The nearly neutral theory of molecular evolution is a modification of the neutral theory of molecular evolution that accounts for slightly advantageous or deleterious mutations at the molecular level. The nearly neutral theory was proposed by Tomoko Ohta in 1973 (including only deleterious mutations) and expanded in the early 1990s to include both advantageous and deleterious nearly neutral mutations. Unlike in Motoo Kimura's original neutral theory—which dealt only with mutations unaffected by natural selection—the nearly neutral theory predicts a relationship between population size and the rate of molecular evolution: in larger populations, genetic drift, which can bring even slightly deleterious mutations to fixation, is a weaker force, so evolution happens more slowly than in smaller populations.
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Famous quotes containing the words neutral, theory and/or evolution:
“The seashore is a sort of neutral ground, a most advantageous point from which to contemplate this world. It is even a trivial place. The waves forever rolling to the land are too far-traveled and untamable to be familiar. Creeping along the endless beach amid the sun-squall and the foam, it occurs to us that we, too, are the product of sea-slime.”
—Henry David Thoreau (1817–1862)
“Every theory is a self-fulfilling prophecy that orders experience into the framework it provides.”
—Ruth Hubbard (b. 1924)
“As a natural process, of the same character as the development of a tree from its seed, or of a fowl from its egg, evolution excludes creation and all other kinds of supernatural intervention.”
—Thomas Henry Huxley (1825–95)