Kin selection
The kin selection (English kin selection, kin selection also ) is an extension of the concept of natural selection and is used in evolutionary biology and sociobiology. As part of overall fitness theory it explains the inheritance of cooperative and " altruistic " behavior. If animals relatives help raise their young, this promotes the dissemination of their "own" genetic material. The extent of altruistic behavior depends on the degree of kinship. The closer animals are related to each other, the higher the probability by relatives Help "own" genes to pass on to the next generation and more frequent altruistic behavior is encountered. The theory of kin selection was developed by John Maynard Smith ( 1964) and William D. Hamilton.
Total Fitness
Total Fitness = direct indirect fitness Fitness
The overall genetic fitness (English " inclusive fitness" ), the genetic success of a living being, is measured by the number of own genes that are present in the next generation. It is composed of the direct fitness, the number of genes that is passed on by their own offspring, and the indirect fitness, the number of one's genes that is passed on relatives to the next generation. An individual that increases the reproductive chances of a close relative, may thus an increase in its own inclusive fitness effect (ie, genetic success).
This altruism is only successful and spreads in populations, if the benefit to the Genweitergabe that shows the altruistic behavior is greater than the costs which are applied for ( Hamilton's rule).
In mathematical terms, the ratio of benefit (B ) to cost (C ) must be greater than 1 divided by the degree of relationship.
Here, B is the benefit ( benefit ), C is the cost (cost ) and r is the coefficient of kinship ( relatedness ).
Including the various degrees of relationship to the recipient and to their own offspring in the following formula (Hamilton 's rule ):
Where the degree of relationship of the encoder to the descendants of the recipient and relationship of the encoder to its own offspring is.
Examples
Example 1: An animal that gives up two of his own offspring (C = 2), but a sibling ( degree of relationship between brothers and sisters in diploid organisms r = 0.5) helps to get five additional offspring (B = 5), has a higher overall fitness as an animal that is " selfish" does not help.
Example 2: Many workers in insects nations renounce their own offspring and to sacrifice for the defense of the people, even their lives. The kin selection is a plausible explanation for it. Because of the unusual Haplodiploidie hymenopterer social insects ( ants, bees and wasps ) results at full sisters of a nest relationship a coefficient of 0.75 on average, with their full brothers 0.25. With their own offspring but these workers are only 50% (r = 0.5), less than with her sisters, related. As a result, it is genetically advantageous raise their own sisters for workers social Hymenoptera instead get yourself daughters.
Example 3: If a man sacrifices his life, but survive for two siblings, that makes no difference for his genes; he rescues three siblings, which is a win for his genes. From the perspective of overall fitness, a person should sacrifice their lives, if they thereby more than two of their children, four nephews or cousins eight saves as a child 50 %, 25%, and a nephew, a cousin has 12.5 % of the genes in common with her.
Group structure
The kin selection also makes statements about group structure of populations. When is an unequal hierarchy is emerging, in which to breed only the highest ranking? Should be to maximize its inclusive fitness the individual to focus on increasing the direct fitness or increasing the indirect fitness depending on the environmental conditions.
If the environmental conditions are favorable and the potential reproductive success of large, then an individual should migrate and spread his genes through their own offspring. The hierarchy differences within a group are then low.
Are the environmental conditions unfavorable and the potential reproductive success low, then the individual should stay at home. Are then formed hierarchical group structures out with a strong hierarchy.
Criticism of the approach of kin selection
The American entomologist and biologist Edward O. Wilson Socio, who introduced the term sociobiology is temporarily moved away from the overall fitness theory and kin selection as the basis of sociobiology, 2012, he criticized this approach even as unscientific. Next he says about this foundation of sociobiology:
" The old paradigm of social evolution, which enjoys almost holy status after four decades, failed. His reasoning of kin selection as a process on Hamilton's inequality as a condition for cooperation to overall fitness as Darwinian status of colony members is not working. If it ever comes to kin selection in animals, it is only in a weak form of selection that occurs only under special conditions easily injured. As the subject of a general theory of inclusive fitness is a false mathematical construct; Under no circumstances it can be so believe that it gets real biological significance. Also for the enactment of the evolution dynamics of genetic social systems, it is useless. "
Competing / advanced concepts
- Group selection 1962 Vero Wynne -Edwards
- Reciprocal altruism, Tit for Tat; Robert L. Trivers
- Optimal skew theory, Laurent Keller, H. Kern Reeve
- A mathematically elegant synthesis of kin selection (or more generally of individual selection, taking into account genetic affinities ) and of group selection is the Price equation, are considered in the individual as well as group selection.