Why do we age? Is aging inevitable? Will advances in medical knowledge allow us to extend the human lifespan beyond its present limits? Because growing old has long been the one irreducible reality of human existence, these intriguing questions arise more often in the context of science fiction than science fact. But recent discoveries in the fields of cell biology and molecular genetics are seriously challenging the assumption that human lifespans are beyond our control.

With such discoveries in mind, noted cell biologist William R. Clark clearly and skillfully describes how senescence begins at the level of individual cells and how cellular replication may be bound up with aging of the entire organism. He explores the evolutionary origin and function of aging, the cellular connections between aging and cancer, the parallels between cellular senescence and Alzheimer's disease, and the insights gained through studying human genetic disorders--such as Werner's syndrome--that mimic the symptoms of aging. Clark also explains how reduction in caloric intake may actually help increase lifespan, and how the destructive effects of oxidative elements in the body may be limited by the consumption of antioxidants found in fruits and vegetables. In a final chapter, Clark considers the social and economic aspects of living longer, the implications of gene therapy on senescence, and what we might learn about aging from experiments in cloning.

This is a highly readable, provocative account of some of the most far-reaching and controversial questions we are likely to ask in the next century.

"Clark effortlessly takes readers from the simple to the complex, from a discussion of single-celled organisms to human beings.... He also does a nice job of exploring the causes of Alzheimer's disease, various forms of cancer and an array of genetic disorders that afflict the young by making them

age prematurely.... Neatly informative."--Publishers Weekly

"Why in spite of healthy, well-fed, well-watered lives do people age and die? The well-informed physician-researcher, William R. Clark, excitedly reveals new studies of progeric and normal mammals as he tracks the inevitable corollary to human life: the inexorable rhythmic march to human

death."--Lynn Margulis, Distinguished University Professor, Department of Geosciences, University of Massachusetts, Amherst and co-author of What is Life" and What is Sex"

"Fascinating and informative.... One of the book's most engaging elements is Clark's ability to show how scientists think about problems and approaches in the field."--Booklist

Professor Emeritus of Immunology at UCLA and an internationally recognized authority on cellular immune reactions, William R. Clark is the author of The New Healers: Molecular Medicine in the Twenty-First Century, Sex and the Origins of Death, and At War Within: The Double Edged Sword of Immunity, all published by OUP.

Acknowledgments

Introduction

1. Aging, Senescence, and Lifespan

2. The Nature of Cellular Senescence and Death

3. The Evolution of Senescence and Death

4. Of Embryos and Worms and Very Old Men: The Developmental Genetics of Senescence and Lifespan

5. Human Genetic Diseases That Mimic the Aging Process

6. Cycling to Scenescence

7. Replicative Immortality: Cancer and Aging

8. Caloric Restriction and Maximum Lifespan

9. With Every Breath We Take: Oxidative Stress and Cellular Senescence

10. The Aging Brain

11. A Conditional Benefit

Biblography

Index