The first, led by the Centre for GeoGenetics at the University of Copenhagen and published in Science, found there was only one initial migration, no more than 23,000 years ago.

This ancestral pool split into two main branches about 13,000 years ago, coinciding with glacier melt and the opening of routes into the North American interior, researchers found.

These became the groups which anthropologists refer to as Amerindians (American Indians) and Athabascans (a native Alaskan people). Previous research had suggested that Amerindian and Athabascan ancestors had crossed the strait independently.