Popular wisdom suggests that an emotionally fulfilled life is one spent with a stable, monogamous partner by your side till death does you part. It’s the one fairytale that continues to hold truth post-childhood and indeed, there are some studies suggesting a connection between marriage or monogamy and happiness.
However, the link is far from clear-cut. It’s extremely difficult to show causation, rather than correlation, in such a major life choice, and of course the quality of the relationship matters a great deal. Then there’s the tricky matter of finding people who will tell the truth about their sexual indiscretions. In any case, there is evidence that suggests non-monogamous relationships can be just as beneficial.
Although marriage has been a western institution for centuries, the monogamy aspect has always, until relatively recently, come with a sly wink, at least for men.
Our focus on monogamy is strongly shaped by the manner in which we reproduce. Monogamy is extremely rare in the animal world, but most creatures aren’t dependent on their parents for as long as humans are. There’s a clear, evolutionary advantage to creating a stable, monogamous relationship so that children can enjoy the benefits of being raised by two parents.
But human reproductive strategies are not so straightforward. Men require relatively little investment to procreate (compared to women, who are physically required to face nine months of pregnancy followed by breastfeeding), and so it makes sense as a strategy to have an official wife and children, but also mistresses on the side.
Meanwhile, women often have to make a decision between a man with strong genetic qualities, and one who will provide a stable environment. It’s rare for a man to provide both, says Daniel Kruger, a social and evolutionary psychologist at the University of Michigan’s School of Public Health. This conundrum, he says, is why finding a socially dominant man who’s buff but also a bit of a cad, and somehow managing to woo him into stability, is such a popular fantasy.
“One long term strategy is to settle down and have a long-term relationship with a guy who’s a reliable, stable provider, but then have an affair on the side with a guy who has phenotypic qualities and can provide that high-quality genetic investment,” Kruger says.
But if either men or women are caught, this could have serious consequences for their marital union, and so human relationships become a world of “strategies and counter strategies,” he says.
This fear of a partner straying is key to maintaining the ideal of monogamy. Pepper Schwartz, a psychology professor at the University of Washington, says that most people are wary of an open relationship simply because they want to guard their mates. “Humans are territorial,” she says. “That doesn’t mean they wouldn’t want to have a [non-monogamous] experience themselves, but most people aren’t reciprocal.”
Indeed, some believe that our entire marital system was created out of this jealousy. Judith Stacey, a sociology professor at New York University who has studied relationship systems around the world, says the West’s focus on marriage and monogamy is connected to a male need to ensure their paternity. “I suspect it has a lot to do with control of women’s reproduction,” she says.
David Barash, evolutionary psychology professor at University of Washington who has studied monogamy in nature, says that this is one strong hypothesis for how human monogamy developed. A second thesis is that monogamy is a democratic institution for men. “With polygyny, a small number of men get more than their fair share of the women, leaving a number of men reproductively excluded, sexually frustrated, and liable to make trouble in all sorts of ways,” he says. “The possibility therefore exists that monogamy developed as a trade-off in which powerful men essentially agreed to forego most of their sexual and reproductive advantages in return for a degree of social peace and stability. “
Despite the conflicting biological pressures, there’s a huge amount of social emphasis on monogamy. Edward Stein, a professor of law at Yale Law School and Cardozo School of Law with a focus on family law, says there’s immense legal pressure on upholding sexual fidelity. Adultery is a criminal offense in 21 US states and, while few are prosecuted, this technicality means that people could lose their jobs or be denied housing on the grounds of being a felon for cheating. And of course, adultery is grounds for divorce, and can significantly affect alimony and custody in many states.
Stein believes that rather than penalizing adultery, the state should incentivize consensual non-monogamy, where partners remain largely committed but allow one another extramarital sexual dalliances. This is partly a public health issue, as those who have secretive affairs are far less likely to practice safe sex.
But Stein also believes that consensual non-monogamy would also allow relationships to be more open and honest. While some people may decide they want to honor monogamy in their relationships, it isn’t a necessity for everyone. To Stein, what’s morally problematic, more so than infidelity, is lying to your spouse.
“In practice, most people aren’t monogamous, even most married people,” he says. “Given that’s a fact of nature, we’ve got a choice about whether we want people to be open and honest about their non-monogamy or secretive.”
Aside from the legal restrictions, there’s also significant social pressure to choose one partner and stick with him or her. But given the evolutionary incentives to have multiple partners, it’s no wonder that monogamy can be a struggle—one that’s not made any easier by the observation that “it can get a little bit boring with one person,” as Stacey puts it.
“It’s one thing to have an exclusive relationship, it’s another to also be domestic, 24/7, seeing people in all of their less-than-glamorous states, dealing with the dirty socks on the floor and irritations,” says Stacey. “Eroticism for a lot of people in the early stages of relationships is very connected to fantasy and not knowing the other so totally, and not having them know you. It’s both fantasy and projected fantasy.”
On the other hand, creating a family with someone does not necessarily correlate with sexual desire—and certainly domesticity is far from an aphrodisiac.
Many people who are attracted to someone other than their partner take it as a sign that they’re a bad person or aren’t in the right relationship. Barash disagrees. “In fact, what such attraction indicates is that you are a healthy mammal,” he says. “Congratulations!”
Of course, many people enjoy the support, confidence, and long-term care of being in a monogamous relationship. But, for those who don’t, the pressure to conform can be stifling. Stein suggests this can lead to relationships being unnecessarily cut short.
“I think it can make people feel like failures,” he says. “We have this social and legal expectation that we should be monogamous. Society suggests that if we fail, it’s a sign for us to break up.”
Monogamy is so much the norm in Western culture, it can be strange to realize that it’s not ubiquitous worldwide.
Stacey points to what she calls a “perfectly functional” community of Mosuo women in China, which has a strong matriarchal culture. Households are organized by matrilineal lineage, meaning children live with their mother and blood relatives on their mother’s side. Women are allowed to have as many partners as they like, and sexual relationships take place during “night visits.” Uncles take the role of father figures, and any known biological fathers having an avuncular relationship with their offspring.
Meanwhile, there’s a growing polyamory movement, and plenty of couples that describe themselves as “monogamish,” meaning that they’re committed to each other but embrace the occasional fling outside the partnership. Stacey says that gay men are some of the strongest proponents of this set-up, and she’s studied many such couples who have strong and stable relationships for years, without insisting on monogamy. Stacey believes this makes sense, and that, “we should redefine fidelity to mean integrity, not sexual exclusivity.”
However others, including Barash, insist that monogamy should be seen as a virtue and, even if it isn’t natural or easy, something worth striving for. Breaking completely free of monogamy would be unlikely to have societal benefit, he says, given the importance of having two committed parents when it comes to childcare.
Perhaps a suitable alternative, for those who struggle with monogamy, would be to loosen the commitment after raising a family. Kruger says that he’s heard anecdotally of couples who’ve embraced an open relationship only once their children have left home. “We might be designed to have these relationships and intense feelings that last long enough to raise our offspring,” he says, “but once that’s achieved, it seems the glue is not so sticky anymore.”