We may marvel at the process of an egg becoming an adult, but we accept it as an everyday fact. It is merely then a lack of imagination to fail to grasp how changes in this process that assimilated over long periods of time, far longer than the span of human experience, shape life's diversity."The book's second half is where Carroll really gets at the meat of evo devo, explaining how regulatory genes control such mysteries as individual and population changes in butterfly's spots, jaguar fur, and hominid skulls. Evo devo is one of the hottest areas of study in 21st-century biology, and Carroll's outline of the field is a great place to start understanding it. --Therese Littleton