The Sahara desert isn't known for its greenery. But there's evidence it was once much lusher than today, dotted with water holes and lakes. Now a study suggests that three massive rivers used to plough through the desert, too—cutting pathways north to the Mediterranean coast.

Researchers used climate models to estimate rainfall more than 100,000 years ago. They found that ancient monsoons formed 400 miles north of where they do today, spilling rain on mountains in the central Sahara. That storm water would have drained north, powering three rivers the size of the Nile, and forming vast wetlands in what is now Libya.

The westernmost river, referred to as the Irharhar, was the most likely path for migrants—and clusters of archaeological sites in Algeria and Tunisia back up that idea. The analysis is in the journal PLoS ONE. [Tom J. Coulthard et al., Were Rivers Flowing across the Sahara During the Last Interglacial? Implications for Human Migration through Africa]

There's no telling whether humans made it to Europe by these routes. But the alternatives were travelling along Africa's west coast, or up the Nile—so these three ancient rivers would have offered a nice shortcut. Now, of course, the waterways are buried beneath the dunes, along with any footprints our ancestors may have left behind.

—Christopher Intagliata

[The above text is a transcript of this podcast.]

