From Publishers Weekly

Oxford University zoologist Parker tackles one of biology's biggest mysteries in this nontechnical account. He provides a relatively simple explanation for the sudden explosion of life forms that defines the boundary between the pre-Cambrian and Cambrian eras approximately 543 million years ago: "The Cambrian explosion was triggered by the sudden evolution of vision" in simple organisms. In Parker's "Light Switch" theory, active predation became possible with the advent of vision, and prey species found themselves under extreme pressure to adapt in ways that would make them less likely to be spotted. New habitats opened as organisms were able to see their environment for the first time, and an enormous amount of specialization occurred as species differentiated. Parker claims that his theory is far more robust than previous attempts to explain the surge in diversity, even those most recently advanced by proponents of a snowball earth (the theory presented by Gabrielle Walker in Snowball Earth). In readable prose, Parker provides detailed information on the fossil record as well as a wealth of interesting material on the role light plays in environments and how vision operates across a host of species. Although at times his tangents are a bit distracting, Parker's book will bring his controversial ideas to the general public.