The Origin of Humankind by Richard Leakey (Basic Books, 1996; reissued 2008, part of the Science Masters series) is a concise synthesis of paleoanthropology written by one of the leading figures in human origins research. Leakey presents his personal view of how Homo sapiens emerged, emphasizing the evolutionary significance of upright walking. He argues that once apes began to walk on two legs, the development of modern humans became possible—and perhaps inevitable.