"Contrary to conventional wisdom, McCullough contends that the desire for revenge should not be likened to a "disease" or a "poison" that makes people do terrible things to each other. Instead, he argues, natural selection created our penchant for revenge because it helped our ancestors solve social dilemmas they encountered during human evolution. Revenge, according to McCullough, is a "problem" for us today because "it was a "solution" during our ancestral past. McCullough also debunks the misconception that forgiveness should be likened to an "antidote" or a "cure" for the desire for revenge. Instead, he argues, humans' capacity to forgive evolved because it helped our ancestors preserve relationships with genetic relatives and other valuable relationship partners. McCullough goes on to argue that when we encounter the social circumstances that activated the "forgiveness instinct" in the ancestral past, modern-day humans will be naturally inclined to forgive, often with less effort than we usually assume."--Book jacket.