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Bias in the Introduction of Variation as an Orienting Factor in Evolution



L Y. Yampolsky, Arlin Stoltzfus


According to New Synthesis doctrine, the direction of evolution is determined by selection and not by internal causes that act by way of propensities of variation. This doctrine rests on the theoretical claim that because mutation rates are small in comparison to selection coefficients, mutation is powerless to overcome opposing selection. Using a simple population-genetic model, this claim is shown to depend on assuming the prior availability of variation, so that mutation may act only as a pressure on the frequencies of existing alleles, and not as the evolutionary process that introduces novelty. As shown here, mutational bias in the introduction of novelty can strongly influence the course of evolution, even when mutation rates are small in comparison to selection coefficients. Recognizing this mode of causation provides a distinct mechanistic basis for an internalist approach to determining the contribution of mutational and developmental factors to evolutionary phenomena such as homoplasy, parallelism, and directionality.
Evolution and Development
No. 2


development, evolution, mutation bias, population genetics


Yampolsky, L. and Stoltzfus, A. (2001), Bias in the Introduction of Variation as an Orienting Factor in Evolution, Evolution and Development (Accessed July 13, 2024)


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Created December 31, 2000, Updated October 12, 2021