PubMed · 9104403
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C S Oliveira. [Moral conscience and nursing activities].. https://pubmed.ncbi.nlm.nih.gov/9104403/
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It is suggested that pathogen and parasite avoidance act as a driving force for kin selection. Preferential association with relatives decreases the probability of infection with unfamiliar pathogens. Altruistic behavior towards kin will further decrease the danger of infection by increasing the representation of relatives in a group. Such a behavioral strategy could evolve if pathogen resistance were heritable. Highly polymorphic major histocompatibility (MHC) genes largely determine heritable resistance to particular pathogens. The degree of relatedness within a group correlates with the degree of similarity in MHCs. It has been shown that detection of MHC type by mice guides preferential kin association. Pathogen avoidance appears to be the simplest explanation for the existence of a direct link between detecting the heritable component of the immune system and kin altruism. Detection of MHC also serves kin avoidance in mating. Periodic introduction of new genes including MHCs through mating provides resistance to the unavoidable appearance of foreign virulent pathogens (Hamilton et al., 1990, Proc. Natl Acad. Sci. U.S.A. 87, 3566-3573). It is suggested that kin preference favoring homogeneity punctuated by introduction of new genes through mating provides an optimal strategy for pathogen avoidance. Aggression might also serve to decrease infection by isolating or eliminating individuals with unrelated MHCs.
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Reciprocal altruism can become established among selfish, unrelated individuals if they use responsive strategies such as 'tit-for-tat. This result raises the fundamental question: how altruistic should one be? The problem is difficult to solve using current 'prisoner's dilemma' based models because they allow only the discrete choice of cooperating or defecting. In reality, however, cooperation is rarely all-or-nothing. Furthermore, if cooperative investment is variable, a new and more subtle kind of cheating becomes possible: individuals may invest slightly less than their partner. A concern is that this 'short-changing' will erode cooperative ventures. Here we show that cooperation can thrive despite variable investment through the new strategy of 'raise-the-stakes'. This strategy offers a small amount on first meeting and then, if matched, raises its investment, something that no strategy in the discrete model can do. We show that such behaviour can readily invade a population of non-altruists and cannot be effectively exploited. The practice of 'testing the water' rather than making sudden cooperative 'leaps of faith' powerfully reinforces the stability and effectiveness of reciprocity.