Our website is made possible by displaying online advertisements to our visitors.
Please consider supporting us by disabling your ad blocker.

Responsive image


Fisher's principle

Fisher's principle is an evolutionary model that explains why the sex ratio of most species that produce offspring through sexual reproduction is approximately 1:1 between males and females. A. W. F. Edwards has remarked that it is "probably the most celebrated argument in evolutionary biology".[1]

Fisher's principle was outlined by Ronald Fisher in his 1930 book The Genetical Theory of Natural Selection[2] (but has been incorrectly attributed as original to Fisher[1]). Fisher couched his argument in terms of parental expenditure, and predicted that parental expenditure on both sexes should be equal. Sex ratios that are 1:1 are hence known as "Fisherian", and those that are not 1:1 are "non-Fisherian" or "extraordinary" and occur because they break the assumptions made in Fisher's model.[3][4]

  1. ^ a b Cite error: The named reference Edwards98 was invoked but never defined (see the help page).
  2. ^ Cite error: The named reference Fisher30 was invoked but never defined (see the help page).
  3. ^ Cite error: The named reference Hamilton67 was invoked but never defined (see the help page).
  4. ^ Charnov, E., and Bull, J. (1989). "Non-fisherian sex ratios with sex change and environmental sex determination", Nature 338, pp. 148–150. https://doi.org/10.1038/338148a0 Retrieved 29 March 2022.

Previous Page Next Page