In addition to the coprolites, Jenkins also found manufactured threads of sinew and plant fibers, hides, basketry, cordage, rope, wooden pegs, animal bones and a couple of projectile point fragments -- but not enough to link the cave's inhabitants to the Clovis people or any others.
The small number of artifacts in the cave suggests that whoever occupied it did so only for a short period, rather than using it as a long-term residence, Jenkins said.
Organic material from the coprolites was radiocarbon dated, and the oldest ones were found to be 14,300 years old.
Willerslev's lab analyzed mitochondrial DNA from the coprolites and concluded that it was similar to DNA from both Native Americans and the populations of Siberia and East Asia.
Fearing contamination of the samples, Willerslev also analyzed samples from all 55 people who visited the cave during the excavations, as well as from all 12 members of his laboratory and showed that none of them had similar DNA.
The coprolites also contained DNA similar to that of the red fox, coyote or wolf. Jenkins said the added DNA could have come from human ingestion of the animals or from the animals urinating on the feces.
Critics, such as anthropologist Gary Haynes of the University of Nevada, Reno, argued that the coprolites could be animal feces and that the human DNA was deposited when humans urinated on them much later.
But Jenkins said that the coprolites also contained human proteins in concentrations too high to have come from urine, as well as human hair.
"Whether the coprolites are human or canine is irrelevant, since for a canine to swallow human hair people had to be present in that environment," he told Science. "Anyway you cut the poop, people and dogs would have had to be at the site within days of each other 14,000 years ago."
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thomas.maugh@latimes.com
