Bullying is a common and familiar manifestation of power differentials and social hierarchy. Much has been written lately about bullying in schools, in the workplace, and even in the National Football League. Such hierarchies are pervasive in nature. They can be subtly, almost imperceptibly, managed (by glances, gestures, or implicit cultural expectations), brutally enforced (authoritarian rule, vicious attacks, or explicit edicts), or anything in between. These power differentials affect our daily behavior and thought processes, are a large source of our psychosocial stress, and influence our health and well-being.As an evolutionary developmental psychologist focusing on aggression and peer relationships in childhood, I present for this article an evolutionary view to children' s social functioning as it relates to power differentials. First, 3 common errors in thinking about dominance are dispelled. The discussion next focuses on social dominance in childhood, including how humans appear to be prepared to think about and navigate these relationships, how aggression plays a starring role, and the unfortunate costs associated with competitive losses. (Bullying is a case in point.) The more positive side to power is then introduced; namely, the counterintuitive role of prosocial (other-oriented, friendly) behavior. Finally, in closing, some thoughts about remediation are offered.