Ancient Rivers Across Sahara Could Have Led Humans Out of Africa

Three ancient river systems located in the Sahara could have provided the viable routes that led humans out of Africa, a paper published in the journal PLOS One argues.

By simulating regional paleoclimates, the researchers discovered quantitative evidence of three major river systems that likely existed in North Africa between 130,000 and 100,000 years ago, but currently lay buried beneath the desert's dune systems.

These rivers would have provided "green corridors" across the region, the researchers explain, with one river system estimated to have been 100 kilometers wide and largely perennial. In addition to rivers, the researchers' simulations predicted massive lagoons and wetlands in northeast Libya, some of which may have spanned an area of 70,000 square kilometers.

The westernmost river, called the Irharhar, may represent the most likely route of all, the scientists argue. Corroborating this hypothesis is the discovery of stone tools along the Irharhar River that date back to this period, LiveScience reported.

However, not everyone is convinced.

Chris Stringer, an anthropologist at the Natural History Museum in London, argues that the river systems described in the new study are located too far west to represent a plausible route for migration.

"Even these river systems are some way from the route through the narrow area east of the Nile, which is going to lead them into Israel," Stringer told LiveScience.

Still, the study has its defendants.

"We know that orbital changes affect the monsoon and precipitation in this region," Paul Myers, an earth scientist at the University of Alberta in Canada, told LiveScience. "It has also been shown before that in other periods the Sahara has been quite wet."

About the study, Coulthard said: "It's exciting to think that 100,000 years ago there were three huge rivers forcing their way across 1,000 km of the Sahara desert to the Mediterranean -- and that our ancestors could have walked alongside them."