Dieter Lukas, Postdoctoral Research Associate, Department of Zoology, University of Cambridge
A central aim of research in social evolution is to explain differences in the complexity of societies. Various measures have been developed to describe social complexity, but we still lack a full understanding of why societies differ in complexity and how these differences influence evolutionary processes. I draw on comparative studies of mammals to show that reconstructing how societies form provides insights into the rules that govern social interactions. These findings show that a distinction must be drawn between complexity in the structure of societies and complexity of relationships among group members. Societies with high structural complexity include several distinct castes and a clear division of labour, whereas when group members form differentiated bonds with each other societies have high relationship complexity. The placement of a society along these two opposing axes of complexity appears better explained by kinship than ecology. I discuss how this framework offers opportunities to understand the evolution of differences in the complexity of human societies.