School of Mathematics and Statistics, University of Sydney, NSW 2006, Australia.
School of Mathematics and Statistics, University of Sydney, NSW 2006, Australia.
J Theor Biol. 2019 Jan 14;461:84-91. doi: 10.1016/j.jtbi.2018.10.035. Epub 2018 Oct 16.
Great apes, the other living members of our hominid family, become decrepit before the age of forty and rarely outlive their fertile years. In contrast, women - even in high mortality hunter-gatherer populations - usually remain healthy and productive well beyond menopause. The grandmother hypothesis aims to account for the evolution of this distinctive feature of human life history. Our previous mathematical simulations of that hypothesis fixed the end of female fertility at the age of 45, based on the similarities among living hominids, and then modeled the evolution of human-like longevity from an ancestral state, like that of the great apes, due only to grandmother effects. A major modification here allows the age female fertility ends to vary as well, directly addressing a version of the question, influentially posed by GC Williams six decades ago: Why isn't menopause later in humans? Our model is an agent-based model (ABM) that accounts for the coevolution of both expected adult lifespan and end of female fertility as selection maximizes reproductive value. We find that grandmother effects not only drive the population from an equilibrium representing a great ape-like longevity to a new human-like longevity, they also maintain the observed termination of women's fertility before the age of 50.
大型猿类是我们人类家族中其他现存的成员，它们在四十岁之前就会衰老，很少能活过生育期。相比之下，女性——即使在高死亡率的狩猎采集人群中——通常在绝经后仍然保持健康和生育能力。祖母假说旨在解释人类生命史这一独特特征的进化。我们之前对该假说的数学模拟基于现生灵长类动物的相似性，将女性生育能力的结束年龄固定在 45 岁，然后从一个类似于大型猿类的祖先状态来模拟人类般的长寿进化，这完全是由于祖母的作用。这里的一个主要修改是允许女性生育能力结束的年龄也发生变化，直接解决了 GC 威廉姆斯六十年前提出的一个问题的一个版本：为什么人类的绝经期不会更晚？我们的模型是一个基于主体的模型（ABM），它考虑了预期成年寿命和女性生育能力结束的共同进化，因为选择最大化了生殖价值。我们发现，祖母的作用不仅推动了种群从一个类似于大型猿类的长寿的平衡状态进化到一个新的人类般的长寿状态，而且还维持了观察到的女性在 50 岁之前生育能力的终止。
