Primates are an intensely social order of animals showing wide variation in group size, organization and structure. Using an evolutionary perspective, this course will focus on why primates form groups and how their relationships with different individuals are maintained, with reference to other orders of animals. In particular, this course examines how different forms of cooperation evolve when natural selection is often thought to maintain only selfish behaviours. The form and function of different social systems, mating systems, and behaviours will be examined.