Scientists Find Sisters Make Male Rats Less Sexy; Gyllenhaals Suggest Otherwise

Illustration for article titled Scientists Find Sisters Make Male Rats Less Sexy; Gyllenhaals Suggest Otherwise

A new study shows that male rats raised with lots of sisters are less attractive to lady rats. So is this research applicable to humans?

According to the Association for Psychological Science (via Good Men Project), researchers at UT Austin found that male rats raised in litters with lots of female rats excited less interest from potential mates. How do you know if lady rats like a dude rat? Study author David Crews explains that "if they want to mate with a male, they'll do a move called a dart-hop." Also, "they wiggle their ears. It drives males nuts." Hot. Males from female-dominated litters inspired less dart-hopping, but they may have made up for this by being quicker on the draw — while they penetrated and ejaculated in female rats as much as their counterparts raised with fewer sisters, they spent less time "mounting." I'm not totally sure what constitutes good rat sex, but it kind of sounds like these dudes were eliminating foreplay.

Writes Lu Fong of the Good Men Project,

So does this translate to humans? Not exactly. While sibling studies have shown that having sisters could prevent depression — and having an older brother often sparks more aggression — there's no direct correlation between our species … yet.


In fact, I would think the opposite would be true in humans. I can think of several reasons why dudes with sisters might be more attractive than average. They're less likely to be grossed out or confused by periods, for instance. They're less likely to subscribe to the two most obnoxious dude myths about PMS — a) it is fake, and b) it is responsible for all women's anger, ever. Most importantly, they have some early experiences interacting with girls around their age in a nonsexual context, which may help them respect women and treat them as equals later on. In general, getting socialized with people of other genders is probably good for all humans — regardless of what lady rats think.

Too Many Sisters Affect Male Sexuality [Association for Psychological Science]
Having Sisters Could Kill A Guy's Mojo [Good Men Project]

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Okay. I know a weird amount of information about rat gestation thanks to strange classes my college offers, so I thought I would add to the discussion through some explanations of the biotic features of rat pregnancies.

(This is totally normal, you guys.)

Rats, obviously, deliver babies in litters. However, they don't have a separate hormone streams for each individual pup. Rather, they have vaguely directed hormones that go kind of in the right direction. If a male rat fetus is lower in the hormone stream than a bunch of sisters, he gets the remnants of all the female hormones. In his later life, he is more likely to exhibit female sexual behavior. The same is true of females but in reverse.

This biological element is not true of humans because we are born singularly. Even if you have a twin, you have a separate bloodstream.

This research is interesting because they switched up the mostly-male biological litters with the mostly-female biological litters, skewing them to have mostly males, mostly females or an even mix.

That wasn't really going anywhere. I just happen to really like rat hormones.