Saturday, March 26, 2011

Texas discovery pushes back human tool making to 15,000 years ago

A recent discovery 0f 56 stone tools four feet underground in central Texas has proven what archaeologists have suspected for some time now-that humans were on the American continent making tools 15,000 years ago. That date is about 2,000 years before the appearance of the so-called "Clovis culture," whose distinctive fluted and notched arrowheads are the earliest widely found human artifacts in North America.

Evidence for "pre-Clovis" human activity has been accumulating for decades as archaeologists have found a few unusually old sites in places as far apart as coastal Chile and central Pennsylvania. But there were always problems - a jumbling of deposits, uncertainties of dating - that made some archaeologists doubt the age of those discoveries.

The Texas finds, reported Thursday in the journal Science, are likely to persuade nearly everyone. The undisturbed condition of the site, a distinct layer of artifact-containing sediment below the Clovis deposits and dating that consistently puts that layer at 13,200 to 15,500 years old is what makes this discovery especially convincing.

The artifacts were discovered northwest of Austin, an area which has been under excavation for years.They consist of relatively crude scrapers, knife blades, broken and half-repaired spear points, and more than 15,000 flakes and chips testifying to human workmanship. They bear some similarity to Clovis tools, although not a clear one.