And let that be a lesson to you

A New York Times article on a dig in the Sahara that's turned up skeletons of ancient man, but also evidence that climate is a variable thing: "For most of the last 70,000, the Sahara has been a desert. About 12,000 years ago, a shift in the winds moved the monsoon rains to the north, and parts of the desert turned green, including the Gobero site in Niger where Dr. Sereno discovered some 200 graves. About 4,500 years ago, the winds shifted again, rain stopped falling, the desert returned and the people left."