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5 - Drift

Published online by Cambridge University Press:  01 February 2024

Elliott Sober
Affiliation:
University of Wisconsin, Madison
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Summary

● Francis Galton helped invent a model that describes how family names can disappear from a population purely by chance; it provides a good entrée to the subject of neutral evolution. ● Strict neutrality needs to be distinguished from near neutrality. With strict neutrality, each token allele at a locus has a probability of 1/2N of eventually going to fixation if the population is diploid and contains N individuals; there is strict neutrality here because there is zero variation in fitness. ● The relationship of strict neutrality to the hypothesis of a molecular clock is clarified. ● Strict neutrality is a null hypothesis; the epistemic status of null hypotheses is discussed – are they default assumptions, to be viewed as innocent until proven guilty? ● Alternatives to the hypothesis of strict neutrality are discussed, including Tomoko Ohta’s theory of near neutrality, which says that nearly all genes are strictly neutral or slightly deleterious. ● Whether drift is a cause of evolution, and whether it is a process distinct from natural selection, are discussed, and so is the question of what it means for drift to be a stronger cause than selection in the evolution of an allele.

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Chapter
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The Philosophy of Evolutionary Theory
Concepts, Inferences, and Probabilities
, pp. 110 - 140
Publisher: Cambridge University Press
Print publication year: 2024

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  • Drift
  • Elliott Sober, University of Wisconsin, Madison
  • Book: The Philosophy of Evolutionary Theory
  • Online publication: 01 February 2024
  • Chapter DOI: https://doi.org/10.1017/9781009376037.006
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  • Drift
  • Elliott Sober, University of Wisconsin, Madison
  • Book: The Philosophy of Evolutionary Theory
  • Online publication: 01 February 2024
  • Chapter DOI: https://doi.org/10.1017/9781009376037.006
Available formats
×

Save book to Google Drive

To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.

  • Drift
  • Elliott Sober, University of Wisconsin, Madison
  • Book: The Philosophy of Evolutionary Theory
  • Online publication: 01 February 2024
  • Chapter DOI: https://doi.org/10.1017/9781009376037.006
Available formats
×