WASHINGTON (Reuters) - DNA from ancient human feces found in a cave in Oregon provides biological verification that people were in North America 14,000 years ago, researchers said on Thursday.
By Maggie Fox, Health and Science Editor
WASHINGTON (Reuters) - DNA from ancient human feces found in a cave in Oregon provides biological verification that people were in North America 14,000 years ago, researchers said on Thursday.
The findings, published in the journal Science, add to growing evidence that people were living in the Americas earlier than the once widely accepted date of 13,000 years ago, based on bones from the so-called Clovis culture in the southwestern United States.
"The dates of the coprolites are more than 1,000 years earlier than currently accepted dates for the Clovis-complex," the researchers wrote.
!ADVERTISEMENT!Dennis Jenkins, a senior archaeologist at the University of Oregon, found the dried-out samples in caves known as the Paisley Caves, about 220 miles southeast of Eugene, Oregon, on the eastern side of the Cascade mountain range.
In with the dried-out samples of excrement, known as coprolites, are sinew and plant fiber threads, hide, basketry, cords, rope, wooden pegs and animal bones.
Jenkins got an international team of experts to sample and date the excrement. Two different teams carbon-dated the feces, and others examined the DNA in them.
"The Paisley Cave material represents, to the best of my knowledge, the oldest human DNA obtained from the Americas," said Eske Willerslev, director of the Centre for Ancient Genetics at Denmark's University of Copenhagen, who helped analyze the DNA.
"This is actually, in our view, the first well-supported evidence humans were there," her colleague Thomas Gilbert agreed in a telephone interview. "We have got enough information to say they are from native Americans."
INTERPRETING EVIDENCE
The issue of when humans first arrived in the Americas is contentious. Most experts agree they migrated from Siberia over a land bridge that once existed in what is now the Bering Strait between Alaska and Russia.
The best evidence is from the Clovis culture.
"At Clovis there are human remains everywhere. There are either human remains or there are stone tools," said Gilbert.
"Before Clovis, there's almost nothing. There are things like a bone that has got cut marks on it and if you want to believe that humans were there you say a knife made it and if you want to believe humans weren't there you say it came from the bite from a lion."
One archeological site in Monte Verde, Chile, may date as far back as 33,000 years ago, and in 2004, Dr. Albert Goodyear of the University of South Carolina said carbon dating of apparently burnt plant remains found in his state showed they may be as old as 50,000 years -- a very controversial finding.
Genetic and linguistic studies tend to put the date of the migration at about 15,000 years ago, which fits in with evidence of when glaciers would have receded and cleared the strait for people to pass. Other genetic studies of modern Native Americans suggests their DNA lineage dates to about 15,000 years ago.
"Not only have we got native American DNA, we have got it right at the beginning of the groups," Gilbert said.
Gilbert said with more and better DNA samples they may be able to date the mitochondrial DNA -- inherited directly from the mother -- of whoever left them in the cave.
Some of the coprolites contain DNA from foxes, wolves or coyotes. Gilbert says it is possible the people ate such animals, or that some of the coprolites came from animals that ate human or human remains.
"Whether the human ate the dog or the dog ate the human, it doesn't matter," he said.
(Reporting by Maggie Fox, editing by Will Dunham and Jackie Frank)
