Being in a marriage or long-term relationship typically includes promises of monogamy, but new research shows a surprising number of folks, mostly men, are open to the idea of having another person in the mix.

Fully one-third of men in the United Kingdom are open to the idea of having more than one wife or long-term girlfriend, while only 11% of women would want someone else in their relationship, results show.

Those trends hold when considering both types of polygamy, researchers said.

Those are polygyny, a man marrying more than one woman, or polyandry, where a woman marries more than one man, researchers found.

About 9% of men said they would share their partner, versus 5% of women interested in such a relationship, according to the report in the Archives of Sexual Behavior.

“This study shows that a sizable minority of people are open to such relationships, even in the U.K, where such marriages are prohibited,” said lead researcher Andrew Thomas, a senior lecturer in psychology at Swansea University in Wales.

“Interestingly, many more men are open to the idea than women — though there is still interest on both sides,” Thomas added.

For this study, researchers asked 393 heterosexual men and women in the U.K. how they felt about a committed partnership in which they shared their other half with someone else.

“Comparing polygyny and polyandry directly, men were three-and-a-half times more likely to say ‘yes’ to the former than the latter, while women were twice as likely to say ‘yes’ to having more than one partner, compared to the idea of sharing their partner with someone else,”

Thomas and his colleagues noted that some cultures around the world in both the past and present have practiced polygamy and polyandry.

For example, some societies in Africa and the Middle East have long-standing traditions of polygyny, while some communities in Tibet and Nepal practice polyandry, the researchers said.

“Committed non-monogamy has received a lot of attention recently,” Thomas noted in a university news release. “It’s a hot trend with more and more couples talking about opening up their relationships to include other people. However, these types of relationship are far from new.”

“While most seek monogamous relationships, a small proportion of humans have engaged in multi-partner relationships throughout human history, especially polygynous marriage where one husband is shared by several co-wives,” Thomas added.

More information

The Pew Research Center has more about polygamy.

SOURCE: Swansea University, news release, Dec. 12, 2023