of within-group contest interactions. In the yellow baboon, adult females form relationships with their kin, who offer support during times of violent conflict within social groups. In Barbary macaques, social grooming results in the formation of crucial relationships among partners. These social relationships serve to aid cooperation and facilitate protection against combative groups composed of other males, which can oftentimes cause physical harm. Furthermore, social relationships have also been proven to decrease risk of infanticide in several primates. Altruism Altruism, in the biological sense, refers to a behavior performed by an individual that increases the fitness of another individual while decreasing the fitness of the one performing the behavior. This differs from the philosophical concept of altruism which requires the conscious intention of helping another. As a behavior, altruism is not evaluated in moral terms, but rather as a consequence of an action for reproductive fitness. It is often questioned why the behavior persists if it is costly to the one performing it, however, Charles Darwin proposed group selection as the mechanism behind the clear advantages of altruism. Social grooming is considered a behavior of facultative altruism- the behavior itself is a temporary loss of direct fitness (with potential for indirect fitness gain), followed by personal reproduction. This tradeoff has been compared to the Prisoner's Dilemma model, and out of this comparison came Robert Trivers reciprocal altruism theory under the title "tit-for-tat". In conjunction with altruism, kin selection bears an emphasis on favoring the reproductive success of an organism's relatives, even at a cost to the organism's own survival and reproduction. Because of this, kin selection is an instance of inclusive fitness, which combines the number of offspring produced with the number an individual can ensure the production of by supporting others, such as siblings. Hamilton's rule Developed by W.D. Hamilton, this rule governs the idea that kin selection causes genes to increase in frequency when the genetic relatedness (r) of a recipient to an actor multiplied by the benefit to the recipient (B) is greater than the reproductive cost to the actor (C). Thus, it is advantageous for an individual to partake in altruistic behaviors, such as social grooming, so long as the individual receiving the benefits of the behavior is related to the one providing the behavior. Use as a commodity It was questioned whether some animals are instead using altruistic behaviors as a market strategy to trade