This book presents a completely novel approach to understanding aging: it explains both why aging exists in animals and reviews our current understanding of it at the biological level. Dr. Holliday argues that much research needs to be done on the cellular and molecular aspects of aging if the origin of age-related diseases is to be understood. In making this argument, the author draws on material from a wide range of disciplines, including extensive biomedical information about age-related disease in humans. This thought-provoking book will appeal to all students and researchers who are interested in aging, whether they are working in the clinical or basic research sphere.