This text explores evolution down an avenue that links natural selection and genetics - the effect of changes to the rates and timing of growth and development. It delves into the living and fossil worlds to show how animals and plants have evolved when the carefully orchestrated pattern of embryological development is gently nudged off course - producing species that may have developed "beyond" their ancestors, or others that have developed less, looking more like over-grown juveniles. McNamara shows how this phenomenon - known as heterochrony - has affected many aspects of evolution, including the mechanism behind the selection of different breeds of animals, differences between sexes, and animal behaviour. Heterochrony accounts for the "Peter Pan syndrome," in which some species look like their ancestors' children. It explains what was really behind the evolution of flightless birds, how the dinosaurs got so big, how pterosaurs managed to produce a wing supported only by their fourth fingers, and what has driven the evolution of the animal closest to our hearts - the largest primate species with the biggest brain and longest childhood - Homo sapiens.