The human brain is one of the most intricate, complicated, and impressive organs ever to have evolved. Understanding its evolution requires integrating knowledge from a variety of disciplines in the natural and social sciences. Four areas of research are particularly important to this endeavor. First, we need to understand basic principles of brain evolution that appear to operate across broad classes of organisms. Second, we need to understand the ways in which human brains differ from the brains of our closest living relatives. Third, clues from the fossil record may allow us to outline the manner in which these differences evolved. Finally, studies of brain structure/function relationships are critical for us to make behavioral sense of the evolutionary changes that occurred. This review highlights important questions and work in each of these areas.