genetic drift

Compiled with AI assistance and selectively reviewed. Please consult the cited passages; the books remain the authoritative source. About this companion

Editorial synthesis · provisional

Definition

Genetic drift is stochastic change in allele representation and fixation in populations, distinguished here from positive selection for advantageous traits. RB1 uses Kimura’s neutral model to explain how neutral mutations can become molecular substitutions. Drift contributes to evolutionary history without supplying a predetermined direction, and its role does not mean that all change is neutral, that selection disappears or that genetic and linguistic drift are identical processes.

Explanation

The source places neutral theory within standard population genetics, alongside population subdivision, mating structure and genetic load. Kimura’s specific emphasis is neutral substitution through fixation by drift. The proposed entry retains that domain and attribution without equating every observed change in a population with adaptive improvement.

RB1’s overview explicitly says neutral theory adds an explanatory layer rather than discarding selection. Its variation discussion also allows drift to contribute to divergence in isolated populations. A stochastic contribution and a selective contribution can thus coexist without being reduced to one mechanism or made rival descriptions of every event.

The later comparison table lists drift among biological amplification routes, whereas language has its own transmission and adoption processes. AB also distinguishes purposeful cultural inheritance from biological inheritance. These contexts support a disciplined comparison of historical contingency, not a claim that allele frequencies, word meanings and random physical motion are one quantity.

Scope and attribution

Preserve the population-genetic scope and named neutral-theory emphasis without adding an absent quantitative model.

RB1 — The Real Book, Volume I: The Possible Is Real

Kimura’s neutral fixation account is placed alongside retained selection and population structure.

Occurrence locators: 150, 151, 154, 170, 187, 188.

Background used in the editorial explanation

Named theories and mechanisms are distinguished from neighboring background, homonyms and the author’s own synthesis. Reproduced AI passages retain their separate voice.