Consider the ancient human fossils from a Moroccan cave called Jebel Irhoud, which were described just last year. These 315,000-year-old bones are the oldest known fossils of Homo sapiens. They not only pushed back the proposed dawn of our species, but they added northwest Africa to the list of possible origin sites. They also had an odd combination of features, combining the flat faces of modern humans with the elongated skulls of ancient species like Homo erectus. From the front, they could have passed for us; from the side, they would have stood out. Fossils from all over Africa have...