GRANTS PASS, Ore. -- Stone tools and human DNA from ancient caves in Oregon offer new evidence of how some of the first Americans spread through the continent: Quite apart from the better-known Clovis culture, a separate group occupied the West.
Archaeologists said Thursday that using multiple techniques, they have dated broken obsidian spear points from Paisley Caves to about 13,200 years ago, as old as much different stone tools from the Clovis culture found in the southeast and interior United States. Radio-carbon dating of human DNA from coprolites – ancient desiccated human feces – shows people lived in the caves as early as 14,300 years ago.
The dates indicate that the Clovis style of chipping stone was not the mother of Stone Age technology, as others have theorized, and that the two styles were developed independently by different groups, said Dennis Jenkins, an archaeologist with the University of Oregon's Museum of Natural and Cultural History who led the excavations. That development may have happened in the Ice Age region of Beringia, where Siberia and Alaska were linked, before the two groups migrated south, he said.
The findings by an international team of scientists from the U.S., Britain and Denmark were reported online Thursday in the journal Science.
The Clovis culture is named for elegantly chipped stone points found at a site uncovered in 1929 near Clovis, N.M. The bases are distinctly concave where they were tied to the wooden shafts of spears or throwing darts for hunting. The style found in Oregon is known as western stemmed projectile points, for their thick bases and their discovery throughout the western U.S.
"The big `aha!' here, or the primary significance of this is that ... we have demonstrated that these western stemmed tradition points are the same age as Clovis," Jenkins said in a teleconference with reporters. "There is no evidence of Clovis or any precursor to Clovis in the caves currently, and so that suggests that you've got here, at the exact same time, at least two technologies."
Until now, most western stemmed projectiles with accurate dating have been younger than Clovis artifacts, leading to theories the two technologies evolved from a single source. The new evidence directly goes against that idea. Jenkins said it appears more likely they evolved independently.
Jenkins said the findings suggest those groups of people may have taken separate routes after crossing the Ice Age land bridge from Asia. Those making western stemmed projectiles may have gone down the coast, while the Clovis people traveled through an ice-free corridor in the interior U.S.
But not all experts are convinced.
David Meltzer, professor of prehistory at Southern Methodist University, said the study clearly showed western stemmed projectiles existed at the same time as Clovis. And he said it put to rest any doubts about whether earlier findings of human DNA at Paisley Caves were contaminated by contact with the modern people excavating the site. But he was not ready to say that the stone points showed separate ancient migrations of people through the continent.
"Points are not people," he said. "Just because two ways of fashioning projectile points are different doesn't mean different populations any more than different groups of people drive Hummers rather than Priuses."
Jenkins and others reported in 2008 that they found coprolites in the Paisley Caves that dated back 14,300 years, the oldest radio-carbon-dated human DNA in North America. The DNA was genetically linked to people from Asia as well as modern Indians.
The caves are a string of shallow depressions washed out of an ancient lava flow by the waves of a lake that comes and goes with the changing climate near the town of Paisley, Ore. The caves have been excavated since the 1930s by archaeologists and looted by artifact hunters.
Jenkins and his team went back the past three summers and dug more, this time outfitted in the special suits, respirators and rubber gloves used by high-tech factory workers to assure they did not contaminate anything. They confirmed the dates through radio-carbon dating of the coprolites, bones and plants and through their placement in the layers of dirt built up over the millennia.