Peccei J S
Department of Anthropology, University of California Los Angeles 90024-1429, USA.
Maturitas. 1995 Feb;21(2):83-9. doi: 10.1016/0378-5122(94)00884-a.
Menopause is widely believed by biological anthropologists and life history theorists to have arisen early in human evolution. In this paper, I suggest that female reproductive senescence was the result of the escalating energetic cost of gestation, lactation and childcare that accompanied the continuing encephalization of early hominid offspring and the ensuing increase in infant altriciality, or helplessness, and the concomitant prolongation of juvenile dependence. Natural selection favored females who became prematurely infertile, as the escalating cost of raising each offspring led to maternal depletion and made it more profitable in terms of lifetime reproductive success to continue investing in existing offspring rather than attempting late pregnancies. Results of a mathematical model are presented which show that reproductive senescence can be advantageous even when maximum potential lifespan is only 50 years, if the premature cessation of reproduction allows females to moderately increase the survival and fertility of their existing subadult offspring. These findings suggest that menopause could have originated as much as 1.5 million years ago, and that if menopause is indeed such an old trait, it was more likely the result of selective pressure on females to invest more in their own children, as opposed to their grandchildren.
生物人类学家和生命史理论家普遍认为，更年期在人类进化早期就已出现。在本文中，我认为女性生殖衰老的原因是随着早期原始人类后代脑容量的不断增大，婴儿变得更加早产或无助，以及随之而来的幼年期依赖期延长，妊娠、哺乳和育儿的能量消耗不断增加。自然选择青睐那些过早失去生育能力的女性，因为养育每个后代的成本不断上升导致母体资源耗尽，从终身繁殖成功率来看，继续投资于现有的后代而非尝试晚期妊娠会更有利可图。本文给出了一个数学模型的结果，该结果表明，如果生育过早停止能让女性适度提高现有未成年后代的存活率和生育能力，那么即使最大潜在寿命只有50岁，生殖衰老也是有益的。这些发现表明，更年期可能早在150万年前就已出现，而且如果更年期确实是一个如此古老的特征，那么它更有可能是女性面临选择性压力，要更多地投资自己的孩子而非孙辈的结果。
