Evolution of human lifespan: Past, future, and present.

Abstract

The only satisfactory general theory for understanding the biology of aging is that provided by evolutionary genetics. The central theoretical result of the evolutionary theory of aging is that aging is caused by a fall in the force of natural selection, beginning at the time of the onset of reproduction and continuing until the cessation of reproduction. This formal result has been tested using breeding experiments in which the force of natural selection is altered in replicated laboratory populations. As predicted by the evolutionary theory of aging, such experiments can readily postpone aging. A recent advance has been the discovery of late-life mortality plateaus in human and other populations. These can be predicted theoretically from the late-life plateau in the force of natural selection, when it remains at or near zero. It is virtually certain that human lifespan has substantially increased over its last few million years of evolution. Evolutionary theory can explain this increase in terms of decreased ecological vulnerability resulting from increased brain size. The immediate future of human evolution is unlikely to see extensive genetic increases in lifespan, given the experimental data on rates of change in lifespan with experimental populations. But, evolutionary research suggests that there are few fundamental biological barriers to the extension of human lifespan, only practical barriers. Am. J. Hum. Biol. 10:409-420, 1998. © 1998 Wiley-Liss, Inc.