Where did we come from? Evolutionary biologist Spencer Wells is pretty close to the answer. He’s the National Geographic “Explorer-in-Residence” and heads an initiative called the Genographic Project. His new book is called Pandora’s Seed. By collecting DNA samples from people around the world, he’s tracing the paths of human migration, and he’s uncovered some startling facts about homo sapiens’ early history: we almost didn’t make it.