Were ancient human migrations two-way streets?

The worldwide spread of ancient humans has long been depicted as flowing out of Africa, but tantalizing new evidence suggests it may have been a two-way street.

A long-studied archaeological site in a mountainous region between Europe and Asia was occupied by early humans as long as 1.85 million years ago, much earlier than the previous estimate of 1.7 million years ago, researchers report in Tuesday's edition of Proceedings of the National Academy of Sciences.

Early human Homo erectus is known to have occupied the site at Dmanisi later. Discovering stone tools and materials from a much earlier date raises the possibility that Homo erectus evolved in Eurasia and might have migrated back to Africa, the researchers said - though much study is needed to confirm that idea.

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