Life history theory and human evolution : a chronicle of ideas and findings

Fertility ends at similar ages in women and female chimpanzees, but humans usually live longer and mature later. We also differ from our closest living relatives in weaning infants before they can feed themselves. The comparisons pose questions about when and why the distinctively human life history traits evolved in our lineage. Here I outline the basic framework of the field of life history evolution and, against that background, chronicle past inquiries into each of these distinctively human traits. The chronicle covers discovery and description, guided sometimes by hypotheses about underlying developmental mechanisms and sometimes by hypotheses about adaptive effects. Following the review, I discuss the continuing importance of distinguishing between questions about mechanisms and adaptive effects in light of accumulating fossil evidence and progress in genomics. I conclude with a brief reference to the most influential adaptive hypothesis to date, the Hunting hypothesis, and some of the accumulating empirical challenges to it, setting the stage for current debates addressed in subsequent chapters.