Sex + Dating

Men Are Biologically Designed to Impregnate Strangers


It’s safe to say that sexually active males and females alike have at least once in their lives experienced the gut-wrenching fear of knocking somebody up -- or getting knocked up -- from a one-night-stand.

And for those of you in the midst of a holier-than-thou head shake right now because you’ve never had a one-night-stand and how dare I assume such a thing, at least admit you’ve heard about this happening to a friend or seen a movie about it and mumbled to yourself: “man, that would suck.”

Well, according to a study from researchers and Dr. Laura Sirot (a professor of biology at Wooster and evolutionary biologist), that fear is actually legit. 

Before you panic, allow us to break down the aforementioned study for you in layman's terms -- and also not layman's terms, because we got Dr. Sirot herself to provide you with all the info.

We’re just like animals... sorta

Good lord, it appears Adam Levine was singing about scientific fact! OK maybe not -- but like most things we’ve learned about human evolution and biology, the original idea for Sirot's experiment was sparked from studying the reproductive behavior of animals. 

“A lot of my friends were having trouble conceiving," the doctor explained, "and they would tell me these horror stories about these slow, invasive tests they had to go through. It made me think of all the studies I knew about in other animals where males will change the parameters of their ejaculate depending on the characteristic of the female. And one of those characteristics is whether the male has mated with her before or not. 

“The things that change in the male ejaculate are the same things that they measure in fertility clinics," Sirot continued. "We know from a long history of literature that male animals will change the quality and quantity of sperm in their ejaculate, and that is often in response to a new female. We also know males will invest more courtship in novel females. This isn't across the board in all animals, but it’s been found.

“So I thought, what if this is happening in humans too?”

Men with fertility problems may not always have problems 

The study, based on 21 subjects, found that men ejaculate more quickly and with more volume and motile sperm when it’s a novel subject -- aka a complete stranger. And guess what’s full of novel subjects? Well, at least in erotic digital or print form (unless you’re Steve Stifler): those little rooms in fertility clinics chock-full of porn.  

“It could be when they’re with their partners trying to conceive that there are less sperm," Sirot said, "or they’re less motile.  And when they go into the clinic and are provided with pornography and any novelty stimulus, that they could be producing a different -- and actually transferring a better -- ejaculate.”

In other words, a complete stranger has a better chance of literally extracting better baby-making juices from a man. This is good news for people who are trying to conceive, but it could also mean that the best place to quite literally do it may not be with each other in the bedroom. Introducing new, sometimes X-rated factors (not of your actual partner), could be the most effective way to get the best sample. 

“If you're trying to understand why a couple is having trouble conceiving," Sirot said, "then you need to be collecting ejaculate in a scenario that is as similar as possible to their actual conception attempt.You can't put them in an entirely different situation and assume the ejaculate you get is the same they will get when they're having sex with their partners.”

It doesn’t mean men are born to cheat 

Naturally, the first thing that could come to mind with these findings is that men are instinctively drawn to sleep with other women. We admit it, we thought that -- even though it would mean everything that happened in The Affair was just… human nature? Blasphemy. 

Rest easy. According to Dr. Sirot, that’s complete and utter BS. 

“No, I hate that,” Sirot said. “I have to use my professor speak here, but the only thing we speculated about that is that our results are consistent with the hypothesis that in our evolutionary past men had opportunity for extra-pair populations. It doesn’t mean men are selected to mate with new females, and mate with lots of females, that’s not at all what our results mean.”

It does mean that a one-night-stand could be more favorable for conceiving 

Tinder loyalists, beware. Your night games could be considered a fertile playground.  

“We simulated a one-night-stand more or less, so it does suggest that maybe men would transfer a different ejaculate in a one-night-stand than in a long-term relationship,” Sirot said.  “But the conception also depends on how the female's body is responding, whether she is receptive to the sperm, where she is in her ovulation cycle -- there are so many other factors that affect conceiving.”

Breathe a sigh of relief, guys. Remember: it takes two to slam dance. 

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Liz Newman is a freelance writer for Thrillist and is pretty sure this study is the modern-day equivalent of Fatal Attraction, aka it will scare the bejesus out of every guy in America. Follow her on Instagram and Twitter: @lizn813