How obedience of marriage rules may counteract genetic drift
Marriage rules are a common component of many human societies. Since these rules, translated into mating patterns, would imply inbreeding, the question arises as to their long-term population genetic effects. We show by simulation that continuous unilateral or bilateral cross-cousin mating, reflecting the most common form of prescribed marriage, increases homozygosity but at the same time slows down considerably the loss of gene diversity due to genetic drift. For X-chromosomal genes, this effect is more pronounced if marriage, translated into mating, is matrilateral rather than patrilateral. Although the maintenance of gene diversity, in principle, could have conferred a selective advantage to the initiation of marriage rules, the mechanisms driving such a move are difficult to perceive. We therefore conclude that the possible preservation of gene diversity through marriage rule-induced inbreeding is a by-product, not the source, of a cultural invention that instead rested on foresight and strategic thinking.
KeywordsMarriage rule Population genetics Inbreeding Genetic drift Social evolution Gene diversity
The authors are most grateful to Jörg Schmidtke, Hannover, for the helpful discussion.
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