An intense debate is raging within evolutionary anthropology as to whether the evolution of human behaviour is driven by selection pressure on the individual or on the group. Until recently there was consensus amongst evolutionary biologists and evolutionary anthropologists that natural selection caused behaviours to evolve that benefit the individual or close kin. However the idea that cultural behaviours that favour the group can evolve, even at the expense of individual well-being, is now being supported by some evolutionary anthropologists and economists. Models of cultural group selection rely on patterns of cultural transmission that maintain differences between cultural groups, because either decisions are based on what most others in the group do, or non-conformists are punished in some way. If such biased transmission occurs, then humans may be following a unique evolutionary trajectory towards extreme sociality; such models potentially explain behaviours such as altruism towards non-relatives or limiting your reproductive rate. However, relevant empirical evidence from real world populations, concerning behaviour that potentially influences reproductive success, is almost entirely lacking. The projects proposed here are designed to help fill that gap. In micro-evolutionary studies we will seek evidence for the patterns cultural transmission or social learning that enable cultural group selection to act, and ask how these processes depend on properties of the community, and thus how robust are they to the demographic and societal changes that accompany modernisation. These include studies of the spread of modern contraception through communities; and studies of punishment of selfish players in economic games. In macro-evolutionary studies, we will use phylogenetic cross-cultural comparative methods to show how different cultural traits change over the long term, and ask whether social or ecological variables are driving that cultural change.