Modern humans are the only surviving hominin from what was once a rich, fairly bushy family tree. But why did we alone survive? We may never have a definitive answer to that question—but we shouldn’t be too quick to underestimate the intelligence of our ancestors, says anthropologist Ian Tattersall, author of The Strange Case of the Rickety Cossack and Other Cautionary Tales From Human Evolution. (Read an excerpt.)

His book details the efforts of anthropologists to untangle our messy human lineage, based solely on the subtle differences in the skeletons of our forebears. And it documents anthropologists’ evolving theories about our human origins, as well as some of their most spectacular mistakes, such as the characterization of an early Neanderthal fossil as a Cossack horseman afflicted with rickets so severe, he furrowed his brow into a permanent expression of pain.