Grandmothers and the evolution of human longevity: A review of findings and future directions

Abstract

Women and female great apes both continue giving birth into their forties, but not beyond. However humans live much longer than other apes do. Even in hunting and gathering societies, where the mortality rate is high, adult life spans average twice those of chimpanzees, which become decrepit during their fertile years and rarely survive them. Since women usually remain healthy through and beyond childbearing age, human communities include substantial proportions of economically productive postmenopausal women. A grandmother hypothesis(8-12) may explain why greater longevity evolved in our lineage while female fertility still ends at ancestral ages. This hypothesis has implications for the evolution of a wide array of human features. Here we review some history of the hypothesis, recent findings, and questions for ongoing research.

Ecological Knowledge, Leadership, and the Evolution of Menopause in Killer Whales

“…There is mounting evidence that menopause evolved via inclusive fitness benefits gained by helping kin; both postreproductive humans [11][12][13][14] and killer whales [15] increase the reproductive success and/or survival of their relatives. But how postreproductive females help their kin remains enigmatic.…”

Matrilateral Bias in Human Grandmothering

“…Finally, according to the "grandmother hypothesis" (Hawkes and Coxworth, 2013), senior women have evolved to be grandmothering specialists. The human female's efficacious postreproductive lifespan is unique; in all other primates, reproductive capability and other physiological systems tend to fail more or less simultaneously.…”

Grandmothering life histories and human pair bonding

“…Exceptional longevity with a distinctive postmenopausal life stage (7)(8)(9) may have evolved in our lineage when grandmothers' subsidies for weaned dependents allowed mothers to have next babies sooner. According to this grandmother hypothesis (10)(11)(12)(13)(14)(15)(16), longevity increased as longer-lived grandmothers could help more and so left more longer-lived descendants of both sexes. Women's postfertile life stage (7) produces a bias in the sex ratio of fertile adults with repercussions for male strategies.…”