Fisher's fundamental theorem of natural selection is an idea about
genetic variance in
population genetics
Population genetics is a subfield of genetics that deals with genetic differences within and between populations, and is a part of evolutionary biology. Studies in this branch of biology examine such phenomena as Adaptation (biology), adaptation, ...
developed by the
statistician and
evolutionary biologist
Evolutionary biology is the subfield of biology that studies the evolutionary processes (natural selection, common descent, speciation) that produced the diversity of life on Earth. It is also defined as the study of the history of life for ...
Ronald Fisher
Sir Ronald Aylmer Fisher (17 February 1890 – 29 July 1962) was a British polymath who was active as a mathematician, statistician, biologist, geneticist, and academic. For his work in statistics, he has been described as "a genius who ...
. The proper way of applying the abstract mathematics of the theorem to actual biology has been a matter of some debate.
It states:
:"The rate of increase in
fitness of any
organism
In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and ...
at any time is equal to its genetic variance in fitness at that time."
Or in more modern terminology:
:"The rate of increase in the mean fitness of any organism, at any time, that is ascribable to natural selection acting through changes in
gene frequencies, is exactly equal to its genetic variance in fitness at that time".
History
The theorem was first formulated in Fisher's 1930 book ''
The Genetical Theory of Natural Selection
''The Genetical Theory of Natural Selection'' is a book by Ronald Fisher which combines Mendelian genetics with Charles Darwin's theory of natural selection, with Fisher being the first to argue that "Mendelism therefore validates Darwinism" and ...
''.
[ Fisher likened it to the law of entropy in ]physics
Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which r ...
, stating that "It is not a little instructive that so similar a law should hold the supreme position among the biological sciences". The model of quasi-linkage equilibrium was introduced by Motoo Kimura
(November 13, 1924 – November 13, 1994) was a Japanese biologist best known for introducing the neutral theory of molecular evolution in 1968. He became one of the most influential theoretical population geneticists. He is remembered in genet ...
in 1965 as an approximation in the case of weak selection and weak epistasis.Sewall Wright
Sewall Green Wright FRS(For) Honorary FRSE (December 21, 1889March 3, 1988) was an American geneticist known for his influential work on evolutionary theory and also for his work on path analysis. He was a founder of population genetics alongsi ...
about adaptive landscapes, the theorem was widely misunderstood to mean that the average fitness of a population would always increase, even though models showed this not to be the case.
References
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External links
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{{Population genetics
Population genetics
Biological theorems
Evolutionary dynamics
Modern synthesis (20th century)