Professor Robin Dunbar, Director of the Institute of Cognitive and Evolutionary Anthropology, University of Oxford

Abstract: Human behaviour ultimately depends on the human mind, and this in turn in part reflects the brain that lies behind it. Humans have the largest brains relative to body size of any animal species, and within primates the largest absolute brains. The major evolutionary pressure for increases in brain size has been to cope with the demands of sociality. Through the course of human evolution, this seems to have been associated mainly with a progressive increase in social group size. However, the relatively large communities characteristic of modern humans imposes significant demands in terms of social cohesion, that we have had to solve by a number of sometimes rather simple mechanisms. I shall illustrate how several of these work, and draw out some of the implications for moral behaviour that seem to arise from this.