The traditional emphasis on human nature as the foundation of politics needs to be reexamined from the perspective of contemporary biology. Because biological processes operate independently on the individual, the social group, and the species, an evolutionary approach to both observational research and cost-benefit analysis does not entail reductionism. Selfishness and altruism, participation in social groups, languages and cultures, and the rise and fall of centralized states can all be illuminated by empirical evidence and theories in the life sciences. For political philosophy, a new “naturalism” points to a return to the Aristotelian view that values or standards of judgment have rationally intelligible foundations, thereby challenging the relativist or nihilistic orientation that has characterized most contemporary thought.