Integrating insights across diverse taxa: challenges for understanding social evolution

While it is broadly true that all sexually reproducing organisms have a “social life” (Trivers, 1985), social behaviour outside courting and mating is not the modal animal lifestyle. Nevertheless, there is remarkable phylogenetic breadth and evolutionary convergence of the diverse forms of social behavior (e.g., Wilson, 1975), perhaps helping explain why it has captured the enduring attention of the curious. Social behavior is especially puzzling from an evolutionary perspective in at least two ways. The first reflects a Public Goods or Tragedy of the Commons dilemma (e.g. Rankin et al., 2007): although social individuals can benefit from the underlying cooperation among group members, they are nonetheless susceptible to exploitation. The second perspective, arguably attracting far greater attention, concerns reproductive altruism – the question why individuals might forgo personal reproduction in order to assist the reproductive output of others. These two issues are not mutually exclusive: social systems that involve reproductive altruism are also vulnerable to commons tragedies. Nor are they particular to a given taxonomic group.