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HAMILTON'S RULE Formally, such genes should increase in frequency when : where R B C This equation is known as Hamilton's rule after W. D. Hamilton who published, in 1964, the first formal quantitative treatment of kin selection to deal with the Evolution of apparently altruistic acts. The phrase '''Kin selection''', however, was coined by John Maynard Smith . Technically, the correct definition for relatedness (''R'') in Hamilton's rule describes it as a Regression measure. Regressions, unlike probabilities, can be negative, and so it is possible for individuals to be negatively related, which simply means that two individuals can be less genetically alike than two random ones on average. This has been invoked to explain the evolution of Spite ful behaviours. In the 1930s J.B.S. Haldane had full grasp of the basic quantities and considerations that play a role in kin selection. He famously said that, "I'd lay down my life for two brothers or eight Cousins ". Kin altruism is the term for altruistic behaviour whose evolution is supposed to have been driven by kin selection. However, recently, B.J. Williams showed that, when mating pairs are rigidly monogamous so that altruistic acts lower the fitness of both spouses, it is much harder for altruism to evolve unless reproductive rates are very high. However, rigid monogamy is uncommon in nature. Haldane's remark alluded to the fact that if an individual loses its life to save two siblings, four nephews, or eight cousins, it is a "fair deal" in evolutionary terms, as siblings are on average 50% identical by descent, nephews 25%, and cousins 12.5% (in a Diploid population that is randomly mating and previously Outbred ). But Haldane also joked that he would truly die only to save more than one identical twins or more than two full siblings. The concept of kin selection was first invoked by Darwin as an explanation of the sterile Caste s of Social Insect s. In Chapter 8 of '' The Origin Of Species '' he wrote about a "special difficulty, which at first appeared to me insuperable, and actually fatal to my whole theory. I allude to the neuters or sterile females in insect-communities: for these neuters often differ widely in instinct and in structure from both the males and fertile females, and yet, from being sterile, they cannot propagate their kind." He continued: "...This difficulty, though appearing insuperable, is lessened, or, as I believe, disappears, when it is remembered that selection may be applied to the family, as well as to the individual, and may thus gain the desired end." MECHANISM For kin-selection, individuals must behave nepotistically (i.e., favor their kin). Often this involves recognizing kin by innate reactions to traits which signal relatedness or to imprinted features which distinguish the individuals one grew up with (which are more likely to be kin). But Nepotism need not be purely altruistic nor involve kin recognition. For instance, Tiger Salamander s produce a non-cannibalistic larval morph that cannot prey on salamander eggs and other young salamanders. This reduces the damage the larvae inflict on each other and thus on their own kin. This morph switch is kin-imprinted as the cannibalistic morph is triggered when the eggs develop in presence of non-biological kin. However, non-cannibalism protects all eggs and young salamanders in a pond rather than only those of the same kin. Kin selection has been invoked to explain the evolution of social Insect s such as Ant s and Termite s, of Multicellularity , and even of humanity's social structure. However, the role of kin selection in human social systems is disputed. SEE ALSO REFERENCES | ||
| Year | 1999 |
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| Title | '''Psychologically Speaking: A Book of Quotations''' |
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| Chapter | Altruism |
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| Editor | Kevin Connolly and Maragaret Martlew |
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| Pages | 10 |
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| Publisher | BPS Books |
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| Id | ISBN 185433302X |
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