Nearly neutral theory of molecular evolution¶

The nearly neutral theory of molecular evolution is a modification of the neutral theory of molecular evolution that accounts for the fact that not all mutations are either so deleterious such that they can be ignored, or else neutral.

Version: v1 · 2026-09-28 · History
Domain-specific #: 10933
Domain group: Natural Sciences
Origin domain: Biology & Ecology
Subdomains: Molecular Evolution, Population Genetics → Biology & Ecology

Core Idea¶

Nearly neutral theory of molecular evolution is treated here as the recurring natural_sciences_engineering_health identity summarized by this source-grounded definition: The nearly neutral theory of molecular evolution is a modification of the neutral theory of molecular evolution that accounts for the fact that not all mutations are either so deleterious such that they can be ignored, or else neutral.

The nearly neutral theory of molecular evolution is a modification of the neutral theory of molecular evolution that accounts for the fact that not all mutations are either so deleterious such that they can be ignored, or else neutral. Slightly deleterious mutations are reliably purged only when their selection coefficient are greater than one divided by the effective population size. In larger populations, a higher proportion of mutations exceed this threshold for which genetic drift cannot overpower selection, leading to fewer fixation events and so slower molecular evolution.

The nearly neutral theory was proposed by Tomoko Ohta in 1973. The population-size-dependent threshold for purging mutations has been called the "drift barrier" by Michael Lynch, and used to explain differences in genomic architecture among species. If nearly neutral mutations are common, then the proportion for which P_{fix} \ll \frac{1}{N_e} is dependent on N_e.

For Nearly neutral theory of molecular evolution, the abstraction is narrower than the article's general subject matter: a positive case must preserve The nearly neutral theory of molecular evolution is a modification of the neutral theory of molecular evolution that accounts for the fact that not all mutations are either so deleterious such that they can be ignored, or else neutral. Retaining only the name, a familiar example, or a downstream effect is insufficient. The specialist roles and tests remain anchored in natural_sciences_engineering_health, which is why this identity is domain-specific rather than prime.

Structural Signature¶

Sig role-phrases:

Defining carrier — Alternatively, the later “fixed model” fixes the distribution of mutations’ effect on protein function, but allows the mean fitness of population to evolve.
Constitutive relation — This allows the distribution of s to change with the mean fitness of population.
Operating condition — In large N_e populations, advantageous mutations are quickly picked up by selection, increasing the mean fitness of the population.
Recognition evidence — However, if robustness to the consequences of each possible error in processes such as transcription and translation substantially reduces the cost of making such errors, larger populations might evolve lower rates of global proofreading, and hence have higher rates of error.
Admissible variation — This is supported by the fact that transcriptional error rates in E. coli depend on protein abundance (which is responsible for modulating the locus-specific strength of selection), but do so only for high-error-rate C to U deamination errors in S. cerevisiae.
Characteristic consequence — These mutations can fix in small- N_e populations through genetic drift.
Failure boundary — In large- N_e populations, these mutations are purged by selection.

What It Is Not¶

Not the whole field of natural_sciences_engineering_health. The node requires the specific identity stated by The nearly neutral theory of molecular evolution is a modification of the neutral theory of molecular evolution that accounts for the fact that not all mutations are either so deleterious such that they can be ignored, or else neutral.
Not an over-broad reading. However, because noncoding DNA substitutions tend to be more neutral, independent of population size, their rate of evolution is correctly predicted to depend on population size / generation time, unlike the rate of non-synonymous changes.
Not an over-broad reading. However, molecular evolutionists found that rates of protein evolution were fairly independent of generation time.
Not an over-broad reading. According to Ohta, however, the nearly neutral theory largely fell out of favor in the late 1980s, because the mathematically simpler neutral theory for the widespread molecular systematics research that flourished after the advent of rapid DNA sequencing.
Not automatically Premature convergence. Retrieval proximity does not establish equivalence; the two identities must be compared by carrier, operation, and failure boundary.

Scope of Application¶

Nearly neutral theory of molecular evolution applies literally inside natural_sciences_engineering_health wherever the source-defined carrier and relation can be established. Its documented habitats include:

Theory. Alternatively, the later “fixed model” fixes the distribution of mutations’ effect on protein function, but allows the mean fitness of population to evolve.
Origins. Between then and the early 1990s, many studies of molecular evolution used a "shift model" in which the negative effect on the fitness of a population due to deleterious mutations shifts back to an original value when a mutation reaches fixation.
Theory. Early work used a “shift model” in which s can vary between generations but the mean fitness of the population is reset to zero after fixation.
Theory. This assumption can lead to indefinite improvement or deterioration of protein function.
Theory. This allows the distribution of s to change with the mean fitness of population.
Documented setting. The population-size-dependent threshold for purging mutations has been called the "drift barrier" by Michael Lynch, and used to explain differences in genomic architecture among species.

Outside natural_sciences_engineering_health, the name should be retained only when these same operational conditions survive; otherwise the comparison belongs to the broader parent Theory or should be marked as analogy.

Clarity¶

A clear use of Nearly neutral theory of molecular evolution names the carrier, the operative relation, and the conditions under which the source treats the identity as present. The minimal definition is The nearly neutral theory of molecular evolution is a modification of the neutral theory of molecular evolution that accounts for the fact that not all mutations are either so deleterious such that they can be ignored, or else neutral. The strongest recognition evidence in the frozen account is: However, if robustness to the consequences of each possible error in processes such as transcription and translation substantially reduces the cost of making such errors, larger populations might evolve lower rates of global proofreading, and hence have higher rates of error. A report should distinguish that evidence from a proxy, consequence, or common implementation. It should also state the qualification However, because noncoding DNA substitutions tend to be more neutral, independent of population size, their rate of evolution is correctly predicted to depend on population size / generation time, unlike the rate of non-synonymous changes. so that a reader can reproduce the classification rather than infer it from topical resemblance.

Manages Complexity¶

Nearly neutral theory of molecular evolution compresses multiple natural_sciences_engineering_health details into a stable diagnostic relation. The source shows both the central mechanism—this allows the distribution of s to change with the mean fitness of population.—and the practical consequence—these mutations can fix in small- N_e populations through genetic drift. This compression makes cases comparable while leaving parameters, conventions, exceptions, and evidential quality explicit. It is lossy by design: local history and implementation details may be omitted only when they do not alter the defining relation.

Abstract Reasoning¶

Type the carrier. Identify the natural_sciences_engineering_health entities to which the claim applies.
State the relation. Use the source-grounded identity: The nearly neutral theory of molecular evolution is a modification of the neutral theory of molecular evolution that accounts for the fact that not all mutations are either so deleterious such that they can be ignored, or else neutral.
Check operation and conditions. In large N_e populations, advantageous mutations are quickly picked up by selection, increasing the mean fitness of the population.
Demand recognition evidence. However, if robustness to the consequences of each possible error in processes such as transcription and translation substantially reduces the cost of making such errors, larger populations might evolve lower rates of global proofreading, and hence have higher rates of error.
Test variation. Change an implementation or setting while preserving this is supported by the fact that transcriptional error rates in E. coli depend on protein abundance (which is responsible for modulating the locus-specific strength of selection), but do so only for high-error-rate C to U deamination errors in S. cerevisiae.
Run the collapse test. Remove the defining operation; if the label still seems equally apt, only a topic or correlate was retained.
Reduce cautiously. When the specialist conditions cannot be carried, route the residual comparison to Theory.

Knowledge Transfer¶

Within the home domain. Knowledge about Nearly neutral theory of molecular evolution transfers literally when a new case preserves the same carrier type, relation, and recognition test. Alternatively, the later “fixed model” fixes the distribution of mutations’ effect on protein function, but allows the mean fitness of population to evolve. Between then and the early 1990s, many studies of molecular evolution used a "shift model" in which the negative effect on the fitness of a population due to deleterious mutations shifts back to an original value when a mutation reaches fixation.

Beyond the home domain. No canonical parent is asserted for Nearly neutral theory of molecular evolution. An outside case receives the specialist name only when the same typed roles and rejection conditions can be filled literally; otherwise the comparison remains an analogy pending later graph densification.

Examples¶

Canonical¶

Michael Lynch has proposed that variation in the ability to purge slightly deleterious mutations (i.e. variation in N_e ) can explain variation in genomic architecture among species, e.g. the size of the genome, or the mutation rate. This case is canonical because it supplies a concrete carrier and lets the defining relation be checked rather than merely named.

Mapped back: carrier → the entities in the documented case; operation → The nearly neutral theory of molecular evolution is a modification of the neutral theory of molecular evolution that accounts for the fact that not all mutations are either so deleterious such that they can be ignored, or else neutral; recognition evidence → However, if robustness to the consequences of each possible error in processes such as transcription and translation substantially reduces the cost of making such errors, larger populations might evolve lower rates of global proofreading, and hence have higher rates of error

Applied / In Practice¶

However, if robustness to the consequences of each possible error in processes such as transcription and translation substantially reduces the cost of making such errors, larger populations might evolve lower rates of global proofreading, and hence have higher rates of error. The applied case shows how the identity is used under a second setting or qualification while keeping the same operative relation.

Mapped back: changed setting → Theory; invariant → The nearly neutral theory of molecular evolution is a modification of the neutral theory of molecular evolution that accounts for the fact that not all mutations are either so deleterious such that they can be ignored, or else neutral; boundary → the case exits the class when however, because noncoding DNA substitutions tend to be more neutral, independent of population size, their rate of evolution is correctly predicted to depend on population size / generation time, unlike the rate of non-synonymous changes

Structural Tensions¶

T1 — Stable identity versus admissible variation. However, because noncoding DNA substitutions tend to be more neutral, independent of population size, their rate of evolution is correctly predicted to depend on population size / generation time, unlike the rate of non-synonymous changes. The tension matters because emphasizing only one side either dissolves the identity or overstates what the evidence and domain conventions warrant.

Diagnostic: Which changes preserve the defining relation, and which replace it?

T2 — Recognition versus proxy. However, molecular evolutionists found that rates of protein evolution were fairly independent of generation time. The tension matters because emphasizing only one side either dissolves the identity or overstates what the evidence and domain conventions warrant.

Diagnostic: Does the cited evidence establish the identity or only a correlated sign?

T3 — Definition versus implementation. According to Ohta, however, the nearly neutral theory largely fell out of favor in the late 1980s, because the mathematically simpler neutral theory for the widespread molecular systematics research that flourished after the advent of rapid DNA sequencing. The tension matters because emphasizing only one side either dissolves the identity or overstates what the evidence and domain conventions warrant.

Diagnostic: Is the observed implementation constitutive, optional, or merely common?

T4 — Scope versus overextension. The “fixed model” provides a slightly different explanation for the rate of protein evolution. The tension matters because emphasizing only one side either dissolves the identity or overstates what the evidence and domain conventions warrant.

Diagnostic: Can every claimed application fill the same typed roles without metaphor?

T5 — Transfer versus domain accent. Alternatively, the later “fixed model” fixes the distribution of mutations’ effect on protein function, but allows the mean fitness of population to evolve. The tension matters because emphasizing only one side either dissolves the identity or overstates what the evidence and domain conventions warrant.

Diagnostic: Does the receiving case instantiate Nearly neutral theory of molecular evolution literally, co-instantiate Theory, or only resemble it?

T6 — Autonomy versus reduction. This allows the distribution of s to change with the mean fitness of population. The tension matters because emphasizing only one side either dissolves the identity or overstates what the evidence and domain conventions warrant.

Diagnostic: What does Nearly neutral theory of molecular evolution distinguish that the broader parent Theory leaves together?

Structural–Framed Character¶

Nearly neutral theory of molecular evolution is structural-leaning. Its structural side is the repeatable organization summarized by The nearly neutral theory of molecular evolution is a modification of the neutral theory of molecular evolution that accounts for the fact that not all mutations are either so deleterious such that they can be ignored, or else neutral. Its framed side is the natural_sciences_engineering_health vocabulary that fixes the carrier, evidence, exceptions, and admissible transformations.

Evaluative weight: the identity can be stated descriptively even when applications carry practical stakes. Human-practice dependence: the source-grounded carrier determines whether the relation exists independently or is constituted by a practice. Institutional origin: disciplinary conventions stabilize the name and test. Vocabulary portability: In large N_e populations, advantageous mutations are quickly picked up by selection, increasing the mean fitness of the population. Import versus recognition: literal transfer requires the same mechanism; shape alone is analogy.

Its portable skeleton is Theory. Its character: a recurring specialist identity whose thin organization can be abstracted, while its operational meaning remains domain-bound.

Structural Core vs. Domain Accent¶

What is skeletal. The nearly neutral theory of molecular evolution is a modification of the neutral theory of molecular evolution that accounts for the fact that not all mutations are either so deleterious such that they can be ignored, or else neutral. The stable skeleton is the typed relation expressed in that definition and the entry's recognition and collapse tests. The source identifies these operative conditions: Alternatively, the later “fixed model” fixes the distribution of mutations’ effect on protein function, but allows the mean fitness of population to evolve. This allows the distribution of s to change with the mean fitness of population. It further constrains recognition and variation through: In large Ne populations, advantageous mutations are quickly picked up by selection, increasing the mean fitness of the population. However, if robustness to the consequences of each possible error in processes such as transcription and translation substantially reduces the cost of making such errors, larger populations might evolve lower rates of global proofreading, and hence have higher rates of error.

What is domain-bound. natural sciences engineering health supplies the operative entities, technical vocabulary, warrants, and exceptions that make Nearly neutral theory of molecular evolution literal. Its documented scope includes the condition that Alternatively, the later “fixed model” fixes the distribution of mutations’ effect on protein function, but allows the mean fitness of population to evolve. Another bounded application condition is that Between then and the early 1990s, many studies of molecular evolution used a "shift model" in which the negative effect on the fitness of a population due to deleterious mutations shifts back to an original value when a mutation reaches fixation. These are not decorative examples; they determine which carrier and evidence can fill the abstraction's roles.

Why no parent is asserted. Removing those specialist details does not currently yield one live catalog node that is a necessary genus for every instance. The entry is therefore approved as unparented rather than attached by topical resemblance. Its collapse evidence remains specific—This is supported by the fact that transcriptional error rates in E. coli depend on protein abundance (which is responsible for modulating the locus-specific strength of selection), but do so only for high-error-rate C to U deamination errors in S. cerevisiae.—and future graph densification may discover a defensible relation only if it preserves that boundary.

This entry is a kind of Theory.

Approved unparented node. No current live node supplies a defensible necessary genus or structural prerequisite for Nearly neutral theory of molecular evolution. The reviewed identity is: The nearly neutral theory of molecular evolution is a modification of the neutral theory of molecular evolution that accounts for the fact that not all mutations are either so deleterious such that they can be ignored, or else neutral. The accelerated suggestion was declined because topical or lexical similarity does not establish hierarchy; the node is admitted without a parent pending later graph densification.
Related reasoning operations. Evidence, representation, comparison, classification, transformation, or evaluation may participate in particular cases, but participation does not make any one of them a necessary parent of every instance.

Relationships to Other Abstractions¶

Current abstraction Nearly neutral theory of molecular evolution Domain-specific

Parents (1) — more general patterns this builds on

Nearly neutral theory of molecular evolution is a kind of Theory Prime

Nearly neutral theory of molecular evolution is a strict kind of Theory: its frozen identity entails the parent's defining structure while adding domain-specific restrictions.

Hierarchy paths (2) — routes to 2 parentless roots

Nearly neutral theory of molecular evolution → Theory → Formalization → Representation → Abstraction

Show alternative path (1)

Neighborhood in Abstraction Space¶

Nearly neutral theory of molecular evolution sits in a moderately populated region (53^rd percentile for distinctiveness): it has near-neighbors but no dense thicket of look-alikes.

Family — Selection, Speciation & Experimental Evolution (22 abstractions)

Nearest neighbors

Error catastrophe — 0.87
Differential Evolution — 0.85
Bacteriophage Experimental Evolution — 0.85
Complete mixing — 0.85
Vicar of Bray (scientific hypothesis) — 0.85

Computed from structural-signature embeddings · 2026-10-08

Not to Be Confused With¶

Theory. The parent omits the specialist differentia. Tell: Can the case establish The nearly neutral theory of molecular evolution is a modification of the neutral theory of molecular evolution that accounts for the fact that not all mutations are either so deleterious such that they can be ignored, or else neutral?
Premature convergence. The failure mode in an evolutionary algorithm where population diversity collapses around a suboptimal region before adequate exploration occurs. Tell: Which entry's carrier, operation, and failure condition are satisfied?
Evolutionary rescue. Population persistence under environmental deterioration because natural selection raises the frequency of heritable variants fast enough to reverse decline. Tell: Which entry's carrier, operation, and failure condition are satisfied?
Hardy-Weinberg Principle. Fix the exactly computable genotype baseline (p², 2pq, q²) a diploid population would reach under no evolutionary forces, so that any observed deviation becomes diagnostic evidence of which force — selection, drift, inbreeding, or technical error — is acting. Tell: Which entry's carrier, operation, and failure condition are satisfied?
A measurement, proxy, or consequence. Those may provide evidence without being the identity. Tell: Would Nearly neutral theory of molecular evolution remain present if the detector or downstream effect changed?
A metaphorical analogue. A similar shape outside natural_sciences_engineering_health lacks the specialist mechanism. Tell: Do the native roles transfer literally, or only the parent Theory?

References¶

Frozen Wikipedia discovery revision: https://en.wikipedia.org/wiki/Nearly_neutral_theory_of_molecular_evolution (revision 1249512386).
Preserved source candidate: http://authors.library.caltech.edu/5456/1/hrst.mit.edu/hrs/evolution/public/nearlyneutral.html

The frozen Wikipedia revision is discovery provenance. The retained source set was reviewed for identity, formal or operational relation, and scope. The encyclopedia's structural synthesis is bounded to those claims; a thin authority surface is recorded as a nonblocking source-strengthening repair rather than concealed.