWER (Inupiat Heritage Center): The sea has been our garden. We don't have any growth...growing things. There's nothing growing, up here, so we depend on the sea for our livelihood, and most of our hunting is based on sea mammal hunting. We have the great whales, polar bears, walrus, seals and fish.NARRATOR: Even with warm clothing and food, could the Solutreans have made boats capable of crossing thousands of miles of treacherous, icy water? Today, traditional Inupiat build umiaks, whaling boats, using sealskin and caribou sinew stretched on wood frames and waterproofed with oil applied directly from seal blubber. These same techniques and materials would have been available to prehistoric people.DENNIS STANFORD: Boats like these can...could have made the journey that we're hypothesizing for Solutrean people quite well. In fact, I was noticing on the distance signs here in the middle of town, they say it's about 1,500 miles to Greenland. And we know that, prehistorically, Eskimo peoples moved that distance from here to there several times.NARRATOR: In Arctic seas filled with pack ice conditions similar to the Ice Age Atlantic, the boats pass the test as the Inupiat paddle from ice floe to ice floe.DENNIS STANFORD: Well, it certainly is exactly the way I think the Solutrean guys were dealing with the ice edge, because you can get in and off of the ice real rapidly and, and if the weather gets a little, little nasty then you just pull up off...out of the water and onto the ice.NARRATOR: For Stanford and Bradley, this ability to travel great distances in Arctic conditions suggested how the Solutreans could have made their epic journey during the Ice Age.They had now gathered a broad range of evidence: physical similarities between the Solutrean and Clovis spear points, a similar technique used to make them, and the Cactus Hill point connecting Solutrean and Clovis in time. All added up to a radical and provocative theory, that the Solutreans invented the Clovis point technology, and Ice Age Europeans were amongst America's earliest explorers.Immediately, the theory was attacked. The close resemblance of the spear points was not enough.DAVID MELTZER: You can always find...if you're careful in your selection, you can always find one or two things that look alike. I'm not looking for one or two things. I'm looking for lots of things: the artwork, the antler spear throwers, where are they? Did they get left behind? There's no reason why they shouldn't be there, but we don't see it.NARRATOR: Can one spear point bridge a 5,000 year gap?KENNETH TANKERSLEY: Although Cactus Hill, its radiocarbon date and artifact have been used to bridge the gap between the Solutrean and Clovis, in reality, it will take a lot of sites, a lot of radiocarbon dates and a large assemblage of artifacts to make that connection.NARRATOR: And although the Solutreans may have been capable of making a cross-Atlantic journey, there's little archeological evidence that they did.LAWRENCE GUY STRAUS: There is absolutely no evidence of deep sea fishing. There's absolutely no evidence, for that matter, of boats.NARRATOR: But Stanford argues that crucial evidence is missing, submerged under 300 feet of water as rising sea levels inundated the Solutrean coastline at the end of the Ice Age.The debate raged on, with arguments for and against the Solutrean theory. Then came evidence that, again, seemed like it might end the battle: DNA.It was the latest report from colleagues of Doug Wallace who were investigating early human migrations. They were puzzling over mitochondrial DNA samples from a Native American tribe called the Ojibwa.DOUGLAS WALLACE: When we studied the mitochondrial DNA of the Ojibwa we found, as we had anticipated, the four primary lineagesA, B, C and Dbut there was about a quarter of the mitochondrial DNAs that was not A, B, C and D.NARRATOR: There was a fifth source of DNA of mysterious origin. They called it X, and unlike A, B, C and D, they couldn't find it anywhere in Siberia or eastern Asia. But it was similar to an uncommon lineage in European populations today. At first, they thought it must be the result of interracial breeding within the last 500 years, sometime after Columbus.DOUGLAS WALLACE: We naturally assumed that perhaps there had been European recent mixture with the Ojibwa tribe and that some European women had married into the Ojibwa tribe and contributed their mitochondrial DNAs.NARRATOR: But that assumption proved wrong. When they looked at the amount of variation in the X lineage, it pointed to an origin long before Columbus, in fact, to at least 15,000 years ago. It appeared to be evidence of Ice Age Europeans in America.DOUGLAS WALLACE: Well, what it says is that a mitochondrial lineage that is predominantly found in Europe somehow got to the Great Lakes region of the Americas 14,000 to 15,000 years ago.NARRATOR: Could X be genetic evidence of the Solutreans in America? Further investigation raised another possibility. The ancient X lineage may have existed in Siberia, but died out, though not before coming over to America with Ancient migrations.DOUGLAS WALLACE: And so the DNA data itself cannot distinguish between those two alternatives. It could be either from Europe or from Siberia, of a population that is now lost.NARRATOR: So X could have reached the Americas through Asia, or across the Atlantic directly from Europe. The DNA could not provide a storybook ending.MICHAEL COLLINS: The hypothesis that Clovis may derive from Solutrean, it's going to be...it's going to take years to sort that out. That's, that's not the most important thing right now. The very fact that that hypothesis is being articulated forces us to think in, in much broader terms about the problem of the peopling of the Americas.NARRATOR: With Clovis First in ruins and the Solutrean theory still hotly contested, now archaeologists must pull together their discoveries into an all-encompassing new theory of the peopling of the Americas. And central to that quest is the origin of the Clovis point.KENNETH TANKERSLEY: Although the technology needed to produce a Clovis point was found among other cultures during the Ice Age, the actual Clovis point itself is unique to the Americas, suggesting that it was invented here in the New World.NARRATOR: Perhaps the Clovis spear point was not brought by big game hunters from Asia or seafaring Solutreans from Europe. Could the Clovis point be the first great American invention?A prime place for investigating Clovis culture in America is the Gault Site, in central Texas. Unlike its hot, arid surroundings, Gault is a shady park-like oasis. Michael Collins, from the University of Texas, started excavating at Gault in 1998.MICHAEL COLLINS: As you can see, the Gault site is really a special place. It's well watered, got lush vegetation, an abundance of resources, both plant and animal. It's an ideal place for people who are hunters and gatherers.NARRATOR: Gault is the best of both worlds: nearby is a parched plateau for hunting game, while down in a cool stream-fed valley, are pecans, walnuts and berries. And not far from the streambed is a natural resource so crucial to the survival of prehistoric people that it defines the whole age, stone.MICHAEL COLLINS: We're at an outcropping here, a rich outcropping of cretaceous chert. This was the choice material for making stone tools for at least 13,000 years. It's pretty good stuff when you break it open. It...see how it breaks. You get nice flakes of it out of there.NARRATOR: To a Stone Age craftsman, this particular rock was perfect for fashioning stone tools and may have drawn people for hundreds of miles. To date, nearly half a million Clovis artifacts have been found at Gault, but curiously, very few are spear points.MICHAEL COLLINS: The Clovis spear point is the, sort of the icon of Clovis culture. But what we see at the Gault site is we only have about 30 projectile pointsmostly broken and worn out and discarded Clovis pointsin comparison to the several thousand other tools.NARRATOR: What can explain the lack of spear points at one of Stone Age America's premiere stone quarries? And why would big game hunters need any other tools beside the spear point?At the Texas Archeological Research Lab, Marilyn Shoberg examines the Clovis tools under a microscope. By studying the scratches on the tool she hopes to discover its function. The last hand to use this tool did so some 13,000 years ago.MARILYN SHOBERG (Texas Archeological Research Laboratory): Very fine striations that are running parallel to the edge of the blade and these striations all parallel to the edge, indicate that it was used primarily in a longitudinal motion, sort of slicing, as in slicing grass.NARRATOR: To test her idea, Collins and his colleagues created replica tools, made from the same Gault stone and used them at the site.MICHAEL COLLINS: In cutting just this little bit of grass here I've already developed a bright sheen right along the edge and under the microscope that'll be a very bright polish built up on that edge, and it'll have striations in it going this way, because of my cutting motion.NARRATOR: Under the microscope, the replica tool has the same sheen and pattern as the Clovis tool. Perhaps Clovis people were cutting grass or reeds for baskets, bedding or thatched roofs for shelter.Shoberg examines other types of tools found at the site.MARILYN SHOBERG: Deep troughed grooves, characteristic of contact with bone...NARRATOR: A spear point used for hunting.MARILYN SHOBERG: All along the edge of this artifact there is polish that's characteristic of contact with a soft material, like meat.NARRATOR: A knife used for slicing food.MARILYN SHOBERG: This is the hide punch.NARRATOR: A punch or awl for sewing tailored clothing.MARILYN SHOBERG: This little blade fragment was used to engrave or incise bone.NARRATOR: Small pieces of limestone have been discovered at Gault, etched with mysterious geometric patterns among the only examples of Ice Age art in America. Art, tailored clothes, baskets and thatched roofs for shelter: all contradict the old Clovis First image of nomadic, mammoth murderers. And although the remains of a mammoth were found at Gault, Collins and colleagues have found far more bones of turtles, birds and small mammals. This menu suggests more variety than a big game hunter's diet of wooly mammoth and bison.MICHAEL COLLINS: What emerges from the totality of all that information is these people were generalized hunters and gatherers. They were living on a variety of animals, staying in one place for quite a while and not simply pursuing large game as their primary way of life.NARRATOR: There's even evidence of trade networks between Clovis people at different sites across the continent. It's not uncommon to find Clovis points hundreds of miles from the source of the original rock. And different bands of Clovis people probably traded more than just tools; they may have been exchanging potential spouses.DAVID KILBY: Although we tend to think, sometimes, of hunter gatherers as being fairly simple in adaptation, it's actually a pretty complicated world in which they live. There have to be social mechanisms in place that allow you to sort of share information and relate to surrounding groups in some systematic way and to be on good enough terms with them that you're able to, sort of, exchange mates, and therefore genetic viability, across an otherwise, sort of, sparsely populated landscape.NARRATOR: A clue that Clovis people had intimate knowledge of the landscape lies, once again, with the Clovis point. Many have been found in caches, bundles of spear points, hidden away for later use by Clovis hunters.David Kilby has traveled the United States and studied all of the nearly two dozen known caches.DAVID KILBY: This strategy of caching suggests intimate familiarity with the landscape and sort of a complex understanding of the distribution of different resources around the landscape. The fact that they're putting tools and raw material in specific places on the landscape and leaving them behind, suggests that they knew with some confidence where they were going to be in the future.NARRATOR: Caching, trade and travel must have involved patterns of seasonal migration developed over dozens of generations. This emerging picture of the Clovis lifestyle contradicts the old image of Clovis as a single people, nomadic big game hunters, sweeping rapidly across the continent with their lethal spear, wiping out all the great beasts.MICHAEL COLLINS: The longstanding notion of the rapid spread, the archaeologically rapid spread, of Clovis across the continent, has been taken to mean the spread of a people across the continent. An alternative to that might be that the spread of Clovis is actually the expansion of a technology across existing populations, a little bit analogous to the fact you can go anywhere in the world and find people driving John Deere tractors. Technology can spread across different languages, different cultures, quite readily.NARRATOR: Perhaps this is the birth of an intriguing new theory for the peopling of America: the first Stone Age explorers arrive on this continent more than 20,000 years ago, much earlier than scientists ever imagined. They come from Asia, and maybe even Europe, by land and by sea. Tenuously, at first, these different groups spread across the virgin land, and over thousands of years they develop an intimate knowledge of the New World. Around 13,500 years ago, a stone weapon is invented, so powerful, so crucial to survival that it spreads swiftly across all the people of the Americas. With this new technology they take root, proliferate and prosper. Clovis is the first great invention of the New World and the icon of the peoples who may rightfully be called the first Americans.