Genetic markers of cousin marriage and honour cultures

Honour cultures, characterized by violent responses to perceived threats to personal or family honour, are widespread. Honour killings, one of the manifestations of honour cultures, claims the lives of thousands of women each year, often at the hands of close relatives, representing not only a social problem but also an evolutionary puzzle. They typically follow accusations of sexual impropriety and are the most extreme manifestation of a range of punishments that control the sexual and marital choices of women. The origins of such practises remain unclear, though honour cultures frequently occur where cousin marriage is common. We propose that cousin marriage offers kin benefits through wealth consolidation yet may also generate parent-offspring conflict over marriage choices. In response, norms and punitive measures, including aspects of honour codes, may have evolved to enforce cousin marriage. To test this, we use the average genomic inbreeding coefficient of an ethnic group, as a measure of the historical practice of cousin marriage, to show that this is associated with the likelihood of endorsing honour killings across 52 ethnic groups. We interpret our findings within the context of parent-offspring conflict over consanguineous marriage and we contribute to the growing body of research exploring the relationship between intensive kinship and cultural traits.