The story of human evolution has been told hundreds of times, each time with a focus that seems most informative of the teller. No matter how it is told the primary characters are rarely mothers and infants. Darwin argued survival, but today we know that reproduction is what evolution is all about. Centering on this, Trevathan focuses on birth, which gives the study of human evolution a crucial new dimension. Unique among mammals, humans are bipedal. The evolution of bipedalism required fundamental changes in the pelvis and resulted in a narrow birth canal. Humans are also large-brained...