Group selection

From Academic Kids

In evolutionary biology, group selection refers to the idea that alleles can become fixed or spread in a population because of the benefits they bestow on groups, regardless of the fitness of individuals within that group.

Group selection was once a popular explanation for adaptations, especially by V.C. Wynne-Edwards. However, critiques, particularly by George C. Williams in his 1966 book Adaptation and Natural Selection, John Maynard Smith (1964) and C.M. Perrins (1964) cast serious doubt on group selection as a major mechanism of evolution. Some term this shift to a gene-centered view of evolution the "Williams revolution".

Overview

Theoretical models of the 1960s seemed to imply that the effect of group selection was negligible. Genetic variation, the raw material of selection, is much higher between individuals than it is between groups, particularly as groups grow larger. alleles are likely to be held on a population-wide level, leaving nothing for group selection to select for. In addition, most phenotypes, particularly physical ones, are not highly heritable in the first place. Additionally, generation time is much longer for groups than it is for individuals. Assuming conflicting selection pressures, individual selection will occur much faster, swamping any changes potentially favored by group selection. The Price equation can partition variance caused by natural selection at the individual level and the group level, and individual level selection causes greater effects.

Multilevel selection theory

In recent years, the limitations of earlier models have been addressed, and newer models suggest that selection may sometimes act above the gene level. Recently Elliot Sober and David Sloane Wilson have argued that the case against group selection has been overstated. They focus their argument on whether groups can have functional organization in the same way individuals do and, consequently, if groups can also be "vehicles" for selection. For example, groups that cooperate better may have out-reproduced those which did not. Resurrected in this way, Sober & Wilson's new group selection is usually called multilevel selection theory.

Although Richard Dawkins and fellow advocates of the gene-centered view of evolution remain unconvinced (see, for example, Cronk, 1994; Dawkins, 1994; Dennett, 1994), Sober and Wilson's work has been part of a broad revival of interest in multilevel selection as an explanation for evolutionary phenomena.

References

  • Dennett, D.C. (1994). E Pluribus Unum? Commentary on Wilson & Sober: Group Selection. Behavioural and Brain Sciences. 17 (4): 617-618. link (http://cogprints.ecs.soton.ac.uk/archive/00000281/00/wilsonso.htm)
  • Dawkins, R. (1994). Burying the Vehicle. Commentary on Wilson & Sober: Group Selection. Behavioural and Brain Sciences. 17 (4): 616-617. link (http://www.world-of-dawkins.com/Dawkins/Work/Articles/1994burying_the_vehicle.htm)
  • Hamilton, W.D. (1964) The evolution of social behavior Journal of Theoretical Biology 1:295311
  • Maynard Smith, J. (1964) Group selection and kin selection Nature 201:1145-1147
  • Wynne-Edwards, V.C. (1962). Animal Dispersion in Relation to Social Behaviour. Edinburgh: Oliver & Boyd.
  • Wynne-Edwards, V. C. (1986) Evolution Through Group Selection, Oxford ISBN
  • Williams, G.C. (1966) Adaptation and Natural Selection
  • Williams, G.C. (1971) (ed) Group Selection
  • Wilson, D.S. & Sober, E. 1994. Reintroducing group selection to the human behavioral sciences. Behavioral and Brain Sciences 17 (4): 585-654. link (http://www.bbsonline.org/documents/a/00/00/04/60/bbs00000460-00/bbs.wilson.html)
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