The neutral theory of molecular evolution states that the vast majority of evolutionary changes at the molecular level are caused by random drift of selectively neutral mutants (not affecting fitness). The theory was introduced by Motoo Kimura in the late 1960s and early 1970s. Neutral theory is compatible with Darwin's theory of evolution by natural selection: adaptive changes are acknowledged as present and important, but hypothesized to be a small minority of all the changes seen fixed in DNA sequences. Since then, this hypothesis has been tested using the McDonald-Kreitman test, and has not been supported in all species. Even in those species in which adaptive changes are rare, background selection at linked sites may violate neutral theory's assumptions regarding genetic drift.
Read more about Neutral Theory Of Molecular Evolution: Overview, The "neutralist–selectionist" Debate
Famous quotes containing the words neutral, theory and/or evolution:
“The lonely Earth amid the balls
That hurry through the eternal halls,
A makeweight flying to the void,
Supplemental asteroid,
Or compensatory spark,
Shoots across the neutral Dark.”
—Ralph Waldo Emerson (1803–1882)
“Everything to which we concede existence is a posit from the standpoint of a description of the theory-building process, and simultaneously real from the standpoint of the theory that is being built. Nor let us look down on the standpoint of the theory as make-believe; for we can never do better than occupy the standpoint of some theory or other, the best we can muster at the time.”
—Willard Van Orman Quine (b. 1908)
“By contrast with history, evolution is an unconscious process. Another, and perhaps a better way of putting it would be to say that evolution is a natural process, history a human one.... Insofar as we treat man as a part of nature—for instance in a biological survey of evolution—we are precisely not treating him as a historical being. As a historically developing being, he is set over against nature, both as a knower and as a doer.”
—Owen Barfield (b. 1898)