Arrowheads and DNA from ancient feces dating back 13,200 years from the Paisley Caves in Oregon provide insight into the ancient culture of what is now the United States.

The findings are believed to be from around the time of the Clovis culture, the University of Oregon reported. The study results are based on 190 radiocarbon dates of "artifacts, coprolites, bones and sagebrush" extracted from the stratified layers of the caves.

The radiocarbon dating suggests the artifacts are even older than Clovis times, and suggest two point-production technologies may have overlapped and even developed separately. The Clovis culture may have sprung up in the Southeastern U.S. and spread west, while Western Stemmed traditions started in the east and moved west.

"From our dating, it appears to be impossible to derive Western Stemmed points from a proto- Clovis tradition," said lead researcher Dennis L. Jenkins of the University of Oregon's Museum of Natural and Cultural History. "It suggests that we may have here in the Western United States a tradition that is at least as old as Clovis, and quite possibly older. We seem to have two different traditions co-existing in the United States that did not blend for a period of hundreds of years."

DNA cannot directly undergo radiocarbon dating, but researchers washed potentially contaminating carbon out of the ancient fecal matter (coprolites) with distilled water, allowing them to radiocarbon date the digested fibers. The findings suggest the human coprolites were of Siberia-east Asian origins and are between 13,000 and 13,200 years old.

"Through replicating data we were able to confirm the authenticity of what is the oldest direct evidence for humans in the Americas," said co-author Michael "Michi" Hofreiter, a biologist in DNA laboratory of the University of York in the United Kingdom. "The results of this study are exciting, because they show that the hypothesis that the Clovis people were the first Native Americans, which has been the prevailing idea for the last decades, is wrong. Now researchers need to come up with a new model for the settling of the Americas."

The findings were published July 7 in the journal Science.