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 Ice age human melting pot infographic
Graphic shows likely routes out of Africa and timeline of human evolution.


Ice age human melting pot

By Duncan Mil

March 15, 2012 - Research suggests that as modern humans migrated out of Africa, ice-age conditions forced them to shelter in “refugia” occupied by smaller groups of distant cousins. Subsequent evolutionary change may have led to one global species of human – and the demise of its Neanderthal and Denisovan ancestors.

By about 20,000 years ago, modern humans had made their way out of Africa and replaced their distant cousins -- the more primitive populations of humans -- living in Europe and Asia. However, until now, the details of this transition have been sketchy.

A new study by John Stewart of Bournemouth Universtity and Chris Stringer of the Natural History Museum in London is painting a clearer picture of the way in which modern humans took over from their ancient ancestors, such as the Neanderthals and Denisovans, in Eurasia.

The authors compiled genomic data on these two ancient human populations and coupled them with studies of other organisms that persisted over many glacial cycles. They then used that information to create new models of the massive human migration from Africa, which began approximately 100,000 years ago.

These models suggest that “refugia”, or locations that harbour relict populations of a once-widespread species, were important in determining the pace and pattern of this modern human takeover. Their models demonstrate how a refuge in a particular part of the world can lead species to important evolutionary changes, including the creation of new species altogether. The research appears in the March 16, 2012 issue of Science.

PUBLISHED: 15/03/2012; STORY: Graphic News; PICTURES: Getty Images, Darren Curnoe, José-Manuel Benito Álvarez