Ancient feces found in Oregon caves are proof humans inhabited North America more than 1,000 years earlier than previously thought, a discovery that may change theories on how the continent was populated, researchers said.
The findings from Oregon's Paisley Caves contained DNA and were dated 12,300 B.C., according to a paper on the findings published today in the journal Science. That evidence predates the Clovis people and challenges the theory that they were the first North Americans, said Dennis Jenkins, a University of Oregon archaeologist and the paper's lead author.
Spearheads were also found in the newer excavation of the caves, and researchers say those tools -- called Western Stemmed projectile points - show that the caves' inhabitants developed independently of the Clovis. The tools, along with the DNA from the coprolites, or feces, also suggest that the Clovis weren't the founding peoples of the Americas, researchers said.
"I believe that everything we've got indicates that we do have pre-Clovis human coprolites in the Paisley caves," Jenkins said in a telephone interview. "It's beyond reasonable doubt that we have pre-Clovis DNA."
Today's paper describes a second analysis of Paisley Caves findings, after initial results were disputed in 2008 by other archaeologists. Those scientists challenged the results, saying water could have carried newer DNA into older sediment and that excavators might have contaminated evidence with their own DNA.
Paul Goldberg and Francesco Berna, both archaeologists from Boston University who contested the original results, hadn't read the findings as of today and said they couldn't comment on the validity of the results.
Jenkins and his group returned to the caves, gathered new samples, tested them at several independent labs and checked rodent pellets found nearby for human DNA contamination, which would have suggested leaching. Though samples were handled bare- handed last time, this time collectors wore full body suits. The results remained similar.
Tools similar to those discovered in the Oregon caves have been found elsewhere, though they were a development on Clovis technology, said Eske Willerslev, director of the Centre of Excellence in GeoGenetics at the University of Copenhagen and an author on the study. Using radiocarbon dating, the researchers were now able to show that the Paisley spearheads are concurrent with the oldest Clovis points, though slightly newer than the oldest feces.
"It suggests that there was not one, but two, early societies in America," Willerslev said in a phone interview. "Western stem has been known in America for a long time, but everybody thought that it was much younger."
Based on their shape and sharpness, Jenkins said he believes the points could have been used to hunt big game, including mastodons and woolly mammoth. He said researchers found elephant-family proteins on other stones in the caves that he believes were used as tools.
The idea that Paisley Cave inhabitants developed separately from the Clovis, whose oldest U.S. sites are in Montana, South Dakota and Florida, might support a theory of multiple migrations into the Americas, Jenkins said.
The people might have been seafarers who followed kelp 'forests' rich with marine life and surrounded by calm seas from Asia to enter western North America, he said, while Clovis may have migrated from a Siberian land bridge.
"It certainly implies, to me at least, that the coastal migration theory should be taken very seriously," he said.
DNA analysis suggests that the people were Asian and genetically resemble modern Native Americans, and further analysis of more hard-to-extract core DNA may show what contemporary people they are related to, Willerslev said.
Further feces analysis may have bearing on modern medicine, he said. Bacteria that lived in the feces, or 'gut flora,' provide clues to a person's diet and state of health, he said. That means analysis could show what a human's gut flora would look like in the absence of processed foods.
"It's super important to people's health," he said. "It would put out a base."
The Paisley Cave findings are the oldest human remnants discovered in the Americas, Willerslev said, though he said scientists believe that a site with human artifacts in Mount Verde, Chile, comes from approximately the same date.
"I believe that we are going to find older sites, and I say that because if we have people in the Paisley caves who seem to be well adapted to their environment," Jenkins said. "What we find in the poop suggests that they knew their environment very well and they had been in their area for some time."
Evidence that people immigrated to North America by sea may solve questions about the Chile settlement, Jenkins said. Because Chile is so far South, scientists have questioned how they could be the earliest found remains of a people believed to have migrated from Siberia.
"It raises its stock, if you will, another notch at least," he said.