Cultural norms of exogamy and mobility shape genetic evolution of Central African hunter-gatherers.

Genetic diversity in two Central African hunter-gatherer populations is maintained through interacting effects of population size, mobility, and marriage norms, keeping homozygosity similarly low.

• Why it matters: The mechanisms by which hunter-gatherer societies preserve genetic diversity after ecological and demographic shocks are not well understood.
• What they did: Using integrated genomic, demographic, mobility, and ethnographic data, the study tests selection against background homozygosity and links runs of homozygosity to reproductive success, while comparing two populations’ mobility and exogamy rules.
• The result: Modest increases in runs of homozygosity, even with near absence of close-kin marriages, are associated with reduced reproductive success; distinct strategies—strict exogamy with high mobility versus relaxed exogamy with longer male mate-search distances—produce similarly low homozygosity.