Until now, evidence for the human occupation of North America before the Clovis big-game hunters about 13,000 years ago, has been controversial. Now a major new excavation in Texas has uncovered thousands of stone tools and worked stones from a pre-Clovis layer dating from 13,200 to 15,500 years ago.
"It's time to abandon once and for all the Clovis model and develop a new model for the peopling of the Americas," says archaeologist Michael Waters, a professor at Texas A&M University and lead author of the current study. This new excavation, he says, "takes us a long way along that trail."
The Clovis-first Model
For nearly eighty years the Clovis-First model dominated American archaeology. Supporters believe that the Clovis hunters, whose elegantly fluted projectile points appear across North America were the first people to populate the Americas. They are thought to have crossed the Bering land bridge around 13,100 years ago, and to have made their way into the Americas through an ice-free corridor between the two great ice sheets that covered much of North America.
Over the decades, dozens of sites have been found with evidence of human habitation dating thousands of years before Clovis. However, supporters of the Clovis-first theory have found ways to cast doubt on most of those earlier finds.
The Buttermilk Creek Complex
Waters and his colleagues spent several years excavating the Debra L. Friedkin Site not far from Austin, Texas. They found an undisturbed sequence of occupations from relatively recent Prehistoric levels through Early Archaic, Paleoindian, Folsom and Clovis layers. "Buttermilk Creek was a place people came back to continually, for more than 15,000 years," says Waters.
Under the Clovis layer, the researchers found a 20 centimeter (8 inch) thick layer of clay from which they removed more than 15,000 artifacts. Most of these are pieces of chert, a silica-rich rock suitable for making tools, that were worked or resulted from deliberate chipping or flaking. Among these were 56 blades, choppers and scrapers. Microscopic studies showed that many had been used on hard substances such as bone, or on softer materials such as hides.
"These are the type of tools you would have if you you were a mobile hunter-gatherer," says Waters.
Because there was not enough organic material for radiocarbon dating, the team had to rely on optically stimulated luminescence, or OSL. This technique determines age from the number of charges that have accumulated over time from the absorption of radiation. Two separate sets of measurements produced a perfect sequence of dates from 8000 to 16,000 years ago.
Tom Dillehay, an anthropologist at Vanderbilt University, in Nashville Tennessee, says that the new study adds more evidence to what he and many of his colleagues already accepted, that ". . . the Clovis first theory is dead."
Waters agrees. "Now we can look at those other sites and see how they all fit together."
Reference: "The Buttermilk Creek Complex and the Origins of Clovis at the Debra L. Friedkin Site, Texas," Science, 25 March 2011, p. 1599
Robert Adler - Robert Adler is a science and technology reporter and book author. He divides his time between Santa Rosa, California and Oaxaca, ...
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