Bigger brain, greater degree of sociability?

To answer these questions, a group of researchers from Stanford University, the London School of Economics, Harvard University and the University of Manchester have identified the social behaviours observed in 90 species of cetaceans, i.e. whales, rorquals, dolphins and porpoises. These behaviours include, for example, the presence of alliances within the group, care for young by individuals other than parents (alloparental care), inter-species cooperation, group hunting, social play, social learning and complex vocalizations.

The results show that brain structures that are quite different – in humans and cetaceans, for instance – can give rise to similar social skills. A little like the wings of birds and the “wings” of bats (which perform the same function, i.e. flight) are anatomically very different and the result of independent evolutions, separated in time by several millions of years.

“Let’s say a random increase in brain size or complexity gives you a greater capacity for social co-operation. If these new social skills pay off, then natural selection will keep favouring expansion of this same brain area. The capacity for social skills and cooperation will expand in turn, and the cycle will repeat,” explains Fox in an interview with CBC News. “What you’ll eventually expect to see is that species that have large, complex brains will also tend to possess a wider repertoire of social behaviours – and this is exactly what we found among the whales and dolphins.”

However, as in the case of primates, diversity of social behaviours is not the only trait associated with the size of the cetacean brain. Researchers also found that cetaceans with larger brains tend to have a more varied diet and larger ranges.