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Reciprocal altruism is a form of altruism in which one organism provides a benefit to another, often at a cost to itself, in the expectation of future reciprocation. This behavior is found among humans in many forms: friendship, adult-child relationships, etc. There is controversy as to whether great apes exhibit reciprocal altruism. It may be seen when a dominant chimpanzee male allows another male to mate with a female in hopes of receiving support in the future.