Grandmothering drives the evolution of longevity in a probabilistic model

Kim, Peter; McQueen, John S.; Coxworth, James E.; Hawkes, Kristen

doi:10.1016/j.jtbi.2014.03.011

Cited by 69 publications

(73 citation statements)

References 47 publications

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“…Elsewhere we have shown that simulations of this model result in two life history equilibria: a great ape-like one with no grandmothering and a human hunter-gatherer-like one when grandmothers' subsidies allow mothers to have next babies sooner (15). Not surprisingly, each equilibrium is associated with distinct, characteristic sex ratios in the fertile ages (Fig.…”

Section: Grandmothering Simulationsmentioning

confidence: 75%

“…We track mating sex ratios through simulations of an agentbased model first built to investigate the evolution of human longevity via grandmothering (13,15). For reasons elaborated below, we follow both the adult sex ratio (ASR), defined as the ratio of males to females in the fertile ages, and the operational sex ratio (OSR), which counts only the subset of adults currently capable of a conception (19) (see Supporting Information for model parameters and definitions).…”

Section: Grandmothering Simulationsmentioning

confidence: 99%

“…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.…”

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confidence: 99%

“…Here we simulate hominid mating sex ratios with an agent-based model of the evolution of human longevity via grandmothering (13,15). We then compare simulated sex ratios to demographic data from both great apes and human hunter-gatherers.…”

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confidence: 99%

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Grandmothering life histories and human pair bonding

Coxworth

Kim

McQueen

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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The evolution of distinctively human life history and social organization is generally attributed to paternal provisioning based on pair bonds. Here we develop an alternative argument that connects the evolution of human pair bonds to the male-biased mating sex ratios that accompanied the evolution of human life history. We simulate an agent-based model of the grandmother hypothesis, compare simulated sex ratios to data on great apes and human hunter-gatherers, and note associations between a preponderance of males and mate guarding across taxa. Then we explore a recent model that highlights the importance of mating sex ratios for differences between birds and mammals and conclude that lessons for human evolution cannot ignore mammalian reproductive constraints. In contradiction to our claim that male-biased sex ratios are characteristically human, female-biased ratios are reported in some populations. We consider the likelihood that fertile men are undercounted and conclude that the mate-guarding hypothesis for human pair bonds gains strength from explicit links with our grandmothering life history.grandmother hypothesis | human life history | human evolution | mate guarding | mating sex ratios W e call attention to evidence that connects the evolution of human pair bonds to the male-biased sex ratios in fertile ages that characterize human populations. As in mammals generally, age-specific mortality is higher in males than in females (e.g., refs. 1-3). However, this difference is overshadowed by a distinctive feature of human life history: Oldest ages at parturition are about the same in humans as in other living hominids, the great apes (4, 5), whereas longevity is substantially greater and male fertility continues to older ages (6). Exceptional longevity with a distinctive postmenopausal life stage (7-9) may have evolved in our lineage when grandmothers' subsidies for weaned dependents allowed mothers to have next babies sooner. According to this grandmother hypothesis (10-16), 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. As longevity increased, olderaged males expanded the pool of competitors for the still-fertile females. With more competitors for each paternity, males' average success in finding new mates inevitably declined until defending a current mate became the better option. Our distinctive life history thus supplies previously unrecognized support for a mate-guarding hypothesis for the evolution of human pair bonds.Here we simulate hominid mating sex ratios with an agent-based model of the evolution of human longevity via grandmothering (13, 15). We then compare simulated sex ratios to demographic data from both great apes and human hunter-gatherers. Having identified the human bias, we connect it to increased male payoffs for mate guarding, noting some broad patterns in humans, the tradeoffs observ...

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Section: Grandmothering Simulationsmentioning

confidence: 75%

Section: Grandmothering Simulationsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Grandmothering life histories and human pair bonding

Coxworth

Kim

McQueen

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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“…Then the few older females still surviving as their fertility declined could increase their fitness in a novel way; and those novel benefits at older ages resulted in selection for increased somatic maintenance and repair. In simulations of Peter Kim's two-sex agent-based model of the grandmothering scenario (11,12), even very weak grandmothering drives populations from an ancestral ape-like equilibrium to a human-like one. At the ancestral equilibrium fewer than 1% of the adult females are past their fertility, but their helpful grandmothering drives populations to a new equilibrium with about 40% of the adult females past their fertility, very like the age structures of modern hunter-gatherers.…”

Section: How Old Is Human Longevity?mentioning

confidence: 99%