Steve Stewart-Williams investigates why the ‘green-eyed monster’ evolved in humans, and indeed why it might just have helped us survive.

Imagine that a close friend came to you one day, weeping inconsolably. “What’s wrong?” you ask. Your friend then drops a bombshell: “I just found out – Alex is cheating on me!”

How would you respond to this? One way you probably wouldn’t respond is to say: “And that’s upsetting… why?” Most of us “get” jealousy. Even before we experience it ourselves, we intuitively understand that most people would be deeply upset if a boyfriend, girlfriend, husband, or wife cheated on them.

To an alien scientist, however, poorly versed in the ways of human beings, jealousy would be something of a mystery. We don’t usually mind our friends having other friends. Why, then, are most of us so worried about our sexual partners having other sexual partners? We don’t usually mind our sexual partners having a nice meal without us. Why, then, are most of us so worried about our sexual partners having a nice sexual encounter without us? Things would function so much more smoothly if we didn’t worry. So, why don’t we just do that?

Bamboozled by our bizarre behaviour, the first thing the alien scientist would want to know is where this emotion called jealousy came from. Is it built into human nature, like the capacity for fear or hunger? Or is it an invention of culture, like money or a seven-day week? This is a question that many human scientists have asked themselves as well – and which we’ve recently made progress in answering.

Is jealousy a social construct?

On one side of the debate, are those who claim that jealousy is an invention of culture. Defenders of this view argue that, in many cultures, jealousy is just as much a stranger as it would be to our alien scientist. Among the Inuit, for instance, tribal chiefs sometimes offer their male guests one of their wives for the night. This shows, so the argument goes, that sexual exclusivity is a Western fetish and jealousy a Western neurosis.

Indeed, even in the West, some people refuse to tow the jealousy line. To take just one example, the actress Shirley MacLaine once said “I’ve never really had sexual jealousy.” This is hard to square with the notion that jealousy is “in the genes.” Or so some argue.

But are they right? No doubt, jealousy is shaped in part by learning and culture. But did culture really create jealousy out of nothing? Could we really just as easily learn to be overjoyed about our partners cheating on us as to have our hearts torn in two? And are there really cultures where people are indifferent to their partner’s “extracurricular” sexual activities?

According to evolutionary psychologists, the answer to all these questions is no. Jealousy is part of our nature, found in people all over the world. Claims to the contrary, argue the evolutionary psychologists, tend to crumble on closer inspection.

Take Inuit wife-sharing. At first glance, this does look like a counterexample to the idea that sexual possessiveness is a human universal – but only if we assume that sharing one’s wife is no big deal to the Inuit. That’s not doing the custom justice, though; the whole point is that it’s a hugely generous gesture. And it’s generous because the Inuit, like human beings everywhere, are possessive of their spouses and lovers. How do we know? Because among the Inuit, male sexual jealousy is a common cause of spousal violence. Ditto other societies supposedly devoid of jealousy.

Certainly, there are individual exceptions. But they’re few and far between. That’s why, when Shirley MacLaine announces that she’s never really experienced jealousy, it makes headlines around the world. Most people have experienced it. Like it or not, jealousy is a constant companion of love: an uninvited guest we can never quite banish, try though some of us might.

Born this way

But if that’s true, why? Why would natural selection burden us with such a disruptive emotion? The answer from evolutionary psychology is that jealousy evolved to motivate “mate guarding,” and that mate guarding is a solution to an ancient adaptive problem: infidelity.

Infidelity is not particularly common in our species – but it’s not particularly rare either. And what’s true of humans is true as well of many other animals. In the 1986 film Heartburn, Meryl Streep’s character complains to her father that her new husband is having an affair. The father responds, rather heartlessly, “You want monogamy? Marry a swan.” But around the same time, scientists discovered that swans – and indeed most pair-bonding species – are just as prone as humans to the occasional “extramarital” dalliance. And for humans and nonhumans alike, such dalliances are a serious threat to the partner’s evolutionary success.



nate henry

nate henry

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nate henry
nate henry

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