Here's a message for people who have sex with people with vaginas, brought to you by Charles Darwin: Go down on your goddamn partners already.
There are plenty of reasons why couples should be indulging in as much cunnilingus as a person wants, not limited to the fact that it's just common courtesy. It's not simply because the orgasm gap is alive and well and oral sex is a great way to close it, or because plenty of dudes enjoy giving head.
It's really much simpler than that: Women might have evolved to stay with partners who eat pussy, Medical Daily suggests.
While it's hard to pin down a single evolutionary reason why humans engage in oral sex, scientists have come up with a few possible explanations for why we lick each other's privates. When it comes to fellatio, for instance, research has shown that swallowing semen could potentially reduce preeclampsia, a life-threatening pregnancy-related condition. This can, in turn, boost chances of successfully carrying a pregnancy to term, which has obvious benefits for the species.
The story is (perhaps unsurprisingly) a bit more involved for cunnilingus, though. Although it's clear oral sex can heighten arousal and, as a result, overall sexual satisfaction, it's not entirely clear what role that might play in perpetuating the species.
However, as Medical Daily notes, a 2013 study of 243 men in long-term heterosexual partnerships indicates that women's sexual fulfillment could have a great deal to do with their decision to maintain one sexual relationship instead of pursuing another:
The research showed that men who were most likely to report getting their partner to orgasm during oral sex were more likely to think their woman was sought after by other men. Therefore, the more eager men are to please partners believed to have better options the more likely they may be to perform cunnilingus to keep their mates from cheating.
Basically, the hypothesis goes, if women are getting off enough with their current sex partners — which is more likely to happen when their getting plenty of (good) head — they might be less likely to cheat.
Of course, there are many different reasons why people might be unfaithful, not to mention many different ways to define "cheating," none of which necessarily have to do with sex. Still, on a list of things that might make a person more likely to re-think having sex with someone else, having a partner who loves performing oral sex (or generally trying to ensure sexual pleasure) isn't the worst reason to stick around.
Well, unless the other person is even better at giving head. In that case, it's only natural.