Much of this information has been touched on in other nodes, regardless, I will present reciprocal altruism as it applies to the biological sciences (also I felt the need to fill up this poor empty node).


  • The fundamental idea of reciprocal altruism is that animals may behave altruistically towards non-relatives if they have a high likelihood of receiving future aid in reward for their actions. See also: The Prisoner's Dilemma.

  • There are three necessary conditions for the evolution of reciprocal altruism to take place.

    1. Repeated pairwise interactions are needed to permit role exchanges between donor and beneficiary.
    2. The benefit of receiving aid must exceed the cost of donating.
    3. Donors must be able to recognize partners, remember their previous actions and refuse to cooperate with previous individuals that did not reciprocate.
  • What are the skills are necessary in a species to allow for the capacity of reciprocal altruism?
    1. The individuals of the species must be able to recognize, remember, and retaliate.
    2. Again, they must be able to benefit from the action, and this benefit must outweigh the potential cost of the altruistic action.
    3. The species in question must be reasonably social, i.e., there must be repeated social interactions between members of the species.

  • The biggest difference between traditional altruism and reciprocal altruism lies in the context of the supposedly altruistic action. According to traditional altruism, costly actions are more likely to performed for the benefit of a relative who shares genes with the performer. This is known as kin selection. Additionally, the performer's reproductive success may be increased if the altruistic action is successful. Even if the action is not successful, the relative's genes may be passed on. Reciprocal altruism is not dependent upon the genetics of the individuals involved.

  • Information is taken from Joan Strassmann's lecture on 11/01/00, entitled Reciprocal Altruism: Cooperation Between Animals. As of right now (12/02/04) you may find a copy of the lecture notes at this location: http://dacnet.rice.edu/courses/bios321/lectures/Class11Recipalthtml/sld001.htm

    Reciprocal altruism is the name given to the provision of goods and/or services by one organism to another, when the cost incurred by the donor in such provision will later (or sometimes, immediately) be repaid in the form of a reciprocated act—a returned favor, of sorts. By "cost" in the preceding sentence, I mean "cost to overall fitness for survival and/or reproduction." Reciprocal altruism is seen throughout the animal kingdom, most notably in human beings.

    In a landmark 1971 paper, titled "The Evolution of Reciprocal Altruism," purporting to reconcile altruism and evolution, Robert Trivers1 introduced the concept of reciprocal altruism to academia. He examined the ways in which altruistic acts can indirectly benefit the altruist herself, in the form of reciprocated behaviors—quid pro quo.

    Trivers' most detailed work is on reciprocal altruism in humans. He writes, "The strongest argument for the operation of reciprocal-altruistic selection in man is the psychological system controlling some forms of human altruism" (46). But he starts by giving several examples in other species, including fish and birds. In these examples, individual organisms use their faculty of identifying specific other individual organisms, to cultivate one-on-one relationships in which altruistic behaviors are reciprocated; favors are exchanged.

    Most intriguing is Trivers' reverse-engineering of the human moralistic emotions, examining several emotions and setting out an explanation of the evolutionary advantage there would be for an organism with the capacity for such an emotion, especially in light of that emotion's potential role in causing selectivity in altruistic behavior. Emotions like "liking," anger, jealousy, and so on, help to regulate the favor-exchange between humans, making sure that favors which are doled out are also repaid.

    Trivers' model is designed to show how certain classes of behavior denoted as "altruistic" can be selected for even when the recipient is so distantly related to the organism performing the altruistic act that another evolution-derived morality theory, kin selection, can be ruled out. The model of reciprocal altruism applies, for example, to altruistic behavior between members of different species (35).
    1. The "tri" is pronounced as in "trivia."

    Page numbers above refer to the Trivers paper itself. The complete citation for that paper is:
    Trivers, Robert L. "The Evolution of Reciprocal Altruism." The Quarterly Review of Biology 46:1 (Mar 1971), 35-57.

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