Clue to early Americans lies in origin of the feces

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 Native Americans. 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 appears 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.

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.

Willerslev acknowledged that working with feces lacks the cachet of studies on skulls or spear tips. He and his collaborators say their subject matter drew jokesters like flies are drawn to ... well, you know.

"I've heard it all," said Dennis Jenkins, the University of Oregon archaeologist who led the excavations. "My colleagues call me Dr. Poop."

A trove of diet, genetic information

But coprolites, as fossil dung is called in polite scientific society, can be a trove of information on diet and genetics.

Jenkins and his students uncovered hundreds of coprolites in their six years of work 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.

In fact, Jenkins wasn't sure at first the feces came from humans.

He was curious, though, and eager to cooperate when he heard Willerslev was looking for possible sources of ancient American DNA.

The Danish DNA expert said his own interest in the subject was sparked by a boyhood fascination with Sitting Bull and other American Indians.

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 re-analysis of Clovis artifacts pinpointed the era's beginning at about 13,000 years ago.

But several other archaeological discoveries have raised doubts about the "Clovis first" theory, including evidence of human settlement 15,000 years ago in Chile. Stone tools and mammoth bones with butchering marks from two sites in Wisconsin date to more than 14,000 years ago. Artifacts from a rock shelter in Pennsylvania have dated back 18,000 years.

But none of those sites, all of which are controversial, offered up human remains — even in the form of poop.

"That's what Paisley Caves provides," Waters said. "Solid evidence of a human presence."

Traces of animal DNA

Not everyone is convinced.

Of six coprolites from Oregon identified as human by DNA and protein analysis, three dated to around 14,000 years. The team collected DNA from all 67 people who might have come in contact with the feces, to rule out the possibility of contamination with modern genetic material.

But the scientists also found traces of DNA from foxes, wolves or coyotes in some of the samples.

The most likely explanation is that the early humans ate the animals, or that animal urine got mixed with the feces, Jenkins said.

Anthropologist Gary Haynes, of the University of Nevada, Reno, said it could have happened the other way around: Animal feces were mixed with human DNA. He also points out that several artifacts were dug up in the Oregon caves, including string made from sinew and plant and obsidian flakes, but all are much younger than the oldest coprolites.

"That's kind of a red flag," Haynes said. "Where are the things the people left behind?"

Jenkins and his students plan to keep digging at the caves to try to answer that question.

Now a treeless expanse, the basin where the caves and rock shelters are located was watered by streams and held a large lake 14,000 years ago, Jenkins said. Long-extinct species of camels, horses and bison roamed the scrub and grasslands.

Jenkins has already collected another 24 coprolites from about 8 feet below the surface. That's where the oldest poop came from, and he's hoping for more.

He's also thinking about coprolites collected long before DNA analysis was possible, and the secrets they might yield.

"There are thousands of them," he said, "just sitting on museum shelves."

Sandi Doughton: 206-464-2491 or sdoughton@seattletimes.com