Motoo Kimura

Japanese geneticist

Written by

The Information Architects of Encyclopaedia Britannica

Last updated

July 1, 2026

Quick Summary

Motoo Kimura was a Japanese geneticist who proposed the neutrality theory of molecular evolution in 1968. This theory suggests that many evolutionary changes at the molecular level, such as in DNA and protein sequences, are selectively neutral. This means these changes have little to no impact on an organism's fitness and their frequency changes primarily due to genetic drift rather than natural selection. If the neutrality theory is correct, it provides a basis for the molecular clock hypothesis, suggesting that the rate of molecular change can estimate the time since species diverged. While the molecular clock isn't exact, Kimura's work significantly advanced the study of evolutionary history through molecular data.123

Summary created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

3 Britannica Sources

Ask Britannica AI about this topic

Britannica doesn't have a full article on this topic, so we've curated a list of our relevant coverage.

evolution
Molecular biology and Earth sciences
In 1968 the Japanese geneticist Motoo Kimura proposed the neutrality theory of molecular evolution, which assumes that, at the level of the sequences of nucleotides in DNA and of amino acids in proteins, many changes are adaptively neutral; they have little or no effect on the molecule’s function and thus…
Read More
In 1968 the Japanese geneticist Motoo Kimura proposed the neutrality theory of molecular evolution, which assumes that, at the level of the sequences of nucleotides in DNA and of amino acids in proteins, many changes are adaptively neutral; they have little or no effect on the molecule’s function and thus…
Read More