Grandmothers are important
2007-08-04 · Original WordPress address
Grandfathers, not so much:
In biological anthropology there is a Grandmother Hypothesis as an explanation for why adult human females live so long after their reproduction ceases, and, why menopause occurs in the first place (male fertility tapers off over time, while women undergo a concerted physiological change which shuts down their ability to reproduce). The basic idea is that beyond a particular age women can increase their own genetic fitness to a greater extent by investing in their daughters reproductive output.
This isn't true for grandfathers:
The relative lack of a strong effect suggests that the long lives of grandfathers are simply a byproduct of the long life of grandmothers (analogous to the breasts that males have), or, that in the relatively recent past males exhibited far higher reproductive skew (polygyny, etc.) which resulted in continuous reproduction through their lifetime.