Our bodies evolved over eons, slowly calibrating to the African savanna on which 98 percent of our ancestors lived and died. So, too, did our brains. Evolutionary psychology postulates that the mind is shaped by pressure to survive and reproduce. We jealously guard romantic partners and cherish our closest relatives above all others, lest we fail to pass on our genes. We easily acquire language, which is critical for cooperation and hence survival. Evolutionary psychology acknowledges these forces but stresses the ultimate (and largely unconscious) gene's eye view of behavior.