Leaving your wife and your brothers: when polyandrous marriages fall apart.

Polyandry challenges both traditional sociocultural and evolutionary understandings of marriage. Its existence calls into question the importance of female sexual exclusivity and reproduction in marriage, two fundamental aspects of the affinal bond in most other marital forms. How does polyandrous marriage persist? When does it dissolve? This paper examines marriage patterns in the fraternally polyandrous Tibetan communities of northwestern Nepal, highlighting the most important factors associated with both the maintenance and dissolution of polyandrous unions. Behavioral ecological analyses of polyandry to date have focused on univariate analyses of the economic and fertility correlates of the two primary marital forms observed in nominally polyandrous communities, polyandry and monogamy. In this analysis, multivariate regression and survival analysis are used to extend our understanding of the factors that precipitate partitioning among the polyandrous marriages in the study. Wealth, long thought to be a major force shaping marital decisions in these communities, is modeled in both quantity and quality in this study. This represents an important departure from previous studies, as analyses show that it is not only the amount of wealth that influences the stability of polyandrous marriages, but also the type of wealth and extent to which it is diversified over economic spheres. Univariate analyses show that amount of wealth and the size of the brother/co-husband set are both associated with the probability that a polyandrous marriage will partition. Though these results support earlier findings, multivariate analyses show that controlling for other factors reduces their importance.