An accessible introduction to the science of evolutionary psychology and how it explains many aspects of human nature. Unlike many books on the topic, which focus on abstractions like kin selection, this book focuses on Darwinian explanations of why we are the way we are--emotionally and morally--and interweaves episodes from Darwin's own life as illuminating examples. Wright deals particularly well with explaining the reasons for the stereotypical dynamics of the three big "S's:" sex, siblings, and society.