It turns out brain size does correlate with group size: the neocortex, the part of our brain that deals with complex thinking and reasoning, grows in primates relative to the number of fellow primates they are likely to live with. Brains evolve to handle the number of social contacts we are going to have.

Aligned with this new direction, breakthroughs in our understanding of the prefrontal cortex, limbic system, and brainstem have revealed the human brain to be much more geared to social cognition, social