In such a book it is impossible to cover all relevant topics in depth and therefore the object has not been to be comprehensive. Rather, it seemed better to outline the general principles and to provide sufficient references to allow readers to access further, detailed information if required. I would like to acknowledge the help of many of my colleagues in giving advice and reading through sections of text. Steve Brown helped with production of many of the graphs, Kath McDonnell and Carol Hole typed the manuscript, and John Conibear produced the final text figures from my original sketches. To these people I am especially grateful. Humans appear to be adapted to an omnivorous diet, based on the shape of their teeth and their unspecialized gut, and it is likely that quite early in human evolution meat began to play a part in our diet. Originally this would have been scavenged from the kills of more effective predators, such as the large cats, until hunting techniques developed.