Selection of parentèle
The theory of the selection of parentèle (or Kin selection , in English) was first once advanced by Darwin like an explanation to the existence of the sterile workers in the social insects like the ants. Indeed, the presence of such individuals unable to transmit copies of their own genes to their descendants was in contradiction with the Théorie of the evolution. Darwin outlined a solution with this paradox by proposing as the selection applies as well to the family as with the individual.
This solution was formulated within a mathematical framework by the biologist William Donald Hamilton. This theory stipulates that individuals can transmit copies of their own genes not only while reproducing, but also by supporting the reproduction of connected individuals, for example of the sisters, the brothers or the cousins by a behavior Altruiste. It leaves the principle which the ants have a very great number of joint genes. That the brother of an ant or the ant itself thus reproduces, returns to same and explains how the altruism could be spread.
The mathematical formalization of this idea is given by the rule of Hamilton , the transmission of a characteristic will be favoured if:
where
- R = is the coefficient of political alliance ( coefficient off relatedeness )
- B = is increase in the selective value of the individual profiting from an altruistic act.
- C = is the cost of the selective value of the individual who produces the altruistic act.
- B = is increase in the selective value of the individual profiting from an altruistic act.
R is the proportion of the genes of an individual has which are common by ascent (thus identical) to genes present at B. In a nonconsanguineous population one checks easily that the coefficient of political alliance between identical twin is of 1, between brothers and sisters 1/2, two half-brothers 1/4, first cousins 1/8, etc
One of the weaknesses of this model resides in the fact that R is often very weak and that the output of an altruistic act must then be extremely high to be profitable. Under the natural conditions this uncertainty seems to limit its application largely.
See too
References
- Hamilton, W.D. (1964). The genetical evolution off social behavior I and II. - Newspaper off Theoretical Biology 7 : 1-16 and 17-52. pubmed I pubmed II
- Lucas, J.R., Creel, S.R. & Waser, TOKEN ENTRY (1996) How to inclusive measure fitness, revisited, Animal Behavior , 51 , 225-228.
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