The success of the human species derives largely from an emphasis on behavioral flexibility. In particular, three behavioral traits appear to have been critical. One has to do with the evolution of the ability to share resources, including through a dramatic expansion of the division of labor. Another has to do with the ability to think causally, so as to better predict future outcomes. The third involves the ability to communicate through language. Although much remains to be understood about the evolutionary changes in the brain that made these behavioral trends possible, we do have a general outline of the process. Research on brain evolution relevant to these behavioral changes will be reviewed, with a key conclusion being that these changes represent elaborations of evolutionarily older circuitry rather than through the evolution of entirely new circuits.