Does such strategic use of valuable assets ever occur among animals? For example, do elders share in the stores accumulated by the coresident-favored offspring among bannertail kangaroo rats? And do animal children compete in some way for the right to inherit?

I have argued that postreproductive females and older males were quite prevalent in preagricultural human populations and that they probably raised the reproductive fitness of their children through leadership, knowledge, and food transfers. It is unknown, however, whether the longevity of humans can, in fact. be explained by the usefulness of older humans. The contribution of postreproductive humans to the reproductive fitness of their descendants is a necessary, but not sufficient, condition for the viability of an evolutionary explanation.

Austad (in this volume) concludes with the suggestion that if there is more field work linking transmission of assets to senescence in animals, then "a generalized theory of the ecology of resource transfer across generations may emerge." The study of the evolution of longevity together with a general study of intergenerational transfers does, indeed, appear to be a promising and fascinating area for further work.

Acknowledgment

I am grateful to Timothy Miller, Shripad Tuljapurkar, Kenneth Wachter, and two anonymous referees for comments during preparation of this chapter. Research for this paper was funded by a grant from National Institute on Aging (AG1 1761).

References

Acsadi. G., and J. Nemeskeri 1970 History of Human Life Span and Mortality. Budapest: Akademiai Kiado.


Becker, G.S. 1988   Family economics and macro behavior. American Economic Review 78(1 March):1-13.

Bhat, M.P. 1987   Mortality in India: Levels, Trends, and Patterns. Ph.D. dissertation, University of Pennsylvania.

Bongaarts, J. 1983  The proximate determinants of natural marital fertility. Pp. 61-102 in R. Bulatao and R. Lee, eds., Determinants of Fertility in Developing Countries Supply and Demand for Children, Vol. 1. New York: Academic Press.


Caldwell. J.C. 1976   Toward a Restatement of Demographic Transition Theory, Population and Development Review. Pp. 113-180 reprinted in (1982) J. Caldwell Theory of Fertility Decline. New York: Academic Press.

Carter. L., and R. Lee 1992   Modeling and forecasting U.S. mortality: Differentials in life expectancy by sex. In D. Ahlburg and K. Land, eds., Population Forecasting, a special issue of International Journal of Forecasting 14(3):393-412.



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement