Why Do Humans Have Sex in Private? Evolutionary Psychology has a Guess

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Here’s a fun thing to think about in the name of science: why do humans have sex the way they do? You know, with the whipped cream and the inflatable penguin and the laser pointers? (That’s how everyone has sex, right?)

Props aside, it does seem that most people prefer to have sex with one another in private, away from other humans. Sure, you have your occasional exhibitionist but it seems as though they are getting off on the idea of getting off with other people around because it’s taboo. So anthropologist Yitzchak Ben-Mocha from Zürich University decided to try to figure out why, and in his conclusion, the reason why we fuck in private is because men don’t want their bros to get see them and then get all horny and maybe try to get it on with their ladies. This also prevents said bros from getting jealous, which would mean that the next time they’re all at the bar they might not wingman for him. Because he fucked that chick right in front of them. UNCOOL, KYLE.

While this would be a fascinating scientific result, unfortunately, Ben-Mocha did not do any actual research that might tell us why that’s true. Because this is just another example of evolutionary psychology, the “scientific” version of Who’s Line is it Anyway because everything’s made up and the points don’t matter.

In the study, published this month in Proceedings of the Royal Society, Ben-Mocha looked through thousands of cultural studies to establish that yes, privacy during sex is nearly “universal” amongst humans, even in cultures in which privacy is hard to find. In fact, in places where (for instance) parents are forced to share bedrooms with their children, they encourage children to hide, or they have sex outside — at least, according to early 20th century anthropologist Bronislaw Malinowski in his unfortunately named book “Sex and Repression in Savage Society.”

Is all this true? It’s hard to say. Ben-Mocha’s data points are based on surveys, and he admits that people are often reticent to share their real opinions on taboo subjects, like whether or not they like to fuck in front of an audience. We can definitely say that the human behavior of hiding sexual activity from others is widespread and if not universal across the planet, definitely pretty close. It’s hard to say that anything is ever universal among any population of animals, because all of us are always changing and adapting to our environments. 

We definitely can’t say that it’s universal across time — behaviorally and cognitively modern humans have been around for about 50,000 years, and unfortunately we don’t have many extant sex tapes from the earliest part of that period. In fact, I don’t think we have any but feel free to correct me in the comments. Just kidding. I don’t read comments.

But let’s say sure, humans today universally prefer to bone in private. Does that mean there is a genetic component to it? No! There are lots of behaviors that are “universal,” like making music. Is there a gene that we evolved specifically to make music? We don’t know, but obviously people are furiously trying to find out, because for the past few decades it’s been hot shit to try to find the genetic component for pretty much everything, and any behavior that is considered “universal” is like a T-bone steak to evolutionary psychologists. Some of that research is good, but a lot of it misses out on the important way that our genes interact with our environment in a complex, neverending cycle.

And sure enough, like most evo psych, this paper does nothing to establish any kind of evidence for a genetic component behind our choice of where we make the beast with two backs. The best he can do is compare this human behavior with one other animal species that we know likes to do it in private: the Arabian babbler, a bird that Ben-Mocha has also studied expressly for this purpose. Let’s talk about that study, because it’s critical to his conclusion in this study.

Ben-Mocha observed 56 occasions in which Arabian babblers attempted to fuck each other, and in each of those instances they found the mating pair moved away from the group to do it in private. They came up with a few potential hypotheses for why they might do that, and then crossed each one off as necessary: 

  1. Are they avoiding predators? Only just over half of the attempts to bang occurred in easily accessible shelters that would protect them from predators.
  2. Are the males fucking in private as a signal of dominance, i.e., she’s mine and you can’t have her? They found that the males hid their requests to the females that they wanted to fuck — if they wanted to dominate their subs (ooh, sexy) they would want them to know they’re fucking, right? Uh, sure. Sure. Cross that one off.
  3. Do male birds get angry when seeing another male bird fucking and that’s why it’s hidden? Yes: once. Literally in one instance, a higher-hierarchy male bird caught a  lower-hierarchy male bird trying to get his little bird dick wet and he attacked him and chased him away. In every other instance, whenever a bird was caught trying to have sex the mating pair just split up.

So Ben-Mocha decided this means that the subordinates are hiding sex so they don’t get beat up by the alphas, but then why do the alphas hide sex? Their observations didn’t provide any positive evidence to suggest it — they were only able to cross off some of their hypotheses. So they did  what researchers have been doing for thousands of years: they made one up that they did not test and said “well if it’s none of those other things I guess maybe it’s that?” 

The made-up hypothesis is that Arabian babblers are “cooperative breeders,” which means that they all pitch in to take care of the flock as a whole even if they’re not breeding, so the dominant males hide the sex so that the subordinantes don’t get jealous and then refuse to take care of the offspring, scare away predators, and other basic community upkeep.

It’s compelling, but the problem is that they literally have no evidence for this. The bigger problem is that Ben-Mocha then charged ahead with his ultimate goal, which was to compare Arabian babblers to humans in this new paper, pointing out that since Arabian babblers and humans both have sex in private, maybe they do it for the same reason, and the reason he previously established in that paper (with zero evidence to support it) was that alphas want to keep the cooperation of betas.

Even if he had evidence for that hypothesis in Arabian babblers, you can’t just point to two INSANELY DISTANTLY RELATED ANIMALS and say the trait they share must have evolved for the same reason. Like, you can’t even say that about physical traits we can easily observe, let alone behavioral traits that you have no evidence are even based in genetics. About 600 million years have passed since the common ancestor that unites humans and birds. Bats are closer to birds than humans, yet their common ancestor didn’t even have wings. Wings are an example of convergent evolution, meaning a trait that they share but that evolved for different reasons at different times after those species already split. If we can’t even shrug and say that bats and birds both have wings for the same reason, where on earth does this guy get off saying that humans and Arabian babblers both fuck in private for the same reason? It’s completely unscientific and I honestly cannot believe a journal published it. 

Amusingly when Ben-Mocha’s first study came out, it got a glowing overview in National Geographic, but even that article featured a colleague at Cornell pointing out that acorn woodpeckers also conceal sex and his hypothesis is that they do it so that females can hide the paternity of the egg. Weird, a hypothesis that’s driven by what the female wants. How did that make it to print?? Ben-Mocha says that’s not likely though because “females will mate with subordinate males only after the egg laying is done, so the betas shouldn’t be under any illusion about being the fathers.” That, of course, assumes that once one egg is laid no more eggs will ever be laid, and also it suggests that if the betas are that smart then Ben-Mocha’s hypothesis wouldn’t mean anything anyway. Why would the beta males get jealous that the alpha gets to have sex, when they know they will get sex after the egg-laying is done?

Anyway, it’s all absurd. Despite the fact that this study was published in a reputable journal, there is zero evidence that you inherited a preference for fucking in private from your parents, that you fuck in private because men want other men to still be their bros, or that’s even what is happening in bird populations the study is based on. You may as well say that humans evolved a gene that allows us to hold in a fart around someone we find attractive. Not everything is an adaptive trait.

Rebecca Watson

Rebecca is a writer, speaker, YouTube personality, and unrepentant science nerd. In addition to founding and continuing to run Skepchick, she hosts Quiz-o-Tron, a monthly science-themed quiz show and podcast that pits comedians against nerds. There is an asteroid named in her honor.

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