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Haldane's Sieve

Explain why new beneficial mutations that are dominant fix far more often than recessive ones — because while rare an allele sits almost only in heterozygotes, so selection sees a dominant from its first copy but is blind to a masked recessive, which usually drifts to loss before homozygotes form.

Core Idea

Haldane's sieve (Haldane, 1927) is the population-genetic result that new beneficial mutations fix far more readily when dominant than when recessive. The mechanism is visibility: while rare, an allele exists almost only in heterozygotes, so a dominant one's advantage is expressed and selected from the first copy, while a recessive one is masked and drifts as though neutral, usually lost before homozygotes form. The population acts as a filter, and the fixed record of adaptation is a dominance-biased sample.

Scope of Application

Haldane's sieve lives within the population-genetics and adaptation subfields of biology, ranging over diploid sexually-reproducing populations under selection — its load-bearing content being irreducibly quantitative (dominance coefficient, h·s selection, ½N_e initial frequency).

  • Adaptive evolution theory — fixed alleles skew toward dominants relative to mutational input.
  • Crop genetics — dominant resistance genes spread faster via single-cross introgression.
  • Antibiotic and pesticide resistance — spreading alleles are dominance-biased on the target trait.
  • Conservation genetics — small populations retain fresh recessive variation poorly.
  • Hard-versus-soft-sweep theory — the reason the two sweep classes differ in dominance.

Clarity

The sieve dissolves a puzzle: the dominance composition of alleles that actually fix looks unlike the mutational input — too many dominants. It needs no special mechanism, only the fact that a rare allele sits almost only in heterozygotes. The clarifying move separates the mutational input from the fixed record and names the population as the filter between them, so a sweep's genomic signature is understood as a dominance-biased sample, not a random draw. It also makes crisp the new-mutation-versus-standing-variation boundary.

Manages Complexity

The fate of a new allele depends on a tangle of interacting quantities — dominance, selection coefficient, effective population size, mutation rate, initial frequency — through stochastic dynamics no one wants to integrate by hand. The sieve compresses that joint dependency into one qualitative principle and turns the rest into readable regime switches: one boundary condition (new mutation versus standing variation) decides whether the sieve bites, and population size fixes its strength. The analyst reads the outcome off that compact set.

Abstract Reasoning

The sieve runs on three parameters — dominance, the new-mutation-versus-standing-variation boundary, and population size. A diagnostic move infers a hidden property of the mutational process from the swept record (a dominance-biased sample); an interventionist move raises a recessive's frequency past the homozygote-forming range to bypass the filter; a boundary-drawing move places a case as hard sweep or soft sweep before predicting; and a predictive move forecasts the dominance difference between the two sweep classes.

Knowledge Transfer

Within population genetics the sieve transfers as mechanism across all diploid sexually-reproducing organisms, because the cargo is one quantitative result — effective selection on a rare allele scales with h·s, and recessives drift to loss before homozygotes form. It carries directly into crop genetics, antibiotic and pesticide resistance, conservation genetics, and the hard-versus-soft-sweep literature, plus adjacent masked-at-low-frequency settings. Beyond diploid selection the quantitative machinery does not travel; only the bare visibility intuition does, and the genuinely portable content is the more general selection-visibility pattern — a selector samples only what is expressed — a candidate parent riding alongside genetic_drift.

Relationships to Other Abstractions

Local relationship map for Haldane's SieveParents appear above the current abstraction, mutual partners to the right, and children below. Node labels state whether each abstraction is prime or domain-specific; colors identify relation types.Haldane's SieveDOMAINPrime abstraction: Selection-Visibility Gate — is a kind ofSelection-Visib…PRIME

Current abstraction Haldane's Sieve Domain-specific

Parents (1) — more general patterns this builds on

  • Haldane's Sieve is a kind of Selection-Visibility Gate Prime

    Haldane's sieve is selection visibility specialized to a new beneficial allele whose heterozygous expression scales with dominance while it is rare.

Hierarchy path (1) — routes to 1 parentless root

Neighborhood in Abstraction Space

Haldane's Sieve sits in a crowded region of the domain-specific corpus (31st percentile for distinctiveness): several abstractions share nearly its structure, so a description that fits it tends to fit its neighbors too.

Family — Population Genetics & Kin Selection (10 abstractions)

Nearest neighbors

Computed from structural-signature embeddings · 2026-07-12