DNA extracted from fossilised faeces found in an Oregon cave has provided the oldest unambiguous evidence for a human presence in the Americas.

Genetic tests on the dried excrement, or coprolites, have proved them to be of human origin, while radiocarbon dating has established that they are between 14,000 and 14,300 years old, placing them earlier than any other confirmed human archaeological site in the New World.

The discoveries, from the Paisley Caves on the US Pacific coast, shed important new light on the controversial issue of how and when Homo sapiens came to populate the Americas.

They show that ancient humans were living in North America at least 1,000 years before the “Clovis culture”, named after the New Mexico town where characteristic fluted stone spearpoints made by humans were first discovered in the 1930s.

The Clovis culture, which dates to about 12,900 years ago, is known from across North America from the presence of similar distinctive spearheads. Its people were long considered to be the first Americans, descended from small groups who migrated from Siberia across the Bering Strait.

The “Clovis first” model of colonisation, however, has recently been questioned by the discovery of several human sites that appear to predate this culture. The most notable is at Monte Verde in Chile, where stone implements that show few technological similarities with Clovis tools have been dated to 13,800 years ago.

The new evidence from the 14 coprolites found at the Paisley Caves puts humans in the Americas at an older date than either site. Details of the research are published today in the journal Science.

“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 the University of Copenhagen in Denmark, who led the research. “Other pre-Clovis sites have been claimed, but no human DNA has been obtained, mostly because no human organic material had been recovered.”

Dennis Jenkins, of the University of Oregon, whose field expeditions first discovered the Paisley coprolites, said: “If our DNA evidence and radiocarbon dating hold up on additional coprolites that are now undergoing testing at multiple labs, then we have broken the Clovis sound barrier, if you will.

“If you are looking for the first people in North America, you are going to have to step back more than 1,000 years beyond Clovis to find them.”

The new genetic evidence also offers strong support for the theory that they first reached the continent from Siberia.

The scientists tested the coprolites for mitochondrial DNA, which is always inherited in the maternal line, and which can be used to investigate people's geographical origin. They found that this genetic material belonged to “haplogroups” known as A2 and B2, which are most common among modern Siberians and East Asians.

Dr Jenkins said that this fits with standard explanations of humans' migration to the Americas, though it is impossible to categorise these early Americans' racial group.

“All we're doing in this paper is identifying the haplogroups. We are not saying that these people were of a particular ethnic group. At this point, we know they most likely came from Siberia or Eastern Asia.”

The Paisley Caves, which are on a lake 220 miles southeast of the Oregon town of Eugene, have also yielded many other artefacts of human manufacture from the pre-Clovis era, including threads made from plant fibres and animal sinews that are thinner than the cotton threads which are used to sew buttons onto shirts today.

“To find these threads was just incredible,” Dr Jenkins said. “We found a little pit in the bottom of a cave. It was full of camel, horse and mountain sheep bones, and in there we found a human coprolite. We radiocarbon-dated the camel and mountain sheep bones, as well as the coprolite, to 14,300 years ago.”

Other artefacts from the site include baskets, cords, ropes, wooden pegs and projectile points, though it has not been possible to link these to the Clovis culture.

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