One question that has always bothered philosophers is why, as they grow old, people become enfeebled and die. One answer given was, "For the good of the species." That by dying, the old make room for the young. The trouble is, there didn't seem to be a mechanism for this, natural selection working on individuals, with any gain for the species being a happenstance byproduct.
An answer has been suggested, however. The critical time in
people's lives, from the point of view of natural selection, is in the few years
immediately after they reach physical maturity and reproductive age. The more fit they
are during that time, the more surviving young they leave, on average, the very crux of
natural selection. If all resources are thrown in to make this time successful, it may
be at the expense of later years when the cost, in terms of reproduction, is less. An
analogy might be parents who put all their earnings into supporting their offspring,
only to eke out their golden years in poverty, no resources having been saved for
retirement.
Listen to the Audio (mp3 format) as recorded by KTEP, Public Radio for the Southwest.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.
Williams, G. C. 2004. Stretching the limits of evolutionary biology. Science 304.