Social adaptation across domains of evolution

Adaptation is rarely for the good of an individual alone, but for the good of an individual and all her relatives—i.e., maximising inclusive rather than personal fitness. In this thesis, I use kin selection theory to consider how social adaptation has driven the evolution of new domains of life—such as cells, multicellularity, and eusociality—and how it can operate across multiple dimensions, including space and time. First, I examine the evolution of cooperation among early replicators housed within protocells. Using an evolutionary invasion analysis, I show that cooperative mutants can invade when protocell permeability is low, and that protocells containing larger populations of replicators achieve the greatest system-level growth. These results raise the question as to whether there may be a selective advantage for cells with low permeability and larger genomes. Second, I consider the evolution of division of labour during the emergence of organismality in the transition to multicellularity. I recover Michod’s ‘group covariance effect’, but propose an alternative interpretation that does not treat it as an emergent property of the group. In doing so, I also identify a ‘clonality window’ that allows for the evolution of obligate multicellularity. Third, I extend an existing formalism of group-level adaptation to incorporate class structure, explicitly modelling reproductive and non-reproductive classes to capture the original superorganisms: obligately eusocial colonies. Finally, I investigate the social evolutionary causes and consequences of dormancy. I derive dormancy analogues of several classic results for dispersal, demonstrating that dormancy—conceptualised as dispersal through time—plays a similar role in social evolution as dispersal in space.