This chapter deals with language and natural selection. One of the most striking differences between language and the communication of animals is the difference in their relationship to fitness. All units of all animal communication systems were originally selected for, and continue to exist because, expression of those units under the appropriate circumstances confers inclusive fitness. Language as a whole may appear adaptive in the long run, and at any rate, the one species possessing it has achieved a position of unparalleled dominance in nature, but it is too large and vague a category for statements like language increases fitness or language is adaptive to have much sense. One might almost as well say communication increases fitness or behavior is adaptive. The complexity of primate social relations, which initially seemed to favor social intelligence pressures, turns out on closer examination to do the very opposite.