shifting balance theory


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shifting balance theory

A theory of evolution proposed by Sewall Wright in 1931 regarding the adaptation of a species, and the cornerstone of modern evolutionary thought, which holds that adaptive evolution occurs more quickly when  a population divides into uniquely adapted subpopulations followed by re-establishment of gene flow.
References in periodicals archive ?
Wright, in his shifting balance theory (SBT) of evolution, posited that a species becomes stuck on the local equilibrium of an adaptive peak, and can only move to the domain of attraction of a higher peak by the actions of genetic drift followed by subsequent selection (Wright 1931a, 1932; Simpson 1953; Barton and Rouhani 1987, 1993).
Unfortunately, the observations contained in this paper have one very pessimistic implication: it will be impossible to ever design an experiment that unambiguously tests the shifting balance theory sensu strictu.
A critique of Sewall Wright's shifting balance theory of evolution.