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Kin selection

A costly gene can still spread when it makes its carrier help relatives who likely share that gene, as long as the relatedness-weighted benefit to them (rB) outweighs the cost to the actor (C).

Core Idea

Kin selection is the evolutionary mechanism by which a costly allele can spread because it makes its carrier raise the reproductive success of relatives who carry copies of the same allele by descent. Hamilton's rule states the condition: the allele is favoured when rB > C, where r is relatedness, B the benefit to the recipient, and C the cost to the actor. Selection acts on the allele's total representation, not on any one carrier.

Scope of Application

Kin selection lives across the social-evolution subfields of evolutionary biology, wherever a heritable trait alters the reproductive success of genealogical relatives.

  • Social-insect biology — worker sterility in haplodiploid bees, wasps, and ants, where sisters share three-quarters of alleles.
  • Behavioural ecology of vertebrates — alarm calling, allomothering, and helpers-at-the-nest read as inclusive-fitness payoffs.
  • Sociomicrobiology — costly public goods maintained in clonal populations where r approaches one.
  • Plant ecology — restraint of root competition among recognised sibling neighbours.
  • Theoretical evolution — Hamilton's rule and its Price-equation generalisations as formal objects.

Clarity

Naming kin selection dissolves the paradox that self-sacrifice — sterile workers, exposed alarm-callers — should be culled by selection: the confusion came from assuming the individual is what fitness maximises. Re-anchoring the accounting on the allele turns altruism from a counterexample into a prediction, and converts the vague "is this altruistic?" into three measurable questions about r, B, and C.

Manages Complexity

The cases kin selection covers — haplodiploid workers, ground-squirrel alarm calls, microbial public goods, sibling plants — are each genetically and ecologically idiosyncratic. Hamilton's rule compresses that sprawl to one inequality over three scalars, so instead of re-deriving each case the biologist reads the outcome off the sign of rB − C, swapping only the relatedness coefficient between genetic systems.

Abstract Reasoning

The rule runs as an inference engine over just r, B, and C: an interventionist move turns one term to predict whether a trait spreads, a diagnostic move runs the inequality backwards from observed helping to a hidden quantity, and a failure-attribution move channels a non-clearing inequality into a short list of suspects. A boundary-drawing move then fixes when the calculus applies and with which coefficient.

Knowledge Transfer

Within evolutionary biology kin selection transfers as mechanism, fully and without translation: one inequality reapplied across genetic systems by swapping only r, because every case literally has alleles and identity-by-descent. Beyond biology — human nepotism, cultural in-group bias — the transfer becomes analogy that drops the measurable machinery. What genuinely travels is the thinner parent prime, inclusive_fitness: favour bearers of your replicating trait in proportion to the chance they share it.

Relationships to Other Abstractions

Local relationship map for Kin selectionParents 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.Kin selectionDOMAINDomain-specific abstraction: Hamilton's Rule — is part ofHamilton's RuleDOMAINPrime abstraction: Natural Selection — is a kind ofNaturalSelectionPRIME

Current abstraction Kin selection Domain-specific

Parents (2) — more general patterns this builds on

  • Kin selection is a kind of Natural Selection Prime

    Kin selection is natural selection specialized to heritable social effects directed non-randomly toward genetic relatives.

  • Kin selection is part of Hamilton's Rule Domain-specific

    Kin selection contains Hamilton’s rule as its operational spread criterion.

Hierarchy paths (3) — routes to 2 parentless roots

Neighborhood in Abstraction Space

Kin selection sits in a crowded region of the domain-specific corpus (9th 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