Seattle Hold the potty humor, please, but archaeologists digging in a dusty cave in Oregon have unearthed fossilized feces that appear to be the oldest biological evidence of humans in North America.
The ancient poop dates back 14,300 years. If the results hold up, that means the continent was populated more than 1,000 years before the so-called Clovis culture, long believed to be the first Americans.
"This adds to a growing body of evidence that the human presence in the Americas predates Clovis," said Michael Waters, an anthropologist at Texas A&M University who was not involved in the project.
DNA analysis of the dried excrement shows the people who lived in the caves were closely related to modern American Indians. Their genetic roots reach across the Bering Strait to Siberia and eastern Asia.
"These are probably the ancestors of some of the Native Americans living in America now," said Eske Willerslev, director of the Centre for Ancient Genetics at the University of Copenhagen. He co-authored the report that appeared in Thursday's online Science Express.
The age of the finding also calls into question the theory that people who crossed the Bering Land Bridge to Alaska migrated south through ice-free corridors as glaciers began to break up. Geological evidence suggests the corridors weren't open 14,300 years ago, though the glaciers had pulled back from the coasts.
"People probably came either by boat or maybe even walking along the West Coast," Willerslev said.
The Americas were the last continents populated by humans, and scientists have long believed that the Clovis people were the first to arrive in what are now Canada and the United States. They brought with them their distinctively fluted stone spear points and tools.
A recent reanalysis of Clovis artifacts pinpointed the era's beginning at about 13,000 years ago.
Before the Oregon discovery, the oldest human remains in North America were two sets of bones about 13,000 years old from California and Nevada. Kennewick Man, the skeleton found on the banks of the Columbia River in Eastern Washington, dates to 9,400 years ago.
Dennis Jenkins, a University of Oregon archaeologist led the recent cave excavations.
Jenkins and his students uncovered hundreds of coprolites, as fossil dung is called in polite scientific society, at Paisley Caves, about 220 miles southeast of Portland as the crow flies. Dry weather preserved the poop, which was sheltered from rain and tucked into corners apparently used as latrines.
"They look just like Fido's droppings in the backyard," he said.