Evolutionary theory in gerontology.

Abstract

PERSPECTIVES IN BIOLOGY AND MEDICINE Volume 25 ¦ Number 3 ¦ Spring 1982 EVOLUTIONARY THEORY IN GERONTOLOGY GEORGE A. SACHER* It is almost a century since August Weismann, the eminent German zoologist and early adherent to the Darwinian theory of evolution, published the first theory of the evolution of aging [1, 2].1 Other distinguished biologists have followed him in that quest, but the century-long effort to develop a satisfactory evolutionary theory of aging has been frustrated by the paradoxical and internally contradictory terms in which the problem is customarily formulated [3-5]. The paradox lies in the attempt to reconcile the deteriorative, disruptive processes of aging, senescent disease, and death with the evolutionary concepts of adaptation and selection for increased fitness. The publication of this paper is made possible by contributions made to the University of Chicago in memory of George Sacher after his death on January 24, 1981; it represents a memorial to this imaginative and creative scholar who contributed so much to the development of the theoretical analysis of problems in radiation toxicology, aging, and comparative biology. It is appropriate that the memorial contributions also be designated for the DwightJ. Ingle Writing Award ofPerspectives in Biology and Medicine, in the name of the friends of George Sacher, who was himself a lucid and provocative author. This paper, which is based on a lecture at the University of Rochester on Wilson Day, October 22, 1980, is published almost exactly as it was written by George Sacher for presentation in the Symposium on Theories of Aging, AAAS annual meeting, Toronto, January 4, 1981. The references have been added through the kindness of Drs. Ronald W. Hart, National Center for Toxicological Research, and George M. Martin, University of Washington School of Medicine, both longtime friends and collaborators of George Sacher . George would probably have revised his talk for publication. That was his custom, but we did not wish to change his words. *Division of Biological and Medical Research, Argonne National Laboratory, Argonne, Illinois 60439, and Committee on Evolutionary Biology and Committee on Human Development , University of Chicago, Chicago, Illinois 60637. 'Note the chapter titles in [2]: The duration of life (first published 1881), On heredity (first published 1883), Life and death (first published 1883), The continuity of the germplasm as the foundation of a theory of heredity (first published 1885), The significance of sexual reproduction in the theory of natural selection (first published 1886), and On the number of polar bodies and their significance in heredity (first published 1887). Copyright is not claimed for this article. Perspectives in Biology and Medicine, 25, 3 ¦ Spring 1982 | 339 I shall recount the history of biological theory on the evolution of aging from its beginnings to the recent developments in molecular genetics . I propose to show that some of the contradictions and fallacies in the evolutionary theory, and also in thinking about the biological nature of aging generally, arise from unverbalized preconceptions that have ancient roots in our cultural and religious traditions. I shall offer a new conceptualization of the phenomena of aging, longevity, and death that is consistent with the general principles of evolution and genetics and with modern molecular biology. Finally, and most important, I hope to convince you that this theoretical issue has real practical importance for our future progress in the control of aging and disease, and, moreover, that it has profound philosophical importance in regard to our understanding of how aging and mortality relate to the basic organization of living systems. In the course of a series of investigations in evolution and cell biology, including the development of his influential theory of the germ plasm, Weismann produced, beginning in 1881, several essays on the evolutionary significance of aging and death [2]. The essence of his theory is that aging is an adaptive characteristic, that is, contributes to the fitness of the species, and that it evolved as a means to assure the removal from the population of those individuals who had reached the end of their reproductive spans, so that they would no longer compete for food and space with their still fertile descendants. Natural selection can operate only if there are genetically controllable biochemical mechanisms that can modify...