Rethinking the evolutionary theory of aging: Transfers, not births, shape senescence in social species
- Departments of Demography and Economics, University of California, 2232 Piedmont Avenue, Berkeley, CA 94720-2120
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Edited by Samuel H. Preston, University of Pennsylvania, Philadelphia, PA (received for review January 16, 2003)
Abstract
The classic evolutionary theory of aging explains why mortality rises with age: as individuals grow older, less lifetime fertility remains, so continued survival contributes less to reproductive fitness. However, successful reproduction often involves intergenerational transfers as well as fertility. In the formal theory offered here, age-specific selective pressure on mortality depends on a weighted average of remaining fertility (the classic effect) and remaining intergenerational transfers to be made to others. For species at the optimal quantity–investment tradeoff for offspring, only the transfer effect shapes mortality, explaining postreproductive survival and why juvenile mortality declines with age. It also explains the evolution of lower fertility, longer life, and increased investments in offspring.
Footnotes
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↵ † E-mail: rlee{at}demog.berkeley.edu.
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This paper was submitted directly (Track II) to the PNAS office.
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See commentary on page 9114.
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↵ ‡ The selection effect on this mutation depends both on the size of the shifts in the two curves and on the slopes of the two curves, as can be seen formally in the mathematical analysis. The shifts need not be parallel as drawn here, and selection will act on mutation-driven changes in the slopes as well.
- Copyright © 2003, The National Academy of Sciences
