AI Insight
This study uses mathematical modeling to explain why menopause evolved in humans and some whales but not other mammals. The researchers found that menopause is favored by natural selection when males stay in their birth group (are philopatric) and when post-reproductive females significantly improve the survival of their sons and grandsons through caregiving. The model successfully predicted the timing of menopause in humans and killer whales using real demographic data from eight mammalian species.
Why it matters
Understanding why menopause exists helps explain human aging, family structures, and intergenerational care across species. The findings suggest that the extended post-reproductive lifespan in humans evolved because grandmothers and mothers provided critical survival benefits specifically to male descendants in ancestral populations where sons remained in their natal groups.
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⚠️ Preprint – Noch nicht peer-reviewed
Dieser Artikel wurde noch nicht von unabhängigen Experten begutachtet. Die Ergebnisse sind vorläufig und sollten mit Vorsicht interpretiert werden.
Post-reproductive lifespan is an evolutionary puzzle. In most mammals female fertility tracks survival, yet humans and a few toothed whales show survival after reproduction ends. Explaining when and why post-reproductive lifespan evolves is central to understanding the evolution of ageing, social structure, and intergenerational helping across species. Kinship-dynamics theory predicts that when males are philopatric, a females local relatedness – especially to male descendants – increases with age, potentially favoring late-life helping over continued reproduction. We develop an age-sex-structured kin-selection model to test whether a rare menopause-inducing modifier allele can invade an initially non-menopausal population through its direct effects on survival and fecundity and its indirect effects on relatives. We consider two evolutionary pathways: stop early, where reproduction ceases earlier with little change in lifespan, and live long, where lifespan extends beyond reproduction under disposable-soma trade-offs. Parameterized with demographic, dispersal, and helping-effect estimates from eight mammalian taxa, the model predicts empirically plausible ages of reproductive cessation and post-reproductive representation in humans and killer whales, but no invasion across plausible cessation ages in non-menopausal taxa. Global sensitivity analyses identify male dispersal and the effect of post-reproductive help on male survival as determinants of whether menopause evolves, motivating the mamas boy hypothesis: menopause is most strongly favoured by selection when late-life care increases the survival and lifetime fitness of philopatric sons and grandsons.