"This is almost like a baseball bat to the side of the head to the archaeological community to wake up," he said.Uprooting the Clovis-first model Extracting and describing these thousands of small stone tools has been slow going.The find is "unequivocal proof for pre-Clovis occupation of America," said Steven Forman, of the Department of Earth and Environmental Sciences at the University of Illinois at Chicago.The area where the tools were found, northwest of Austin, must have been an appealing campsite for millennia, because it bears a record of nearly continuous occupation from 15,500 years ago.This arrival would have placed the initial migration from northeastern Asia over the Bering Land Bridge and through the Arctic corridor that opened between ice sheets at some 15,000 years ago.This latest tool evidence, however, suggests that people were already making and discarding stone tools about 15,500 years ago, which would mean that the migration likely occurred even earlier.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.
The technique is "not as precise as radiocarbon by a long shot," Bamforth says."You'd have to get to central Texas, and that would probably take a little while," Waters said.Waters argues that their find of 15,528 artifacts (made from chert, a flint-like rock), which span the 2,400 years before the accepted emergence of Clovis technology 13,100 years ago, is the nail in coffin of the theory that Clovis toolmakers were the first inhabitants of the New World, the so-called Clovis-first model."This was a mobile tool kit—something that was easily transported," Waters said.The prevalence of Clovis style tools—epitomized by fine, fluted (grooved) stone points—across the continent had suggested to many archaeologists for decades that the groups who made these tools must have comprised the first wave of settlement in the Americas.