Study finds no evidence polygyny means more unmarried men
Polygyny, where men can legally have more than one wife at once, is not the social threat it is often made out to be, research shows.
Political scientists, think tanks and some news media have warned the custom locks many men out of the marriage market, fuelling violent unrest and even terrorism.
But new research co-written by academics at Brunel University of London shows the opposite is often true. In communities where polygyny is common, men are more likely to be married, not less.
The study, published in Proceedings of the National Academy of Sciences (PNAS), used 84 million census records from 30 countries in Africa, Asia and Oceania, collected between 1969 and 2016. A research team including demographer Hampton Gaddy, anthropologist Laura Fortunato and evolutionary behavioural scientist Rebecca Sear also drew on historical records from the 1880 US census, focusing on Mormon communities where polygyny is the norm.
“There’s a common assumption in evolutionary science, policy, and even pop culture, that polygyny is destabilising because it leaves too many men without partners,” said Dr Rebecca Sear from Brunel’s College of Health, Medicine and Life Sciences. “But our data shows that’s not always true. You need to look at the demography — and that often tells a very different story.”
In just six out of 74 censuses studied (8%), regions with more polygynous marriages had more unmarried men than monogamous ones. But in 34 censuses (46%), the pattern was reversed — polygyny resulted in fewer single men. The rest showed no clear link either way. In the US data, states with widespread Mormon polygyny had lower rates of unmarried men than neighbouring ones. And this finding stood after adjusting for differences in local sex ratios.
It means, the study says, that the simple logic — ‘if one man marries two wives, another man goes without’ — falls apart when you look at real-world population data. Age gaps, life expectancy differences between men and women and population growth all influence how marriage markets really work.
‘High-polygyny societies’ where polygynous marriage is widespread often value marriage more intensely, researchers suggested. In sub-Saharan Africa, where polygyny is most common, men are less likely to remain childless and people tend to choose to have bigger families. In 19th-century Mormon communities, strong religious and social pressures meant that polygynous marriage was expected. These cultural norms help explain why marriage is still widespread even when some men have multiple wives.
The findings also challenge assumptions in online subcultures, including the incel movement, which claims high-status men monopolize women.
“Polygyny is often labelled a harmful cultural practice by development agencies without evidence,” said Dr Sear. “That kind of assumption can mislead policymaking. We’re not defending polygyny in our paper but what we are saying is: check the numbers first.”
Reported by:
Hayley Jarvis,
Media Relations
press-office@brunel.ac.uk