Social Brain Hypothesis: A Survey of Evidence

The social brain hypothesis was first proposed to explain the remarkable cognitive abilities of primates and has since been extended to other taxa. Generally, it posits that sociality is a major selection pressure driving the evolution of large brains and intelligence. However, there is no single version of the hypothesis and different underlying mechanisms have been proposed. Tests of the hypothesis rely on appropriate indices of social complexity and brain size, as a proxy for cognitive abilities, and difficulties are associated with choosing both these variables and obtaining precise data. Situation is further complicated by that fact that a multitude of factors potentially contributing to or constraining encephalization is highly intercorrelated. This bachelor's thesis reviews approaches to research in this field and presents a survey of relevant evidence accumulated so far. The social brain hypothesis has been tested in various ways in primates, carnivores, ungulates, cetaceans, insectivores, bats, birds, fish (cichlids), and insects. The jury is still out, since contrasting results exist for most of these groups, warranting more research to help elucidate the influence of sociality on brain evolution