No abstract

Child death has played an important role in the evolution of humans. Of all stages of development, and at all historical times beyond Modern history, childhood has been associated with the highest levels of mortality. Compared to other evolutionary pressures such as surviving as an adult or finding a mate and having children, the odds of genetic failure (i.e., failure to directly contribute to one's genetic line) are greatest in childhood. The enormous potential evolutionary pressure exerted by child death should have significantly influenced human psychological adaptations. Despite this potential influence, child death may be one of the least studied influences on human evolutionary psychology. This paper discusses the historical rates of child mortality, the relative odds associated with passing on one's genes, adult mental adaptations to child mortality, and child mental adaptations to child mortality.

Evolutionary accounts of human traits are often based on proxies for genetic fitness (e.g., number of sex partners, facial attractiveness). Instead of using proxies, actual differences in reproductive success is a more direct measure of Darwinian fitness. Certain voice acoustics such as fundamental frequency and measures of health such as handgrip strength correlate with proxies of fitness, yet there are few studies showing the relation of these traits to reproduction. Here, we explore whether the fundamental frequency of the voice and handgrip strength account for differences in actual reproduction among a population of natural fertility humans. Our results show that both fundamental frequency and handgrip strength predict several measures of reproductive success among a group of indigenous Namibian females, particularly amongst the elderly, with weight also predicting reproductive outcomes among males. These findings demonstrate that both hormonally regulated and phenotypic quality markers can be used as measures of Darwinian fitness among humans living under conditions that resemble the evolutionary environment of Homo sapiens. We also argue that these findings provide support for the Grandmother Hypothesis.