Neutral theory of molecular evolution

The neutral theory of molecular evolution holds that most <a href="/facts/Evolutionary/TuWap5IK">evolutionary</a> changes occur at the molecular level, and most of the variation within and between species are due to random <a href="/facts/Genetic_drift/lvoEEctX">genetic drift</a> of <a href="/facts/Mutation/Ee4NnWbY">mutant</a> <a href="/facts/Allele/8FxCS9KA">alleles</a> that are selectively <a href="/facts/Neutral_mutation/juuaNJ8T">neutral</a>. The theory applies only for evolution at the molecular level, and is compatible with <a href="/facts/Phenotype/vxWXKGLj">phenotypic</a> evolution being shaped by <a href="/facts/Natural_selection/JXTte6en">natural selection</a> as postulated by <a href="/facts/Charles_Darwin/uwDLGItY">Charles Darwin</a>.
The neutral theory allows for the possibility that most mutations are deleterious, but holds that because these are rapidly removed by <a href="/facts/Purifying_selection/DCkRLqb4">natural selection</a>, they do not make significant contributions to variation within and between <a href="/facts/Species/oDg6b96r">species</a> at the molecular level. A <a href="/facts/Neutral_mutation/juuaNJ8T">neutral mutation</a> is one that does not affect an organism's ability to survive and reproduce.
The neutral theory assumes that most mutations that are not deleterious are neutral rather than beneficial. Because only a fraction of <a href="/facts/Gamete/j8e8fls6">gametes</a> are sampled in each generation of a species, the neutral theory suggests that a mutant allele can arise within a population and reach <a href="/facts/Fixation_(population_genetics)/wDJzlUq7">fixation</a> by chance, rather than by selective advantage.
The theory was introduced by the Japanese biologist <a href="/facts/Motoo_Kimura/9682hIVP">Motoo Kimura</a> in 1968, and independently by two American biologists <a href="/facts/Jack_Lester_King/MErF22Gc">Jack Lester King</a> and <a href="/facts/Thomas_H._Jukes/RYlQ5GTu">Thomas Hughes Jukes</a> in 1969, and described in detail by Kimura in his 1983 monograph <a href="/facts/The_Neutral_Theory_of_Molecular_Evolution/ShVENb2K">The Neutral Theory of Molecular Evolution</a>. The proposal of the neutral theory was followed by an extensive "neutralist–selectionist" controversy over the interpretation of patterns of molecular divergence and <a href="/facts/Gene_polymorphism/6U9NzHwH">gene polymorphism</a>, peaking in the 1970s and 1980s.
Neutral theory is frequently used as the <a href="/facts/Null_hypothesis/C8NwSE9J">null hypothesis</a>, as opposed to <a href="/facts/Adaptive/pNhTC1EB">adaptive</a> explanations, for describing the emergence of morphological or genetic features in organisms and populations. This has been suggested in a number of areas, including in explaining genetic variation between populations of one nominal species, the emergence of complex subcellular machinery, and the convergent emergence of several typical microbial morphologies.

Neutral theory of molecular evolution open-in-new

Neutral theory of molecular evolution