John Tyler Bonner, one of our most distinguished and insightful biologists, here challenges a central tenet of evolutionary biology. In this concise, elegantly written book, he makes the bold and provocative claim that some biological diversity may be explained by something other than natural selection.

With his customary wit and accessible style, Bonner makes an argument for the underappreciated role that randomness--or chance--plays in evolution. Due to the tremendous and enduring influence of Darwin's natural selection, the importance of randomness has been to some extent...