Lost Tribes of the Green Sahara

Sereno, a National Geographic Society explorer-in-residence and one of the world's most prolific dinosaur hunters, had led his first expedition into the Ténéré five years earlier, after negotiating agreements with both the leader of a Tuareg rebel force and the Niger Ministry of Defense, allowing him safe passage to explore its fossil-rich deposits. That initial foray was followed by others, and each time his team emerged from the desert with the remains of exotic species, including Nigersaurus, a 500-toothed plant-eating dinosaur, and Sarcosuchus, an extinct crocodilian the size of a city bus. The 2000 expedition, however, was his most ambitious—three months scouring a 300-mile arc of the Ténéré, ending near Agadez, a medieval caravan town on the western lip of the desert. Already, his team members had excavated 20 tons of dinosaur bones and other prehistoric animals. But six weeks of hard labor in this brutal environment had worn them down. Most had mild cases of dysentery; several had lost so much weight they had to hitch up their trousers as they trudged over the soft sand; and everyone's nerves had been on edge since an encounter with armed bandits.

Mike Hettwer, a photographer accompanying the team, headed off by himself toward a trio of small dunes. He crested the first slope and stared in amazement. The dunes were spilling over with bones. He took a few shots with his digital camera and hurried back to the Land Rovers.

"I found some bones," Hettwer said, when the team had regrouped. "But they're not dinosaurs. They're human."