This chapter uses the adaptationist program (Williams, 1966) - to predict and explain the major features of anger. According to this approach, anger evolved by natural selection to bargain for better treatment. Thus, the major triggers of anger (e.g. cost impositions, cues of disrespect) all indicate an increased willingness (on the part of the offender) to impose costs on the angry individual. Once triggered, the anger system bargains using the two primary incentives that humans have available to modify others’ behavior in favor of the focal individual: the imposition of costs and the denial of benefits. This simple functional sketch of anger is then supplemented with additional considerations needed to address the resultant selection pressures created by bargaining. This process offers functionally sound and theoretically justified explanations for: anger in aggressive and cooperative contexts, the role of apologies and their sincerity, the content of sex-specific insults, the computational structure of “intentionality” in the context of anger, and the origin of the implicit rules of combat.