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.
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William R. Clark is Professor Emeritus of Immunology in the Department of Molecular, Cell and Developmental Biology at the University of California, Los Angeles. He is the author of a number of books about biology, immunology, and evolution, including Sex and the Origins of Death, A Means to an End: The Biological Basis of Aging and Death, and The New Healers: The Promise and Problems of Molecular Medicine in the Twenty-First Century.
Professor Clark writes with elegance and employs a reasoned tone, but he is not always direct, and often expresses ideas in the understandably tentative way of a very exacting scientist. Consequently it is not easy to see that nowhere in this book does he directly say what causes aging and death. Nor does he simply say we don't know. What he does say is there are some persuasive theories, especially the evolutionary model began by Haldane and Medawar and refined by George Williams (pp. 49-50), that are consistent with the data that "may be essentially correct, at least in broad outline." (p. 52). Clark makes it clear that we have senescence effector genes in our cells but he doesn't say how they got there, only that they were "already in place in the earliest eukaryotic organisms such as paramecia and yeast." (p. 57) The reader is left to believe that there is a mechanism that retains them, but what that mechanism might be is unclear.
I am led to believe that senescence is built into our cells and is part of our genetic makeup. We are programmed to grow old and die. Just how is what Professor Clark is exploring here. He concentrates on the cellular level because it is his belief that this is where the mechanisms for senescence can be found. On page 190 he argues that senescence is genetically controlled and not the result of a random breakdown, citing the fact that "maximum lifespan is species-specific." In short, humans live a lot longer than dogs, contrary to what might be expected if senescence were caused by cells getting old and wearing out. He points out on page 48 that "mice and humans, although composed of proteins that are extremely similar at a chemical level, have both average and maximal lifespans differing by a factor of 30 or more."
Clark also covers in some detail such issues as the evolution of senescence, average and maximum lifespan; genetic diseases such as Werner's syndrome, the Hutchinson-Gilford syndrome and others; oxidative stress as a cause of cellular senescence and the use of Vitamin E and other antioxidants; the aging brain and Alzheimer's disease; cancer and the social and economic effect of humans living longer. A chapter is devoted to the phenomenon of increased lifespan through restricted caloric intake.
This is an authoritative and persuasive book, well written and well presented.
--Dennis Littrell, author of “Understanding Evolution and Ourselves”
This book is totally fascinating, and William R. Clark's "Sex and the Origins of Death" is one of the books that got me reading about science, but I can't read more than a page or two before I have to put it down. It strikes just a little too close to the heart - I don't find I'm able to detach myself enough from the emotional side of mortality and dying to really get absorbed in the science.
His writing is clear and focused and hits the balance between challenging the non-scientist reader and drowning her in particularized language and ideas.
This book is a good start if you want to know about the basics of aging, the evolutionary basis of aging, and why we age. It has actually made more interested in geriatrics and gerontology. The only problem I h ad with this book that it sometimes repeated itself, and wasn't always clear with how it presented itself.
Written in English, a bit out of date (Human Genome Project is now complete) but otherwise the concepts are relatively timeless. The last chapter drones on but otherwise it was worth my time.