There is a petroglyph panel in northern Wyoming has been reliably dated by archaeologists to about 12,400 years before the present. This makes it a very early record of human habitation in the American West.
And not long ago, you could have said that it was among the very earliest records of people living in the Rockies. For about 60 years, researchers have believed that humans known as the Clovis peoples migrated from Asia via the Bering land bridge and settled in North America, gradually working their way down into South America, incidentally driving the Pleistocene giants like the mammoth and mastodon to extinction along the way.
But this week researchers have published new carbon dates of Clovis sites that indicate that the Clovis cultures arrived about 11,050 years ago and survived only until about 10,900 years before the present. These new dates, which overturn wisdom about the peopling of America accepted since 1950, means that humans very likely inhabited the continent long before the Clovis.
This in turn means that the family trees of today’s Indian tribes will have to be rewritten. Clovis peoples probably were not the progenitors of all later Native Americans, as previous research has long maintained. It may also mean that the verdict of “not guilty” can be returned on the charge against the Clovis of killing off the Pleistocene giants.
Some Native Americans claim that they have “always” inhabited the continent, an idea that conflicts with the available evidence. But this new evidence helps to push back the dates of habitation much further, getting a little closer to always.
Texas A&M University anthropologist Michael Waters and Thomas Stafford of Lafayette, Colorado’s Stafford Research Laboratories used very precise carbon-14 dating of Clovis sites to determine when they were occupied. The refined technology allows dating of the sites to within 30 years plus or minus, compared with a margin of error of 250 years using older techniques.
“I think this paper does basically provide the final nail in the ‘Clovis first’ coffin,” Waters said in an interview.
Previous hypotheses have had the Clovis peoples crossing the Bering land bridge into Alaska, then gradually peopling the Americas as far as Tierra del Fuego in South America over a few millennia.
But the Waters and Stafford work shows that there simply wasn’t enough time to traverse and colonize that much territory. That means that some other people must have been prior to the Clovis, perhaps as long ago as 25,000 years before the present. These earlier people could have come via the Bering land bridge, or by sea, on routes that hugged the islands and shores of Asia and Alaska as much as possible. At the time, this route would have had many sea mammals that could have provided food.
“With this new data we shown that the Clovis time period is only about 200 years, a maximum of 20 human generations. If people were coming into a new continent, into a strange land,” Waters says. “They would have had to adapt to the hardwood and coniferous forests, to the grasslands and deserts. Every place had different plants and animals they would have had to learn to exploit. You have to find the materials to survive.”
But instead the Clovis peoples apparently settled into the North American landscape. “They knew how to exploit these environments quite effectively.”
Clovis is often referred to as a culture, but in fact it is characterized primarily by its technology. They used stone, bone and ivory to make tools, including the famous Clovis point for hunting with spear and atlatl, as well as other tools like scrapers for cleaning hides, punches, and adzes for chopping wood. They also used ivory from mammoths and mastodons to make projectile points.
Most of the known Clovis sites are in the Rockies, especially in Montana, Wyoming, Arizona and Colorado. “It’s a very distinctive technology,” Waters says, “We only find it in the 48 contiguous U.S. states and sometimes in Mexico.” But once about 100 miles south of the current U.S.-Mexico border, Clovis technology virtually disappears.
Modern genetic research indicates that the first people to come to the two Americas originated in northeast Asia about 25,000 to 20,000 years ago. Most genetic studies are converging on a homeland near the border of Russian and Mongolia or Russia and China. They either came before the last glacial maximum (about 20,000 years ago), or they came after the glaciers began to recede, about 13,500 years ago. In between the two periods, ice two miles thick covered the northern hemisphere as far south as the Great Lakes and the Tetons, making travel difficult, at least.
But it seems likely now that people were on the continent prior to 13,500 years ago. At the Mud Lake site in Wisconsin, there is evidence of human butchering of mammoth remains. There is strong evidence from a site called Cactus Hill in Virginia that people were living there 16,000 years ago.
Some researchers believe that the improved hunting technology introduced by the Clovis peoples resulted in the extinction of the large Pleistocene mammals that had previously inhabited North and South America. In addition to mammoths and mastodons, there were giant beavers, giant sloths, and the famous saber-toothed tiger. The end of the proboscidians can be dated fairly precisely, at around 11,000 to 10,900 years before the present.
But says Waters, “Most of the Pleistocene mammals may have been extinct before Clovis ever shows up. There were dwindling herds of mammoth and mastodon … Clearly Clovis were hunting these animals, but it’s not a blitzkrieg of extinction.”
After the Clovis arrived, the climate in North America changed dramatically, getting cold again, then warming into the climate regime we live in today. The Clovis people adapted to those changes. On the plains, where game was abundant, they became the Folsom people.
“We need to stop thinking of the peopling of the Americas a single event, along with the ruling paradigm of the ‘Clovis first’ model,” Waters says.
“It is highly improbable that within 200 to 350 calendar years, people entered North America; adapted to biomes ranging from artic tundra to grasslands, deserts, and rainforests; increased in population; and reached the southern tip of South America within the span of 10 to 18 human generations. This suggests that human populations already existed in the New World before Clovis.”
The Waters and Stafford work was published in the journal Science of February 23, 2007.