Evolutionary significance of menopause.

The puzzle

Most mammals reproduce until late in life. Wild chimpanzees rarely show a long, healthy post-reproductive period of the human kind. If genes only “care” about more births, stopping ovulation decades before death looks wasteful. George Williams posed related life-history problems through antagonistic pleiotropy: a trait can be favoured early in life even if it costs later.

Humans also have unusually long childhoods and high-cost children. Menopause belongs with that slow life history.

Main hypotheses

• Grandmother hypothesis (Kristen Hawkes): Among the Hadza and in other foraging data, older women collect food and support grandchildren. Extra calories raise the survival of kin who share the grandmother’s genes. Selection then favours a long healthy life after fertility ends. This is inclusive fitness, not sentiment.
• Mother hypothesis: Stopping further births reduces the risk that a late pregnancy kills a woman who already has dependent children. The existing brood is protected.
• Embodied capital and pairing: Long adult life, male provisioning and pair bonds (as in some models by Hill and Kaplan) make a three-generation economy possible. Menopause is one piece of that package, not a lone mutation.
• What it is not: A simple pathology of ageing. If it were only decay, we would not expect the regular mid-life shift plus decades of useful work.

Killer whales are sometimes cited as another menopause case. They are a comparison, not the human explanation.

Evolutionary significance

Menopause marks humans as cooperative breeders with stacked generations. It helps explain childhood, longevity and female social value after childbearing. It also warns against reading every sex difference as a Victorian “woman’s nature”. The trait is about kin investment and life history.