Lost Tribes of the Green Sahara

They arrived at the site six months later. Clad in a salt-stained T-shirt and jeans, Sereno, vibrating with energy, powered up the first of the three dunes, identifying animal bones with nearly every stride—giraffe vertebra … hippo ulna … gazelle humerus. Garcea, a petite woman in unwrinkled chinos and a tennis hat, followed at a more measured pace, bending at the waist to scrutinize each item.

At the top, they surveyed a macabre scene. Around them lay dozens of human skeletons in various degrees of completeness, far more than Garcea had seen at all her other digs combined. Nonetheless, she seemed more interested in what looked to me like tiny gray chunks of gravel. "They're potsherds," she said, and held up one inscribed with a pointillistic pattern. She identified the markings as belonging to a people known to scholars as the Tenerian, a nomadic herding culture that lived during the latter part of the Green Sahara era, 6,500 to 4,500 years ago. Then she picked up another piece. She studied it for a moment, looking perplexed. Instead of little dots, this sherd was decorated with wavy lines. She picked up another like it, then another. "These are Kiffian," she said, her voice rising with excitement.