Did Humans Evolve to Form Long-Term Relationships?

The science of long and short human relationships

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Sex is really weird.

When you think about it, for an activity that only takes a few minutes for most people, it sure does occupy a whole lot of our focus. Sex lives rent-free inside our heads on most days. 

Add in the auxiliary components of sex, like dating, forming and maintaining romantic relationships, and perhaps even marriage and children, and you realize that sex occupies a lot of our time.

“This is a man’s world,” said James Brown, “but it wouldn’t be nuthin’ without a woman,” implying that all of the monumental achievements that men have undertaken have been to attract women. This caricature of male motivations speaks to us because it highlights how much attention we give sex and relationships, even if it isn’t exactly accurate.

And yet, for all our effort in relationships, we’re spectacularly bad at them. 

Psychologist Erich Fromm writes, “There is hardly any activity, any enterprise, which is started with such tremendous hopes and expectations, which fails so regularly as love,” and he’s absolutely right.

Love fails more often than not.

We spend a ton of time thinking about sex and relationships. But rarely do we stop and ask ourselves what kind of relationships we’re best at. What kind of relationships did we evolve to have with others? 

Answering this might help us illuminate things about who and how we love as humans.

Non/Monogamy?

In our quest to understand the nature of love, a few camps have emerged. 

• There are the monogamists, those die-hard romantics who swear that humankind’s purpose is to form lifelong pair bonds and raise families, passing along their wisdom and genes to the next generation. They hold this view even in the face of rampant cheating, swinger communities, and daily instances of infidelity that shatter dreams and break marriages.

• Then there are the polyamorists, the monogamists’ arch nemeses, who profess non-monogamy as the standard mode of human life and monogamy as totally unappealing and even unnatural. Here, you find the cynics, the realists, those who’ve gone down the long, often-barren path of marriage and long-term relationships and found that something was missing.

• And then there’s a third group. This group rarely gets talked about. They’re the serial monogamists of the world. Though they might not always admit it, this group thinks that humans were designed to engage in successive short-term relationships characterized by explosive, often experimental sex, deep passion, and romance that subsides just as quickly as it sets in, at which point they jump ship and move along to catch the next love buzz.

The serial monogamists of the world split the difference between the two. Famed anthropologist and author Helen Fisher falls into this camp. Throughout the 1980s, Fisher explored the sexual structures of 58 different societies all over the planet. 

Her research, combined with research from past anthropologists, found that people usually have a baby every four years. This is called the interbirth interval. 

Fisher theorized that we may have evolved to form strong, passionate, romantic attachments with one special person for a period of about four years before the flood of chemicals that we call “love” subsides.

There’s lots of good evidence backing up this theory. For starters, all over the globe, the interbirth interval seems to be about four years old, which is incidentally about the same age that children are weaned off of milk and can eat solid foods. It’s also a moment of fruition, as most children who die in nature die before the age of four. 

Fisher hypothesized that nature shaped us to come together just long enough to create a baby and see it through until it could be reasonably expected to survive into adulthood, barring natural disasters, war, and disease.

It’s a grim perspective for the hopeful monogamist. Yet, lifelong marriages and relationships persist across the globe. Where do they come from?

Do they have the goods on how to make love last? Are they holding out on us? 

Tell me your secrets!

The Genetics of Non/Monogamy

Let me just say, I hope as you read through the previous section, you were asking yourself where you fit along this spectrum of monogamy. Some people don’t hesitate to proudly declare themselves in one camp or the other.

If you know where you stand, awesome, if not, hey, life goes on. I’m sure you’ll figure yourself out as it happens.

I mention this because there’s some interesting evidence suggesting that our predispositions to non/monogamy are genetically based. RS3 334 was the first gene discovered to play a role in our inclinations to monogamy, but since then, 24 genes have been identified with animal (non) monogamy so far, and more may someday be uncovered.