Shapes of Time explores evolution from a much neglected perspective that links natural selection and genetics. Kenneth J. McNamara delves into the living and the 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 may have developed less, looking more like overgrown juveniles.

McNamara shows how this phenomenon - known as heterochrony - has affected many aspects of evolution, including the mechanisms behind the selection of different breeds of animals, differences between sexes, and animal behavior. Heterochrony accounts for the "Peter Pan syndrome," in which some species look like their ancestors' young.

It explains what was really behind the evolution of flightless birds, how the dinosaurs got so big, how pterosaurs managed to produce wings supported only by their fourth fingers, and what has driven the evolution of the animal closest to our hearts - the primate species with the biggest brain and longest childhood - Homo sapiens.