The Body: A Guide for Occupants

by Bill Bryson

Menopause is as much a mystery as aging itself. Two principal theories have been advanced, known rather neatly as the mother hypothesis and the grandmother hypothesis. The mother hypothesis is that childbearing is dangerous and exhausting, and it becomes more of both as women age. So menopause may simply be a kind of protection strategy. By no longer having the wear and distraction of further childbirth, a woman can better focus on maintaining her own health while completing the rearing of her children just as they are entering their most productive years. This leads naturally to the grandmother hypothesis, which is that women stop breeding in middle age so that they can help their offspring raise their children. It is a myth, incidentally, that menopause is triggered by women exhausting their supply of eggs. They still have eggs. Not many, to be sure, but more than enough to remain fertile. So it isn’t the literal running out of eggs that triggers the process (as even many doctors appear to believe). No one knows exactly what is the trigger.