Department of Anthropology, University of Utah, Salt Lake City, UT 84112, USA.
Proc Natl Acad Sci U S A. 2010 May 11;107 Suppl 2(Suppl 2):8977-84. doi: 10.1073/pnas.0914627107. Epub 2010 May 5.
In the first paper to present formal theory explaining that senescence is a consequence of natural selection, W. D. Hamilton concluded that human postmenopausal longevity results from the contributions of ancestral grandmothers to the reproduction of their relatives. A grandmother hypothesis, subsequently elaborated with additional lines of evidence, helps explain both exceptional longevity and additional features of life history that distinguish humans from the other great apes. However, some of the variation observed in aging rates seems inconsistent with the tradeoffs between current and future reproduction identified by theory. In humans and chimpanzees, our nearest living relatives, individuals who bear offspring at faster rates do not cease bearing sooner. They continue to be fertile longer instead. Furthermore, within both species, groups with lower overall mortality rates have faster rates of increase in death risk with advancing age. These apparent contradictions to the expected life history tradeoffs likely result from heterogeneity in frailty among individuals. Whereas robust and frail alike must allocate investments between current and future reproduction, the more robust can afford more of both. This heterogeneity, combined with evolutionary tradeoffs and the key role of ancestral grandmothers they identify, helps explain aspects of human aging that increasingly concern us all.
在第一篇提出正式理论来解释衰老是自然选择的结果的论文中，W.D. 汉密尔顿得出结论，人类绝经后的长寿是由于祖母对其亲属的繁殖做出了贡献。随后，随着更多证据的出现，祖母假说得到了进一步的阐述，它有助于解释人类与其他大猿类在寿命和其他生命史特征上的区别。然而，一些观察到的衰老速度的变化似乎与理论中确定的当前和未来繁殖之间的权衡不一致。在人类和黑猩猩这两种与我们亲缘关系最近的灵长类动物中，生育速度较快的个体并不会更早地停止生育。相反，它们的生育能力会延长。此外，在这两个物种中，总死亡率较低的群体随着年龄的增长，死亡风险的增加速度更快。这些与预期的生命史权衡明显矛盾的现象可能是由于个体脆弱性的异质性造成的。虽然强壮和脆弱的个体都必须在当前和未来的繁殖之间分配投资，但强壮的个体可以在两者之间投入更多。这种异质性，加上进化上的权衡以及它们所确定的祖母的关键作用，有助于解释越来越引起我们关注的人类衰老的各个方面。
