Sociality Did Not Favor Increases of Brain Sizes

Since the beginning of time, people have been fascinated with the fact that animals living in large herds, troops, or packs showed obvious signs of intelligence. When science evolved, experts hypothesized that it was the very trait of living together as a society (sociality) that triggered such massive improvements in the brain, in order to aid the animals in getting along. However, a new study, which will be unveiled in this week's issue of the Proceedings of the National Academy of Science, shows that the degree of sociality that animals have is not directly correlated with their brain levels.

Additionally, Evolutionary Biologists John Finarelli, from the University of Michigan, and John Flynn, from the American Museum of Natural History, showed that the development of a larger brain in most social species came as a result of evolutionary behavior, and not because of the pack or herd itself. “The universality of the Social Brain Hypothesis does not apply. When you look at relative brain size from the point of view of the entire evolutionary history of the clade, the story starts to fall apart – at least in carnivores. This study shows that, almost assuredly, brain size is increasing for different reasons in different groups of carnivores,” Finarelli said.

“When you analyze carnivores group by group, canids alone are responsible for the pattern seen in the recent analysis of the Social Brain Hypothesis,” his colleague added. Regardless of the fact that the animals grow together, they do not influence each other's development to a very wide extent. However, after numerous generations, genetic adaptations do occur, in which the parent-animals begin to endow their children with certain genes that encode social behavior. Still, the researchers showed that this type of behavior could be learned from the natural course of evolution as well, and not just from a large group.

“This is a sophisticated and powerful analysis that integrates fossils with extant species of carnivores. If you only analyze living forms, you often don't correctly reconstruct the evolutionary transformations. Our research shows another example of this, and indicates that the Social Brain hypothesis does not hold for all Carnivora,” Flynn explained. The experts also said that the correlations that existed between the animal brain size and the amount of time the beasts spent together could not be ignored, but that they were much less important than the role evolution played.