Migrating people had 20,000-year campout

By Maggie Fox, Health and Science Editor

WASHINGTON (Reuters) - People who migrated from Asia to the New World camped out for 20,000 years on land now submerged under the Bering Strait between Alaska and Siberia, according to a genetic analysis published on Tuesday.

A team at the University of Florida combined studies of DNA, archeological evidence, climate data and geological data to come up with their new theory, which describes a much longer migration than most other researchers have proposed.

"We sort of went out onto a limb, incorporating all this nongenetic data," molecular anthropologist Connie Mulligan said in a telephone interview.

Mulligan's team proposes that the people who left Central Asia to eventually populate the Americas passed quickly through Siberia, and then got stuck in Beringia -- a former land mass that now lies under the frigid Bering Sea.

There they stayed for 20,000 years, until glaciers melted about 15,000 years ago, opening a route to the Americas.

"The reason there is no archeological evidence for that occupation is that the area is under water," Mulligan said.

The researchers used sequences of mitochondrial DNA taken from Asians and Native Americans for their analysis. This type of DNA is passed along virtually unchanged from mother to child.

The small mutations that occur can be used as a genetic clock to track the descent and the sizes of ancient populations.