Social group formation

Abstract

Pathways of social group formation are poorly known for the origin of the eukaryotic cell, sexual reproduction, and many interspecific mutualisms. In the origin of multicellularity and eusociality, social group formation has usually occurred via a subsocial pathway (association of parents and offspring), with a semisocial pathway (association of same-generation organisms) occurring occasionally. The essential genetic condition for social group formation in groups exhibiting altruism is that relatedness should be positive – a prediction overwhelmingly supported by available evidence in the case of both the origin of multicellularity and the origin of eusociality. Non-genetic factors (ecological or synergistic) facilitate social group formation by increasing the benefits of grouping and the costs of living singly. Ecological factors promoting the formation of multicellular organisms and eusocial societies include environmental stresses and predator pressure. A major synergistic factor promoting the formation of multicellular organisms, eusocial societies, and interspecific mutualisms is division of labour.