clipped from: www.sciencedaily.com   
The human race was divided into two separate groups within Africa for as much as half of its existence, says a Tel Aviv University mathematician. Climate change, reduction in populations and harsh conditions may have caused and maintained the separation.
“We wanted to look into the ancient history of our species. How did we live throughout most of our existence as a species?  Did we live as one — or were we fractured into small groups? Until now, it wasn’t really clear,” says Rosset.

Researchers believe that about 60,000 years ago, modern humans started their epic journeys to populate the world. This time period has been the primary focus of anthropological genetic research. However, relatively little is known about the demographic history of our species over the previous 140,000 years in Africa.

The current study returns the focus to Africa and thereby refines the understanding of early modern Homo sapiens history.