Grandmother hypothesis and primate life histories

Abstract

The adaptive significance of midlife menopause in human females has long engaged the attention of evolutionary anthropologists. In spite of extensive debate, the problem has only recently been examined in the context of primate life histories. Here I extend those investigations by comparing life history traits in 16 primate species to test predictions generated from life history theory. In humans, late ages of maturity and higher than expected birth rates are systematically associated with extended postmenopausal longevity. Links among these adjustments on the primate pattern can explain how selection could slow somatic senescence without favoring extension of the fertile span. This conclusion is consistent with the observation that our fertile spans are similar to those of other pongids. The shape of the argument herein demonstrates the utility of life history theory for solving problems of adaptive evolution in female life history traits, with consequences for broader arguments regarding human evolution.