This paper first considers the implications of biological evolution for economic preferences. It analyzes why utility functions evolved, considers evidence that utility is both hedonic and adaptive, and suggests why such adaptation might have evolved. Time preference and attitudes to risk are treated--in particular, whether the former is exponential and the latter are selfish. Arguments for another form of interdependence--a concern with status--are treated. The paper then considers the evolution of rationality. One hypothesis examined is that human intelligence and longevity were forged by hunter-gatherer economies; another is that intelligence was spurred by competitive social interactions.