Your Mom and Sisters Don't Want You to Marry Sexy Men Who Are Good in Bed

In Shakespeare's Romeo and Juliet, Lady Capulet attempts to sell Paris (basically one boring dude) to Juliet by saying, "Verona's summer hath not such a flower." Of course, this isn't true. Ancient family feud notwithstanding, Romeo is a far sexier prospective partner.

While it's probably not a great idea to base your dating life on Shakespeare's most famous tale of star-crossed lovers, it's possible that Romeo and Juliet has greater relevance for modern dating than any of us thought. A new study from the Norwegian University of Science and Technology's Department of Psychology finds that mothers and sisters are genetically predisposed to want you to settle down with dull, dependable dudes—but your sister wants to save the funny, good-looking guy who's great in bed for her. To find out about the so-called 'Juliet effect', we spoke to Professor Leif Edward Ottesen Kennair, co-author of the study.

"We start from the assumption that mothers and daughters or sisters share an interest in the wellbeing of their relation. The inclusive fitness theory suggests that as 50 percent of your genes are passed down to your sibling's children, it's important that they do well in life," Kennair explains. Essentially, it's of benefit to you that your nieces and nephews have "superior genes," as Kennair charmingly puts it. "So what we learn is that women tend to seek out partners for their sisters or daughters who provide direct benefits that could be shared for the family in general."

To test his hypothesis, Kennair and his report co-author, Professor Robert Biegler, asked female students and their sisters to rank 133 characteristics that described the perfect partner for themselves or their sisters. Having previously asked mothers and daughters to fill out the same questionnaire, Kennair and Biegler found that the data overwhelmingly supported the same conclusion.

When choosing partners for themselves, women would go for men who were sincere, humorous, charming, fun, and good in bed. When picking for their daughters or sisters, however, they'd perceive characteristics like being understanding, responsible, and sensible as more important. Basically, your mom and sister want you to marry a boring dude who'll never cheat and help you put up shelves. But when it comes to their choices, they'd go for sexy boys who are good at sex.

"What we see is that people go for the more sexy partner for themselves," Kennair says, "but go for someone sensible for their sisters." Is it possible that women don't want their sisters or daughters to go out with fuccbois because they're the ones who'll end up picking up the pieces when it inevitably goes wrong? "I think so, yes. It's more a case of letting her pick up your pieces, as it were."

Of course, we don't need science to tell us that people are irrational when it comes to choosing sexual partners. But is there an element of sibling rivalry here? "Well, if were to believe some comedians, a rich man is someone who earns more than the husband of her sister! So there may be an element of competition here. But the differentials between what women want for their close familial relatives are so specific that it's not so much the case that women want partners with all the good qualities themselves—just some of the good qualities."

But maybe, I suggested, people don't pick sexy partners for their daughters and sisters because we're all weird about the idea of our relatives having sex. "We conducted the study in Norway, which is one of the world's most sexually liberal countries. So I think your suggestion of a general prudishness about sibling sex is relevant, but less so in Norway than any other country I can think of."

On a basic level, we're all just animals just trying to pass on that favorable genetic material to our nearest and dearest. "Lady Capulet wants Juliet to marry Paris, because Paris is rich and has lots of alliances that would help the Capulet family's situation," Kennair says. "But Juliet would do better if her sister married Paris, and she got to pass on the sexy genes of Romeo to her children."

While that particular scenario ended in chaos, the genetic truth remains: Pick the sexy guys who are good at sex for yourself, and save the boring nice guys for your sisters.