‘Green corridors’ led early humans out of Africa

11 September 2013

Early humans migrated through Africa along fertile river systems which once flowed across the Sahara; new research from the University of Hull suggests.

Rivers in Africa

Above: Rivers in Africa, courtesy PLOS ONE.

Although it is widely accepted that modern humans (Homo sapiens) evolved in Africa around 200,000 years ago, the route taken as they travelled northwards towards Europe and South Asia remains a controversial subject.

For the first time, a team of researchers from the University of Hull have been able to use a state-of-the-art computer modelling system to reconstruct ancient rivers and past flood events that would have strongly influenced the migratory routes of early humans. The results show that around 125,000 years ago, three rivers that have now dried up and are buried by dune-systems would have linked mountains in central Africa to the Mediterranean.

Tom Coulthard, Professor of Physical Geography at the University of Hull and lead author of the research paper, explained why these rivers were likely to be crucial to the movement of early humans:

“The rivers would have provided fertile corridors, a 1000km long and up to 100km wide, which ran north across the Sahara, towards the Mediterranean.
 
“In particular, our simulations have identified one river that appears to be the most likely route for human migration. The Irharhar river linked mountain areas experiencing monsoonal climates to temperate Mediterranean environments where food and resources would have been abundant.

“Moreover, the high number of Middle Stone Age archaeological sites that are concentrated around this region provide further evidence that this river was especially important.”

The period of interest to the researchers happened before the last ice age, when there was a dramatic increase in humidity in what is now the Sahara Desert. For some time, this change in climate is thought to have played a significant role in allowing early humans to migrate out of Africa. However, this is the first strong, quantitative evidence for the of presence three major river systems that would have provided suitable routes for the dispersal of early humans.

The full research paper is published today in the journal PLOS ONE.

Although there is considerable evidence to show that humans migrated across Africa as long as 125,000 years ago, the fate of those early migrants is less well understood. Recent research suggests that the ancestors of all humans living today left Africa between 62,000 and 95,000 years ago.

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