On Becoming Modern

Human social evolution is determined by demography. Unlike other animals, humans cooperate with nonrelatives in coordinated actions, decorate their bodies, build complex artefacts (useful or otherwise), talk, and divide themselves into linguistic groups. To understand the evolutionary basis of such behaviors, anthropologists must consider not only issues connected to social evolution in animals, but also the implications of the possible coevolution of genes and culture. Two articles in this issue examine aspects of human social evolution: On page 1293, Bowles (1) investigates the origins of altruism toward one's own social group, while on page 1298, Powell et al. (2) study the emergence of cultural complexity. Based on empirical evidence and modeling, both studies suggest that the demographic structure of our ancestral populations determined how social evolution proceeded.