Human brains are much larger than one would expect for primates of our body size. They also feature more neurons and a proportionately larger neocortex. Prefrontal cortex, in particular, is significantly larger in humans than in other species. Although these features make the human brain unique, most of them are in line with allometric expectations, meaning that they can be predicted from the large size of our brains. Thus, human brains are fairly typical primate brains; they just became unusually large. Nonetheless, there are good reasons to believe that the evolutionary expansion of the human brain, especially of prefrontal cortex, caused evolutionary changes in neural connectivity and function. Dr. Striedter will review some of the evidence supporting this idea and place it in the larger context of brain and behavioral evolution.