(Mwenza Blell’s post from The WILEY FREE ONLINE LIBRARY.)
The grandmother hypothesis is a hypothesis to
explain the existence of menopause in human life history by identifying the
adaptive value of extended kin networking. It builds on the previously
postulated "mother hypothesis" which states that as mothers age, the
costs of reproducing become greater, and energy devoted to those activities
would be better spent helping her offspring in their reproductive efforts.
It suggests that by redirecting their energy onto
those of their offspring, grandmothers can better ensure the survival of their
genes through younger generations. By providing sustenance and support to their
kin, grandmothers not only ensure that their genetic interests are met, but
they also enhance their social networks which could translate into better
immediate resource acquisition. This could extend past kin into larger
community networks and benefit wider group fitness.
The grandmother hypothesis is an adaptationist explanation for the fact that the human female life span extends beyond the period of fertility. Human female reproductive life spans are variable in length but reproductive senescence occurs much faster than somatic aging.