Aging is now the main cause of disease worldwide, including heart disease and stroke, cancer, Alzheimer’s disease, lung disease, arthritis, and many more. But the causes of aging have remained one of the great unsolved mysteries in science—and the solution might hold the key to treating a vast number of maladies. This book offers an accessible yet rigorous account of recent research that has begun to unlock the biology of aging. David Gems—a research scientist with decades of experience in this field—surveys the major ideas and discoveries, including a new synthesis of understanding that represents a revolutionary breakthrough. Rooted in evolutionary theory and genetics, this new model explains how aging works, why it is determined by genes, and the ways it causes late-life disease. Besides discussing the scientific advances, Gems also considers their implications for how we perceive and live with aging, as well as the potential long-term consequences of this research. Written in an inviting, engaging style with literary, philosophical, and personal interludes, this book helps readers understand aging in terms of not only its underlying biology but also its deeper meaning. On Aging is at once an illuminating overview for general readers and an authoritative reference for students and practitioners in biology, medicine, and healthcare.