Ultimately, it’s an ideal that leads to its own undoing, because what’s natural is human variation. For a lot of people, and probably disproportionately for women, sexual exclusivity is a preference and even something that they truly want to practice — but to the extent that it becomes a universal ideal, then any breach of it becomes a source of public humiliation as well.

You say that women disproportionately value the monogamous ideal. Is this another one of nature’s cruel jokes?

You could say that heterosexuality is nature’s cruel joke [laughs]. I don’t want to exaggerate the differences [between the sexes], because one of the things that’s very clear is that men and women of the same social world are more like each other than women are like all women or men are like all men. So it’s a mistake always to exaggerate the differences between men and women — we’re always talking about average differences and a broad curve.

Reproduction is probably a piece of why a higher percentage of women than men prefer sexual exclusivity, or practice it. You can’t sort out which part is cultural socialization and which part is some kind of bio-evolutionary residue, but it’s very clear that women can only reproduce during a certain period of their life and men can reproduce a lot longer. Also, men don’t know who their actual biological children are, which has a lot to do with marriage and family systems.

What’s driving our interest in monogamy?

Historically, the male interest wasn’t necessarily in monogamy but rather in women’s sexual behavior. Even under polygamist systems, women weren’t allowed to have sex with other people. For most male dominant societies, you have a strong emphasis on wanting to know who are the proper heirs and to have control over the offspring in order to have access to the labor force — at least when children provided farm labor. So there were lots of incentives, and men had the power in both societies, both cultures to force a great deal of sexual restriction on women without necessarily living up to it themselves.

I’ll tell you about a very different society that I write about in my book, and that’s the Mosuo people of southwestern China, an ethnic minority culture that does not insist on or value monogamy, nor does it care about biological paternity. It’s a maternal extended family system in which adult children stay in the mother’s extended family compound. They have “night visiting,” there’s no double standard of sexuality, men and women are each free to have as many or as few lovers as they wish. They can have exclusive long-term lovers, they can have multiple partners, they can be chaste, whatever. And all of the children that are born to the women belong to that family’s household; the biological mothers and fathers don’t live together. They don’t have marriage, and the children are brought up by basically aunts, uncles and grandmothers.

In some ways that sounds like a utopia. What are the downsides to that sort of system?

Yeah, it does sound like a utopia to a lot of people. But it’s not really a feasible system if you’ve got economic and geographic mobility. It depends on a collective family property system without a lot of change. As for downsides, they teach against sexual jealousy, but it doesn’t mean sexual jealousy doesn’t exist, and there are people for whom it doesn’t fit well. I think any family system is better for some people than others. But this is one system that I personally think is better for a larger percentage of the people than a lot of others are.

That’s interesting, the idea of culturally teaching against sexual jealousy. Do you think that sexual jealousy is encouraged in American culture?

Oh definitely, and in most cultures. Jealousy happens even in the Mosuo culture, but it’s much less evident and much less something that the culture endorses. You’re not supposed to be possessive of property or people.

I do think we can learn a lot from that culture. One of the things that’s interesting is that because you don’t have marriage, you don’t have divorce or singlehood or widowhood or orphans. Everyone has a family and family security. In a culture that is so divorce-prone, I think there is a lot to learn from being able to imagine different ways of providing childcare and stability.

It seems harder to challenge our notion of romantic love than monogamy.

Absolutely. As I’ve written in the book, it’s curious that the notion of fidelity should come to mean sexual exclusivity when it’s really about faithfulness. I think it should mean integrity. For many, many people, including many of the gay men I studied, monogamy is absolutely essential and they wouldn’t have it any other way. But plenty of others, including my gay male friends who have had 30-year, 40-year relationships, feel that sex can involve very little emotion and that it’s OK to have a few escapades on the side without threatening their relationships. That idea is threatening to a lot of people. I’ve had some disagreements with a number of feminists who are afraid I’m giving men permission …

I would imagine these ideas could make you enemies in nearly every political denomination.

I think I’ve done that with some of the things I’ve said recently, event though I’m not trying to impose any standard on anyone. I’m trying to get rid of “one-size fits all,” because it doesn’t. I am in no ways opposed to monogamy, far from it, but I am really opposed to imagining that it’s the only way to live and that it’s the only way a relationship can have integrity and commitment.

How likely is it that in any major way we’ll explore alternatives to monogamy in America?

On the one hand, you don’t see a lot of evidence of that, in part because of the family wars and the political capital that can be gained from mobilizing around these kinds of anxieties and issues. But I do think it’s happening clearly in some subcultures. It’s likely that gay men are going to have very stable marriages in comparison to heterosexuals, and even lesbians, but it’s not gonna be based necessarily on monogamy. I think there’s a lot more tolerance [among gay males] for that variation.

I think a lot of people worry that non-monogamy means that you are more unstable in your relationship and that monogamy is a way of guarding against outside threats to your relationship. But you’re suggesting that non-monogamy can actually help strengthen a relationship.

For some relationships. It would really threaten others. I’m not recommending it as a program, I’m recommending it as an option. I think what people have to do is negotiate and be honest about what their needs are and mate with people who have the same desires and goals. I tell a lot of stories in the book of different gay relationships, including absolute monogamy where no breach would ever be tolerated.

The idea is to make the vows that you really want to keep, and to know that over the life course you might have to renegotiate them. The idea of cheating is when you break the promise and there’s only one promise you’re supposed to make — so we’re going to get a lot of promise breakers. But if you allow people to promise what they really mean to promise and are able to do, you’ll have fewer cheaters because you would have different definitions of what cheating means. Cheating would mean breaking the terms of whatever agreement is made.

When you were saying that you’re advocating for people to be honest about what they need, it struck me that it can be hard to even personally know what’s right for you because of the way that monogamy is put on such a cultural pedestal.

You’re absolutely right. The argument against my position, one that I take seriously, is that without a template or background rules, you leave too much to negotiation and disagreements. I take it seriously, but I still think it’s a better alternative to feel an obligation to be honest with yourself and honest with your partner.