Big-Brained Cetaceans: How Does Social Living Contribute to Brain Expansion?

Big-Brained Cetaceans: How Does Social Living Contribute to Brain Expansion?

Contributed by Marielle Grenade-Willis

Many comparisons have been drawn between the socio-cognitive abilities of cetaceans and humans. The urge to anthropomorphize the experience of underwater mammals such as dolphins, orcas, and whales is understandably fitting as there are many parallels between their evolution and ours in terms of rich, social behavior. Similarities would include the capability to form intimate peer bonds, express unique linguistic dialects, and play with those around us. In a recent study published in the journal Nature Ecology & Evolution, data was collected on how exactly encephalization, the quality of brain expansion, developed in cetaceans. What was fascinating to discover is that there is a relationship between cetacean social structure and brain size in that “a diverse repertoire of social behaviors pays the greatest dividends when all individuals are recognizable to one another and interact regularly. These conditions are met when groups are cohesive and predictable. It it therefore reasonable that our results show that large relative brain size, cohesive social bonds, and broad social repertoires tend to co-occur in the same species”.

However, the study’s explanations for these “hyper-social” activities and their correlation to complex nervous systems, differ somewhat between primates and cetaceans. In primates, “nonsocial ecological factors” such as home range and varied foraging habits to adequately subsist a large brain, have also played a major role in how our complex brains have developed. In cetaceans, scientists argue that encephalization is not just a product of evolutionary pressure, but is a fluid adaptation to a socially rich environment requiring cooperation with known conspecifics. Evolution is not teleological, which is to say, that there is no definite end point to its many influences and ultimate manifestations. Understanding that cetaceans have the capability to support complex social structures does not mean we must proclaim that whales are “human-like”.