New clue on Americas' oldest humans

WASHINGTON - Scientists have found and dated the oldest human remains ever uncovered in the Americas - a discovery that places people genetically similar to Native Americans in Oregon more than 14,000 years ago.

Working with radiocarbon dating and DNA analysis, an international team concluded that fossilized feces found five feet below the surface of an arid cave are almost 1,000 years older than any previous human remains unearthed in the Americas.

The samples were discovered close to a crude dart or spear tip chiseled from obsidian, as well as bones of horses and camels that were then common in the region. The researchers described their finding as a "smoking gun" in the long-running debate over when and where humans first inhabited the New World.

"What's so exciting here is that we have cells from real people, their DNA, rather than samples of their work or technologies," said Dennis Jenkins of the University of Oregon, Eugene, who oversaw the cave-site dig. "And we have them on the Oregon landscape 1,000 years before what used to be the earliest samples of human remains in the Americas."

The discovery, published yesterday in the online edition of the journal Science, is a blow to the widely held theory that the Clovis culture - named after a site in New Mexico where its distinct artifacts and fluted spearheads were first identified in the 1930s - was the first human presence in North America.

Jenkins said that while the human DNA found in Oregon could be from ancestors of the Clovis culture, none of the distinctive Clovis-era technology has been found there.

The "Clovis-first" theory has been challenged by almost a decade of discoveries from Canada to the bottom of South America that indicate humans were present before the time of the Clovis civilization, about 13,000 years ago.

The theory, generally accepted since the 1950s, was first challenged by discoveries at a site in Western Pennsylvania in 1973. But those findings remain murky.

Yesterday's report is key because it is the first to involve datable human DNA.

The discovery, however, is not without its critics. The cave has been excavated in the past, leading some to wonder whether the newly found samples were contaminated and mixed with other material. In addition, some of the fossilized feces, called coprolites, contain canine DNA.

If the discovery is ultimately confirmed and accepted by anthropologists, it will challenge the prevailing theory about how humans spread across the Americas.

Most experts agree that the first American inhabitants traveled across what was then a land and ice bridge across the Bering Straits from Siberia to Alaska, most likely before 15,000 years ago.

But much of Canada was covered by an ice sheet, and researchers believe the earliest inhabitants would have migrated southward to the high plains of the U.S. along a corridor of ice-free land that opened in inland Canada between 13,000 and 12,000 years ago. Humans then would have spread quickly across North, then South America - doing so in hundreds, rather than thousands of years.

If very early humans lived in Oregon, that suggests they either came directly from Asia by boat or traveled down the Pacific coastline after crossing the land bridge.