Lost Tribes of the Green Sahara

For much of the past 70,000 years, the Sahara has closely resembled the desert it is today. Some 12,000 years ago, however, a wobble in the Earth's axis and other factors caused Africa's seasonal monsoons to shift slightly north, bringing new rains to an area nearly the size of the contiguous United States. Lush watersheds stretched across the Sahara, from Egypt to Mauritania, drawing animal life and eventually people.

Archaeologists have inventoried the stone tools used by these early inhabitants and the patterns inscribed on their ceramics. They have also identified thousands of their rock engravings, which depict herds of ostriches, giraffes, and elephants. Some of the images suggest that along the way the people of the Green Sahara learned to domesticate cattle. But they remain veiled in mystery. Did they arrive here from the Mediterranean coast, central African jungles, or Nile Valley? Were they nomads, or did they stake out territories and build settlements? Did they trade with each other and intermarry, or did they wage war, or both? As the monsoons began to recede, how did they cope with a drying landscape? The only part of the story that then seems clear is that by some 3,500 years ago the desert had returned. The people vanished.