Despite longstanding hostility to the biological explanation of human behavior, there are presently three general research programs aimed at the study of genetic influences on behavior: sociobiology and evolutionary psychology, behavioral genetics, and developmental psychobiology. Evolutionary psychology and its forebear, sociobiology, aim to discover species-typical traits that are adaptations (that is, traits that are in most cases the result of natural selection): Why do humans behave aggressively? What is the evolutionary source of altruism? Behavioral genetics aims primarily to uncover and disentangle genetic contributions (as distinct from environmental contributions) to individual differences in behavior: What are the predictors of aggressive versus nonaggressive behavior? Why does one person perform well on an IQ test, and another not? Developmental psychobiology aims to elucidate developmental pathways to particular behaviors: What is the mechanism by which organisms come to behave aggressively? What are the determinants of central nervous...