Ancient Rivers in Sahara Desert Supported Human Migration Routes to Mediterranean

First Posted: Sep 12, 2013 08:13 AM EDT

The Sahara desert is known for its blistering hot and dry conditions. In fact, the Sahara is the world's hottest desert and the third largest after Antarctica and the Arctic. Covering most of North Africa, it stretches from the Red Sea to the outskirts of the Atlantic Ocean. Yet this massive desert wasn't always so hot and dry. It turns out that about 100,000 years ago, three ancient river systems may have created viable routes for human migration across the Sahara to the Mediterranean region.

The three river systems are no longer on the surface of the desert. Instead, they're largely buried by dune systems. Yet when these rivers flowed in North Africa between 130,000 and 100,000 years ago, it's likely that they provided fertile habitats for animals and vegetation. In fact, they probably created "green corridors" across the region that animals and humans could travel through.

"It's exciting to think that 100,00 years ago there were three huge rivers forcing their way across a 1,000 km of the Sahara desert to the Mediterranean--and that our ancestors could have walked alongside them," said Tom Coulthard, one of the researchers, in a news release.

In fact, the rivers that the researchers discovered were massive in their scope. At least one of them is estimated to have been about 50 miles wide and largely perennial. The most likely migration route for humans was a river known as the Irharhar, which is the westernmost of the three identified.

The idea of human migration along these rivers isn't all that farfetched. Previous studies have shown that people have travelled across the Saharan mountains toward more fertile Mediterranean regions. Yet how they accomplished this feat has been a source of speculation. There are many ways that this migration could have occurred, including single trans-Saharan migration, many migrations along one route or multiple migrations.

Now, though, the existence of these ancient rivers may reveal exactly what path our ancient ancestors took. If the rivers existed as green corridors, it's likely people could have travelled along them toward the Mediterranean.

Currently, the scientists are planning on investigating the probability that these routes were used for migration. In addition, they aim to learn exactly how much water the rivers contained, which could allow them to better assess how viable these rivers would have been as green corridors.

The findings are published in the journal PLOS One.

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