Why is CCR5-Δ32 common only in Europe?
CCR5-Δ32 likely rose under strong selection and spread fast by long-range dispersal; its range is limited more by time than by southern selection barriers.
Source
The geographic spread of the CCR5 Delta32 HIV-resistance allele
What they did
Fit a spatially explicit wave-of-advance model to Δ32 frequency clines and allele-age estimates.
What they found
Strong selection (s≥0.1) and rapid long-range dispersal are needed; geographic restriction fits limited dispersal time better than purely local selection; origin may be outside northern Europe.
The limits
What it doesn't show
Does not definitively identify the historical selective agent (plague vs smallpox debated).
Key terms
- CCR5-Δ32
- 32-bp deletion conferring HIV resistance when homozygous.
- Wave of advance
- Spatial model of allele spread under selection and dispersal.
- Selection coefficient (s)
- Relative fitness advantage of an allele.
- Geographic cline
- Gradual allele-frequency change across space.
Flashcards
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Quiz yourself
Δ32 range limit mainly reflects
Common questions
What limits Δ32’s range?
Limited time to disperse more than local selection alone.
How strong was selection?
Models require s ≥ 0.1.
Where is it found?
Europe, West Asia, North Africa; north–south cline.
Selective agent settled?
No—plague proposed, smallpox also plausible.
More on Natural selection