A re-evaluation of materials left behind by early human settlers is challenging long-held beliefs about the first culture in North America.
The materials were gathered from sites scattered across North America, all the way to Florida. The sites are identified with what scientists call Clovis culture, known for characteristic spearheads and other tools. The hypothesis that Clovis was the first culture in the New World has been around for about five decades, says Michael Waters, a researcher at Texas A & M University.
"It was thought that these were the first people to enter the New World," Waters says, "and that Clovis and their descendents then spread out across North America, and reached the southern tip of South America within about 1,000 years after that."
To check whether this story was indeed accurate, Waters and a colleague, Thomas Stafford, decided to re-examine Clovis materials using new and improved dating methods. They wanted know more precisely the age of Clovis sites. Their results are in this week's issue of Science magazine.
"Lo and behold! When we did this, we found that we could revise the age of Clovis, so that it wasn't quite as old as it was previously thought," Water says.
The earliest signs of Clovis technology turned out to date back a little more than 13,000 years ago, Water says. He says the culture was around for much less time than commonly thought: just 200 years. That means the Clovis were not the ancestors of later tribes.
Most notably, the new dates suggest that Clovis might not have come first.
Archeologists have previously dated other sites from non-Clovis early Americans, from Canada to South America. Some of those now appear to be older than the ones that Waters has re-evaluated. Waters suspects that the simple story traditionally told of a single culture migrating into the Americas — via a frozen land bridge from Asia — is wrong. His hunch is that there were multiple migrations from Asia, both by land and sea.
"Both routes are viable and possible, and we have to start thinking about the peopling in the Americas being such that people could've arrived at different times, and they could've arrived by different ways," Waters says. "The data that we collected, you know, was probably the final nail in the Clovis-first coffin."
Professor Gary Haynes disagrees, saying, "I would have to say that's a bit of an overstatement."
Haynes, of the University of Nevada, Reno, is impressed by the improved dating for Clovis sites. But he says that, in order to draw the conclusion that the Clovis culture wasn't first, you'd need the same level of accuracy in dating early artifacts linked to other cultures.
"They've given us a good, clear picture of Clovis," Haynes says. "But we're still left with this fuzzy picture of all the other stuff they say existed at the time of Clovis — but we don't know that for certain."
Happily, this is one dispute that can be resolved fairly easily, with yet more precise dates of other early archeological sites. Michael Waters at Texas A & M knows he has a few more archeologists to convince, and he'll keep at it.
"It's going to be very exciting to chase after this problem of the peopling of the Americas," Waters says, "and I'm confident that we'll eventually come up with a coherent model that makes sense."