Sci. Aging Knowl. Environ., 3 October 2001
Review Lectures on Senescence: I. The Causes of Aging
J. Maynard Smithhttp://sageke.sciencemag.org/cgi/content/abstract/sageke;2001/1/cp10
Abstract: Aging processes are defined as those that increase the susceptibility of individuals as they grow older to the factors that may cause death. Various possible theories of aging are considered, and evidence that may help to decide between them is discussed. Changes in different organ systems may be merely symptoms of some single aging process, or they may be largely independent and synchronized by natural selection. Even if different organ systems age independently, they may do so as a result of similar changes at a cellular level. Cellular theories of aging may have to take into account the effects of selection between the cells in a tissue.
The effects of radiation and somatic mutation theories of aging are discussed. It is suggested that radiation shortens life by inducing somatic mutations but that normal aging is not to any important extent caused by somatic mutations, although it may result from changes in cells that have effects on the physiology of the individual similar to those of somatic mutations. Evidence is presented that in Drosophila and in mice there are two phases in the life-span. In Drosophila, there is an initial "aging" phase, which is irreversible and occurs at a rate approximately independent of temperature, and a second "dying" phase, which is temperature-dependent in rate and reversible at lower temperatures.
Reproduced by permission.
J. Maynard Smith, Review Lectures on Senescence: I. The Causes of Aging. Proc. R. Soc. London Ser. B 157, 115-127 (1962).
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