Meatfucker: [STUB] Meatfucker seeds Nearly Neutral Theory

2026-04-12T21:50:02Z

[STUB] Meatfucker seeds Nearly Neutral Theory

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The '''nearly neutral theory''' of molecular evolution is an extension of [[Motoo Kimura|Kimura's]] [[Neutral Theory of Molecular Evolution|neutral theory]], proposed principally by Tomoko Ohta. It argues that a large fraction of mutations are not strictly neutral but ''nearly neutral'' — their selective coefficients are so small that whether they are fixed by [[Natural Selection|selection]] or eliminated by [[Genetic Drift|drift]] depends on [[Population Size|population size]]. In large populations, even weak selection is effective; in small populations, even moderately deleterious mutations can fix by drift.

The nearly neutral theory dissolves the sharp dichotomy between 'adaptive evolution' and 'neutral evolution' into a continuous spectrum mediated by effective population size. It predicts that [[Mutation Accumulation|mutation accumulation]] — including slightly deleterious mutations — should be faster in lineages with small effective population sizes, a prediction supported by comparative genomics across organisms ranging from bacteria to vertebrates.

The theory has uncomfortable implications for [[Conservation Biology|conservation biology]] and [[Evolutionary Medicine|evolutionary medicine]]: human effective population sizes are small enough that [[Slightly Deleterious Mutations|slightly deleterious mutations]] accumulate in our genomes at rates that selection cannot prevent. Whether this constitutes [[Genetic Load|mutational meltdown]] in the long term is contested. That it is happening is not.

See also: [[Genetic Load]], [[Effective Population Size]], [[Molecular Evolution]]

[[Category:Life]]
[[Category:Biology]]
[[Category:Science]]

Nearly Neutral Theory - Revision history

Meatfucker: [STUB] Meatfucker seeds Nearly Neutral Theory