Monogamy is good, actually

How marriage evolved and why it stabilizes societies

A few ICYMI updates: I enjoyed this conversation with Daniel Muñoz, brokering a peace accord between the philosophers and psychologists of Substack. Thanks to the lovely folks who pre-ordered my book; I discovered that Substack blocked some messages, so if you sent me an order receipt and didn’t hear back or get your subscription comped, please reach out again! Also, my awesome former postdoc Anthony Vaccaro had this great piece in Scientific American, about our lab’s work on the meaning of parenthood and how it relates to men’s brain connectivity.

The below figure has been making the rounds on social media, indicating that young people, especially young women, are losing interest in marriage. Depending on your vantage point, this development reflects:

1) Feminist brainwashing to trick women into prioritizing their careers and cat-lady big-city lifestyles instead of honest love, aka the opening scene of every holiday Hallmark movie in which the heroine eventually returns to her hometown and falls in love with a humble Christmas tree farmer

2) The honest truth that marriage is a bad deal and a trap for women, who will get tricked into doing emotional labor and mankeeping for toxic men

3) The honest truth that marriage is a bad deal for men, who will get tricked into paying child support when their wives leave them for a high-earner with bigger muscles

4) The falling fortunes of men and their difficulty selling themselves as good husbands after they’ve been manosphere’d into repellant lady-deterrents

5) A product of late capitalism, which turns dating into a NPC-ridden hellscape

6) The fault of the internet, climate change, housing, AI, disappearing bees, [waves hands] things be bad

7) Fake news; people still want to get married and the divorce rate is lower than ever

There’s a case for #7 (Cartoons Hate Her had a very good recent essay making this argument), but it does seems that modern marriage has a marketing problem. Is marriage really oppressive to women? Or imprisoning to men? Why do we even have monogamy? In this essay, I’ll argue that monogamy is a little like capitalism: It’s the worst system available, except for all the others. Humans are designed to be mostly monogamous, but there’s a catch: we’re also designed to be flexible, opportunistic cheaters on occasion.

Unlike many mammals, who mate with strangers in wham-bam fashion, humans have been forming stable pair-bonds for a significant chunk of our evolutionary history. You can actually tell this by looking at the size differential between modern men and modern women; although the average woman is shorter than the average man (something of which I’m all too aware, now that my 14-year-old son has surpassed me in height), men are only about 7-10% taller than women. Compare us to gorillas, whose males are 50-100% bigger. Gorillas are polygynous, and their larger size makes it easier for them to fight their way to harem dominance. Over millions of years of evolutions, human men have gotten smaller, relative to women, and have also evolved smaller teeth – good signs that we’ve settled into more stable relationship territory.

Sexual dimorphism in the gorilla, human, and lemur

However, human men aren’t exactly the same size as women, unlike exclusively monogamous animals like lemurs, gibbons, or prairie voles. In those species, it’s hard to tell males and females apart. We’re somewhere in between.

This is true of another indicator of competition for mates: testicle size. You need big balls if you want to dominate the sperm wars. You see large testicles in promiscuous mammals, like chimps, bonobos, and rats. You see tiny testicles in the aforementioned gibbons and prairie voles. Human men are, again, somewhere in between, suggesting that we’re mostly monogamous but not completely.

Another evolutionary hack that facilitates monogamy: human women conceal our ovulation. In other words, it’s not obvious when we’re fertile (unlike, say, baboons and lizards whose genitals change colors or who do special dances or otherwise make big displays of availability during their fertile windows). There’s some evidence that human women actually do show subtle ovulation cues, like changes to their faces, voices, and behaviors, but the research on this has been mixed. If women do give off signals, they are very subtle. (By the way, speaking of ovulation: Did you know that when a male cheetah makes a particular barking sound, it causes every female cheetah in his vicinity to spontaneously ovulate? Here’s how the bark sounds…disappointingly, less like Barry White and more like a whiny kitty).

Gelada baboons signal fertility with this turkey-gobbler-like swelling on their chest.

Concealed ovulation means that men rarely know exactly when they have caused a pregnancy. If you’re a tomcat who wants to make kittens, you just find the nearest feline in heat and it’s business time. But a man who wants to pass on his genes can’t just show up once. He needs repeat opportunities, requiring him to stick around to court whichever lady friend will most consistently return his advances. This allows women to bargain for more goodies (meat, jewelry, flowers) and get more protection for their babies. A recent theory suggests that the greatest benefit to concealed ovulation might actually be to reduce conflict among women, who might otherwise aggress against those who are in fertile periods.

Concealed ovulation facilitates monogamy, because it motivates males to hang around a potential partner longer. However, it can also facilitate cheating, trickery, and confusion about which babies are whose, because women can get knocked up by an extracurricular partner without their primary partner ever suspecting. A little bit of paternity confusion can actually be adaptive for moms and babies, because it might reduce the risk of infanticide from rival males and facilitate more cooperative care. (I wrote about this here). In other words, concealed ovulation helps us form more stable pair bonds, but it also allows for some strategic subterfuge.

In sum, the evolutionary record reveals that humans have some monogamous tendencies, but we’re not universally designed for strict monogamy. You could describe our natural state as more akin to “monogamy with benefits” or “serial dating.”

When it comes to relationships, humans continue to exhibit the one characteristic that makes us unique, and uniquely adaptable, compared to other mammals. We’re flexible. We have the capacity to behave monogamously, but we can mix it up depending on the rules and expectations of our society. Enter religion, moral codes, the legal system, bridal magazines, and all the other cultural technologies that push us towards particular norms.

Marriage helps societies better identify a particular baby’s father. In patrilineal societies (in which we inherit property and status from our fathers), paternity uncertainty is a big deal. Societies have developed various approaches to monitor women’s fertile windows, such as menstrual huts and “red tents” that publicly signal the timing of everyone’s cycle, but these are thankfully being phased out in the modern world. As Cat Bohannan writes in the excellent book Eve, the whole purpose of sexism is to create “a massive set of rules that exist to control reproduction” – specifically, women’s reproduction. I think it’s fair to say that stable marriage, although it has some sexist downsides of its own, is better for women’s welfare than living in a harem and being exiled to the red tent every month.

More stable pair-bonds – that is, marriages – help to make paternity more certain and motivate fathers to contribute more to their families. But to maximize everyone’s genetic interests, monogamy-with-benefits – that is, one stable mate but dalliances, or serial partnerships - might be a good compromise. Indeed, that’s pretty much what you see in many hunter-gatherer societies: stable pair-bonds, but also fairly high rates of stepfamilies and blended families, occasional multiple-wive situations, and some sneaking around. Barry Hewlett, an anthropologist who I interviewed for my Dad Brain book, estimates that around 25 to 40 percent of marriages between Aka, Hadza, or !Kung hunter-gatherers end in divorce. There are also remarriages that occur because of death (the adult mortaility rate is fairly high), so about 40% of Aka teens live with stepparents.

The rise of agriculture – which created more stable societies – and the spread of Christianity contributed to more high-fidelity monogamous marriage norms. Nowadays, the majority of societies, globally, practice mostly monogamous marriage. (That said, even among very religious societies, you still see many exceptions to the lifetime pairing norm. Kids were about as likely to be raised by stepparents and single parents hundreds of years ago, when the Church had a stronger grip on culture, as they are today – but because of spousal death, not divorce. Women probably poisoned bad husbands on occasion, too).

When it comes to the welfare of kids, and the overall functioning of societies, monogamy is a pretty good set-up. Two parent households have more resources – both in terms of money and time – and can invest more in parenting. Monogamy also reduces competition and status inequality between males, which is good for stable societies; although there are still some polygynous societies in operation, they often have more strife. It’s a recipe for discord when one high-status man gets all the women and all the other dudes stay single forever. (There are also some polyandrous societies - that is, societies in which one woman has multiple male partners - but they’re more unusual and tend to develop under specific resource conditions. That said, one society, the Aché in Paraguay, have a very interesting model of “partiple paternity” - men sharing fatherhood - that I wrote about in the dad book). There’s also a tranche of evidence that marriage is really good for men. Married men live longer and are healthier than single men, have lower rates of addiction and commit fewer crimes, and are less likely to suffer the “deaths of despair” that come with isolation.

One could argue that marriage has become a slightly less good bargain for women over the last century or so; when women were barred from higher education and the paid workforce, marrying a man was your main ticket to income, status, and property. That’s not the case any more. Since women are more likely to take care of men than vice versa, and generally do more unpaid work to keep the household afloat (there’s plenty of data on this), the lifetime health benefit of marriage is a little more mixed for women than for men. Happily married women report greater happiness and live longer than single women, but unhappily married women fare worse. So the data suggesting that young women are less interested in marriage than previous generations actually reflects that girls are accurately forecasting their futures. Still, if you have the ability to be choosy about your partner and want kids, I would still argue in favor of marriage. I am a fan, personally. I also don’t think the answer to women’s diminished interest in marriage is to lean hard into #Repealthe19th and get-women-out-of-the-workforce discourse and tell girls to skip college in order to be tradwives. Instead, let’s raise boys to be great partners and fathers, and let’s bring back bars and church socials and mixers and bowling nights and walkable third places so that young people can actually get off their screens and meet each other in real life.

We’ve seen a surge of interest in alternatives to monogamy in the last decade or so, including the rise of multiple-partner and “ethical non-monogamy” configurations. My sense is that the popular press coverage of these phenomena has outpaced their actual prevalence, although I don’t live in San Francisco, so I could definitely be wrong. Although I’m too boringly married to have any direct experience with these arrangements, my impression is that they can be a challenge to pull off. A three (or more) person relationship requires skills and resources to navigate. You could call it a luxury belief - fine if you have the means, but not scalable for everyone. This was my takeaway from Molly Roden Winter’s best-selling memoir Open, about her own open marriage. It’s clear from her account that non-monogamy, at least when done in style, requires quite a bit of money and time. She and her husband book hotel rooms and go on spontaneous getaways with their partners, not to mention the fortune they spend on babysitting. Winter endures many tearful breakups with new partners, and her own marriage suffers too. Although she casts her non-monogamy as a vehicle for liberation and self-discovery throughout the book, she could have also learned a language or mastered a musical instrument or run for office in the time she invested into extra relationships.

I was watching “Say Yes to the Dress” with my daughter a few years ago when a throuple came in to buy not one, but two bridal gowns. Is it just me or are the women both way more attractive than this dorky guy? Apparently, they ditched him a few weeks before the episode aired and just married each other.

Although it’s not my bag, I think that the interest in non-monogamy taps into something that is genuinely lacking in contemporary marriage. As extended family and neighborhood networks have gotten sparser, we’ve heaped pressure on the two-parent nuclear family to function as both an economic and parenting unit. Our semi-monogamous heritage suggests that we are really cooperative breeders, who raise kids in community. Although they swim in different ideological lanes, Lane Scott and Lisa Sibbett have both written about the community scaffolding that wraps around a good marriage. Our culture sets up married couples to fail when we expect them to fulfill the whole family’s connection and caregiving needs in the absence of support scaffolding (whether from the state, the church, or the community) and “auntie” networks. To me, the appeal of multiple-partner configurations is less about sex and more about the value of getting extra help with the household.

To sum up: our bodies suggest that we are designed to be mostly monogamous but also to show some flexibility and the ability to adapt to different cultural contexts. Societally, monogamy seems to benefit stability and the welfare of children. Ergo, marriage is good. But we should do more to help young people form stable relationships and we should definitely do more to support parents, including married parents, because raising thriving children requires all hands on deck.

Before I get into my more official music recommendation, I should get something out of the way. When writing this piece, I could not get this song out of my head, but my brain insisted on singing the tag line as “Monogamy.” There. You’re welcome. Sorry.

MUSIC RECOMMENDATION OF THE WEEK

Past recs: Broncho // Alvvays // Capitol Years // The Cairo Gang and Hard Quartet // The Beths // Ballerina Black // James Mercer // Playboy Carti & Car Seat Headrest // Weyes Blood // Matthew Sweet // Fontaines D.C. // Elvis Costello Spanish Model // Lily Allen

GEESE

The main reason I am talking about the band Geese this week is because Molly Roden Winter, whose book Open I discussed above, is the mother of the lead singer! (I discovered this while doing research for this piece, aka googling to see if she was still with her husband). Also, Geese has been getting a lot of press lately, including a very funny New York Times article about how there is also a band with the name Goose, and it’s easy to get the two bands confused. Geese has been likened to Television and The Strokes but they’re also kind of jammy. I’m not convinced I like them, but I think they’re growing on me. This song, Taxes, starts off with a boring muffled acoustic part but then gets awesome around the 1:30 mark, which is a long time to make your audience to wait for a pay-off.

This video features a baby, and the chorus, “Baby, you can change and still choose me,” which actually sounds like something you might hear from a person whose parents had a famously open marriage.