New study challenges mechanism linking polygynous marriage to social ills
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A new study co-authored by Laura Fortunato, Professor of Evolutionary Anthropology at the University of Oxford, alongside colleagues from the London School of Economics and Brunel University London, challenges a long-standing claim that polygynous marriage, where men have multiple wives, creates a surplus of men with no prospect of ever marrying. A large contingent of unmarried men is widely believed to lead to negative social outcomes, including interpersonal violence and, in extreme cases, civil conflict.
The research, led by Hampton Gaddy at the London School of Economics, was published in Proceedings of the National Academy of Sciences (PNAS). Combining demographic modelling and census data from 30 countries across Africa, Asia and Oceania between 1969 and 2016, as well as census data from the 19th-century United States, the team found that polygyny often coexists with high rates of marriage among men. This pattern contradicts the idea that polygyny leaves large numbers of men without wives.
For example, across over 84 million individual records in the 30-country sample, the researchers found that the association between the prevalence of polygyny and the prevalence of unmarried men at the sub-national level is negative in nearly half of the censuses (34 out of 74 censuses), and positive in less than 10% (6 of 34). The researchers posit that, where polygyny is allowed, cultural norms promoting marriage are likely to offset demographic and other constraints which may otherwise limit men's opportunities to marry.
Reflecting on the study’s implications, Professor Fortunato said: “Our work shows that simplistic assumptions about human affairs, while intuitive, may lead to unwarranted conclusions. In addition to shaping popular discourse, these conclusions often make their way into policy interventions, with real-world repercussions for millions of people around the world. So we must look at the data carefully and exercise great caution in their interpretation.”
The authors emphasise that the research does not endorse polygyny, nor any other marital arrangement. Instead, it calls for a more nuanced, evidence-based understanding of how family systems interact with broader social and cultural dynamics.
