UC Santa Barbara

Many people have strong opinions about the kind of person they want to mate with or marry, and we spend a lot of time evaluating potential partners for the qualities they have. These time-consuming tasks likely have an evolutionary function—they steer us toward mates that have qualities that will increase our reproductive success. While this assumption has been experimentally tested in animals, the same experimental methods are not possible in humans. Instead, we have to rely on existing cultural systems where there is variation in the amount of independent mate choice individuals get to exercise. One such case is arranged marriages, an ethnographically common system in which parents are deeply involved in choosing a partner for their offspring, sometimes with little input from the marrying individuals. Evidence indicates that parents arranging a marriage are not evaluating sons- or daughters-in-law based on the same qualities that offspring would use to find a match on their own. Therefore, individuals in arranged marriages, who are not expressing their evolved mate preferences, should have reduced reproductive success. This dissertation tests this prediction using data from the Chitwan Valley Family Study (Axinn et al., 2023). These analyses show that there are no differences in total births, offspring survival, or interbirth intervals between individuals in arranged and non-arranged marriages, which is not in line with predictions. To investigate why arranged and non-arranged marriages have similar reproductive outcomes, I then examine the alternative benefits provided by arranged marriages in Dhading, Nepal, demonstrating that arranged marriages offer substantial social and financial incentives. I then examine divergence between the in-law/partner preferences of parents and offspring in Dhading, identifying significant disagreement over several traits, including physical attractiveness and caste identity. Together, these results indicate that, while individuals in arranged marriages may miss out on fitness benefits gained by independent mate choice, the alternative social and financial benefits of arranged marriage may compensate for those losses. Thus, individuals in arranged and non-arranged marriages may be obtaining similar reproductive outcomes via alternative pathways. These results highlight the role of kin and social support in human mating systems, which is likely unique among animals.