Radiocarbon dating stone tools
Some 15,500 years ago early nomadic North Americans had already set up camp near Buttermilk Creek in central Texas's hill country, where they left behind impressive array of stone tools and artifacts.
Such an old habitation predates the widespread toolmaking tradition known as Clovis, which spread across the continent some 12,800 to 13,100 years ago and was once thought to mark the first wave of settlers in the Americas.
But, as Waters pointed out, known tools from that period in Siberia and northeastern Asia are relatively scant.
Given the previous finds in Wisconsin, Chile and other sites, John Shea, an associate professor of anthropology at Stony Brook University in New York State, notes that "it's been pretty clear" that humans were living in the Americas long before the Clovis tradition emerged.
And although early studies arrived at some pretty errant dates, the technology has been refined and now, Bamforth notes, "it really works." But because the technology has only come into wide use in the past several years, many sites discovered and described earlier did not have the benefit of OLS dating.
So if no biological material was available for handy radiocarbon dating, researchers would have had no way to gauge exactly when an assemblage of tools was made.
"There are a lot of problems with the Clovis-first model," Waters said, adding that it is "time to abandon [it] once and for all." Some of the pre-Clovis tools found at the Buttermilk Creek site, such as "bladelets," do show similarities with bifacial (two-sided) techniques found in Asia, suggesting a deeper history."Artifacts move around in the ground all the time," Bamforth said.But, he noted, the researchers behind the new work "have shown in great detail that the site is intact," adding that he was impressed with "how carefully they were able to document the age." The team found "uniform particle size distribution" in the clay around the fragments, suggesting that it had not been disturbed when—or since—the rock pieces were dropped, Nordt explained during Wednesday's briefing.Likewise, Bamforth was not surprised by the discovery of the new evidence."I think it's kind of been waiting to be found," he says of a substantial pre-Clovis site.