Inbreeding avoidance in the Raute hunter-gatherers from Nepal

Area of Science:

• Human population genetics
• Anthropology
• Evolutionary biology

Background:

• Inbreeding depression and loss of genetic diversity threaten small populations.
• Hunter-gatherer groups use mobility and exogamy to avoid inbreeding.
• The role of specific cultural systems in mitigating inbreeding risks is understudied.

Purpose of the Study:

• Investigate inbreeding patterns and avoidance strategies in the Raute of Nepal.
• Compare Raute strategies with Agta (Philippines) and Mbendjele BaYaka (Congo) hunter-gatherers.
• Analyze the impact of the Raute's patrilineal clan-based exogamic marriage system on inbreeding.

Main Methods:

• Genome-wide single nucleotide polymorphism (SNP) data analysis.
• Kinship analysis to assess genetic relatedness.
• Population simulations to model inbreeding reduction under different mating systems.

Main Results:

• All three hunter-gatherer populations exhibit elevated homozygosity and a preference for genetically dissimilar mates.
• The Raute's patrilineal clan-based exogamy significantly reduces expected offspring inbreeding compared to random mating or avoiding only close kin.
• Cultural marriage rules appear to be a compensatory strategy for demographic isolation.

Conclusions:

• Social structure significantly influences genetic outcomes in small populations.
• Cultural practices can evolve as adaptive mechanisms to mitigate the genetic risks associated with small population size.
• The Raute's marriage system demonstrates the effectiveness of cultural adaptations in maintaining genetic health.