Biodemography, the mating of biology and demography

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Abstract

Old-age survival has increased substantially since 1950. Death rates decelerate with age for insects, worms, and yeast, as well as humans. This evidence of extended postreproductive survival is puzzling. Three biodemographic insights-concerning the correlation of death rates across age, individual differences in survival chances, and induced alterations in age patterns of fertility and mortality-offer clues and suggest research on the failure of complicated systems, on new demographic equations for evolutionary theory, and on fertility-longevity interactions. Nongenetic changes account for increases in human life-spans to date. Explication of these causes and the genetic license for extended survival, as well as discovery of genes and other survival attributes affecting longevity, will lead to even longer lives.

Humanity is aging. The social, economic, and health-care consequences of the new demography (Table 1) will drive public policy worldwide in coming decades [1]. Growth of the older population is fueled by three factors. Baby-boom generations are growing older. The chance of surviving to old age is increasing. And the elderly are living longer-because of remarkable, largely unexplained reductions in mortality at older ages since 1950 [2-4]. Biodemography, the mating of biology and demography, is, we argue, spawning insights into the enigma of lengthening longevity [5].