In the spring of 2005 Sereno contacted Elena Garcea, an archaeologist at the University of Cassino, in Italy, inviting her to accompany him on a return to the site. Garcea had spent three decades working digs along the Nile in Sudan and in the mountains of the Libyan Desert, and was well acquainted with the ancient peoples of the Sahara. But she had never heard of Paul Sereno. His claim to have found so many skeletons in one place seemed far-fetched, given that no other Neolithic cemetery contained more than a dozen or so. Some archaeologists would later be skeptical; one sniped that he was just a "moonlighting paleontologist." But Garcea was too intrigued to dismiss him as an interloper. She agreed to join him.
"I was impressed that he hadn't just ignored the burials and continued looking for dinosaurs," she told me.
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.
Garcea explained that the Kiffian were a fishing-based culture and lived during the earliest wet period, between 10,000 and 8,000 years ago. She held a Kiffian sherd next to a Tenerian one. "What is so amazing is that the people who made these two pots lived more than a thousand years apart."