Table 1.

Hypotheses and predictions (from research literature) for costs and benefits of cousin marriage

Hypothesis	Description	Predictions
1. Inbreeding costs	Fitness costs to accumulation of deleterious alleles	Lower fertility for cousin-married than unrelated-married individuals. Lower child survival for cousin-born than unrelated-born individuals
2. Genetic/environmental rescue	No inbreeding costs, owing to genetic rescue	Same fertility for cousin-married and unrelated-married individuals. Same survival for cousin-born and unrelated-born individuals
3. Mate scarcity	More opportunities in societies with limited partners	Lower age at first reproduction for cousin-married than for unrelated-married individuals
4. Kin benefits	Access to wealth, inheritance and alliances within families	Higher survival for cousin-born than for unrelated-born individuals. And/or, higher survival and fertility, and lower age at first reproduction for cousin-married than for unrelated-married individuals
5. Immune response benefits	Preserving co-adapted gene complexes that control immune response to pathogens	Higher survival for cousin-born than for unrelated-born individuals