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driftDrift (ger.)

  • 1) Change in gene frequencies.

    It is the idlers that make the crowd; and very slight [selective] attractions may determine their drift

    Fisher, R.A. (1929).The evolution of dominance; reply to Professor Sewall Wright. Amer. Nat. 63, 553-6: 556.


    natural selection plays with much greater force on the heterozygotes […] [resulting in] a gradual drift of the heterozygote toward the wild type

    Wright, S. (1929). Fisher’s theory of dominance. American Naturalist 63, 274-9: 274.

  • 2) Random fluctuation in gene frequencies, especially in a small breeding populations, considered as an evolutionary force opposed to natural selection.

    those genes which are not controlled by moderately strong selections would ordinarily drift at random through the multiple dimensionsonal system of gene frequencies

    Wright, S. (1929). The evolution of dominance. Comment on Dr. Fisher’s reply. Amer. Nat. 63, 556-61: 561.


    the effects of random sampling of gametes in each generation brings about a random drifting of gene frequencies about their mean positions of equilibrium.

    Wright, S. (1930). The genetical theory of natural selection. A review. J. Heredity 21, 349-56: 354.

    random drifting of gene frequencies
    Wright, S. (1931). Evolution in Mendelian populations. Genetics 16, 97-159: 151.

    The processes of the genetic drift and of selection are […] pitted against each other, and the outcome in any one population depends upon the relative strength of the opposing forces

    Dobzhansky, T. (1937/41). Genetics and the Origin of Species: 332; cf. 185; 332.


    The phenomenon of "genetic drift" will come into play. There will be a random loss and fixation of genes resulting from the errors of sampling of the gametes which reproduce each generation, largely without regard to the adaptive value of the genes involved. As a result, the fate of an organism which is too greatly restricted in numbers is extinction.

    Erickson, R.O. (1945). The Clematis fremontii Var. Riehlii population in the Ozarks. Annals of the Missouri Botanical Garden 32, 413-60: 414.

    The directed processes may described as producing a cumulative steady drift in gene frequency, complementing the term random drift that has been used for the cumulative effects of the random processes.
    Wright, S. (1955). Classification of the factors of evolution. Cold Spring Harbor Symp. Quant. Biol. 20, 16-24: 18.

    from a position of omniscience, there is no need for the notion of drift; evolution simply moves faster among small populations, when their gene frequencies change at all

    Rosenberg, A. (1994). Instrumental Biology or the Disunity of Science: 73.


    drift is better though of as the expected statistical scatter around the mean predictive fitness

    Pigliucci, M. & Kaplan, J. (2006). Making Sense of Evolution. The Conceptual Foundations of Evolutionary Biology: 33.