Abstract

I will begin with a discussion and mathematical description of the two different types of social construction: `staying together’ and `coming together’ (or aggregation). Staying together means that individuals form larger units (complexes, groups) by not separating after reproduction (eg. ant colonies, most multicellular organisms), while coming together means that independent individuals form aggregates (eg. most animal groups, including humans). For each of these operations I will discuss its strengths and vulnerabilities in promoting social behavior, which will lead naturally into a discussion of the various mechanisms (and the relationships between them) that have been proposed to explain the evolution and maintenance of social behavior and cooperation: direct and indirect reciprocity, kin selection, group/multilevel selection, spatial structure, punishment/ostracism, rewards. I will discuss the theoretical frameworks in which these mechanisms are generally studied and for each mechanism I will present a simple model that captures the essence of how it can be described mathematically. Examples will be given from multicellularity, eusociality, bacterial biofilms, animal and human behavior.