Intellectual capacity is traditionally measured by intelligence tests, though there is much disagreement about the nature of intelligence, how (and whether) it should be measured, whether there are multiple intelligences, and where in the brain may reside the anatomical correlates of such processes. In terms of general problem-solving capacity, one region, the prefrontal cortex, seems to be particularly important and is highly evolved in our species. In this chapter we also explore the probable role of social or Machiavellian intelligence in primate (and human) evolution, and the place of possible positive (altruism, empathy, reciprocity) as well as "negative" (exploitation, deceit, retaliation, manipulation, and plot) aspects in the evolution of social behaviors, social consciousness, and a "theory of mind"-aspects that may be singularly deficient in human autism. The need to be able to see things from another's point of view may have been crucial in the evolution of consciousness and of self-awareness, as may perhaps be indexed by an individual's responses to its own mirror reflection. Consciousness, however, like praxis, tool use, language, and intellect cannot be localized to a single structure or circuit, though certain networks undoubtedly play particularly important roles.