Human Longevity at the Cost of Reproductive Success: Trade-Offs in the Life History

Abstract

A central concept in the evolutionary theory of senescence is the idea that ageing results from life-history trade-offs (Williams 1957; Kirkwood 1981; Kirkwood and Rose 1991; Rose 1991, Partridge and Barton 1993). In particular, the disposable soma theory (Kirkwood 1977, 1981; Kirkwood and Holliday 1979) suggests that longevity is determined through the setting of longevity assurance mechanisms so as to provide an optimal compromise between investments in somatic maintenance (including stress resistance) and in reproduction. A corollary is that species with low extrinsic mortality are predicted to invest relatively more effort in maintenance, resulting in slower intrinsic ageing, than species with high extrinsic mortality. Comparative studies among mammalian species confirm that cells from long-lived species appear to have a greater intrinsic capacity to withstand stresses than cells from short-lived species (Kapahi et al. 1999). Ecological comparisons support the idea that short-lived species invest in higher rates of reproduction — necessary because such species are generally subject to higher extrinsic mortality — leaving fewer resources available for somatic maintenance and repair.