Simon and Schuster, $16.95. Donald Johanson is the paleoanthropologist who discovered in Ethiopia the partial skeleton of a very small-brained creature that walked like a man well over 3 million years ago. Since this particular creature was female, she is known as Lucy, and her appearance has caused excitement and controversy among her finder’s colleagues and rivals. And rivals they are, for paleoanthropologists are as ferocious as any other breed in defense of individual turf—turf, in their case, being theories on human evolution backed by the age of particular fossils, preferably those discovered in person. The uncommitted reader may wonder if it seriously matters whether our ancestors developed larger brains because they walked on two feet, or walked on two feet because they had developed larger brains. By sketching his distinguished and often eccentric predecessors, describing finds and search methods, and explaining techniques for dating fossil material, the author persuades one that it does matter. Illustrations, diagrams, maps.