Menopause: An evolutionary perspective

Evolutionary biologists classify theories of menopause as either: 1) adaptive, suggesting that female reproductive cessation results from its selective advantage, in that the increased risk of personal reproduction late in life makes it biologically more advantageous to rechannel reproductive energy into helping existing descendents, or 2) nonadaptive, indicating menopause is an artifact of the relatively recent dramatic increase in human longevity. With the possible exception of pilot whales, no mammals studied to date are known to commonly exhibit reproductive cessation in nature. To demonstrate adaptive menopause, one would need to establish both that the longevity of preagricultural humans commonly allowed them to exhibit menopause, and that postreproductive females could assist their descendents sufficiently to compensate for the loss of personal reproduction. The data on longevity of preagricultural humans with respect to the adaptive menopause hypothesis are mixed. Evolutionary models evaluated with data from modern hunting-gathering or agricultural humans fail to find that humans can assist their descendents sufficiently to offset the evolutionary cost of ceasing reproduction. However, assuming the human body has been physiologically adapted to the conditions extant during the vast majority of human history, it may be well worth pursuing how the signs and symptoms of menopause are affected by dietary, exercise, and reproductive hormone regimes mimicking those of the late Paleolithic era.