Science Story

02 December 2008 23:38 BST

Fossilised excrement oldest evidence of North Americans

Fossilised excrement from over 14,000 years ago is the oldest evidence of humans in North America, scientists claim today.

The fossils were found in the Paisley caves in Oregon and the discovery is said to support the idea that Native Americans were living in North America at least 1,000 years before the Clovis culture.

An international team of scientists carbon dated the excrement to 14,300 years ago.

Writing for the Science Express website today, they argue that the fossils provide evidence of apparent genetic ties to Siberia or Asia.

The faeces contain two main genetic types of Asian origin that are unique to present day Native Americans.

The researchers say this is proof that Native Americans are descendants of the first immigrants to the continent and that immigration took place approximately 1,000 years earlier than otherwise believed.

The 'ice-free corridor theory' says that people from Siberia migrated across the land bridge that once connected Siberia and North America.

From there, they continued south and spread out across the American continent.

This migration is estimated to have occurred about 14,000 years ago when a corridor opened up in the giant glacier that covered the American continent.

But the fossilised excrement challenges this, the researchers say.

"Our findings show that there were people south of the ice cap several hundred years before the ice-free corridor developed," said Professor Eske Willerslev from the University of Copenhagen.

"The first humans either had to walk or sail along the American west coast to get around the ice cap.

"That is, unless they arrived so long before the last ice age that the land passage wasn't yet blocked by ice."