Sociobiology 4: The Grandmother Hypothesis

Why human beings have menopause is a puzzle for the sociobiological paradigm. It would seem, on the face of it, that women would be more likely to pass on their genes if they kept having more kids until they died. Yet they stop having the ability to have children decades, in most cases, before they die. It is an axiom of the theory that universal features of human mating and childrearing are not likely to be accidents. There must be a reason for menopause.

The grandmother hypothesis is that women (and their husbands) are more likely to see their line of progeny live and prosper if they stop having new kids, and help their children raise their grandchildren. Menopause is almost unique to human beings. But human beings also take forever to grow up, compared to other primates, and indeed compared to practically all other animals. Chimpanzees, for example, could raise children to sexual maturity, and if calamity should wipe out all the kids, could raise another whole family to sexual maturity. With human beings, though, the time scale for raising a generation is not three years but twenty. So it would make sense, it would be a reproductive advantage, to grandmothers to help raise their grandchildren.

It is also, of course, a huge help to mothers to have help from their mothers. These days we often hear the proverb "it takes a village to raise a child." The single most helpful person in most mothers' villages is her own mother. All three generations benefit in clear material and emotional ways from helpful grandmothers.

The grandmother hypothesis makes real-world sense. It also does what any good scientific theory does – it solves a puzzle generated by the larger paradigm. We can't regard it as proven yet, but I think it is a very promising thesis, and well worth teaching.

Menopause is not a bug; it's a feature.