Is he right? Ridley, a science writer who has written previous books on genetic issues, certainly makes a good argument for the importance—and excitement—of his topic. Each chapter of the book corresponds to one of the chromosomes, focusing on one or more genes associated with it for the purpose of exploring a particular issue. Some chapters focus on our prehistory, for example, while others explore topics such as aging, intelligence, memory, disease, personality, stress, conflict, and sex. In addition, Ridley describes the process by which the information was obtained and the people most responsible for our progress in each area. All of these themes are intertwined in a casual style of storytelling that makes complicated material quite understandable.