10 Things You Probably Didn't Know About Love and SexS

Regardless of your stance on Valentine's Day, there's no way to avoid being bombarded with romantic imagery. So you might as well take this as an opportunity to learn something new. With that in mind, here are ten things you probably didn't know about sex, love and lust.

Illustration from Saga, by Fiona Staples.

Who knows? Maybe you can use one of these to impress your valentine — in fact, some of these could probably even be crafted into clever pickup lines.

10. You can break a penis

10 Things You Probably Didn't Know About Love and Sex

There are no bones in the penis, but it can, in fact, become "broken." Doctors refer to the injury as a "penile fracture," and it's every bit as harrowing as you'd imagine. (All right, so if you're going with the whole pickup line angle, you might not want to start with this one.)

"[Penile fracture] is a severe form of bending injury to the erect penis that occurs when a membrane called the tunica albuginea tears," explains Hunter Wessells — chair of the urology department at the University of Washington School of Medicine. He continues:

The tunica albuginea surrounds the corpora cavernosa, specialized spongy tissue in the core of the penis that fills up with blood during an erection. When the tunica albuginea tears, the blood that is normally confined to this space leaks out into other tissues. You get bruising and swelling.

So how does a penis actually, you know, break? According to Wessels, any form of vigorous intercourse when the penis is rammed into a solid structure... "during sexual acrobatics," for instance.

"We had this patient who suffered penile fracture after running across the room and trying to penetrate his wife with a flying leap," he says.

9. Ovulating strippers make more money (according to one poorly conceived study)

In 2007, researchers at the University of New Mexico recorded a surprising correlation between strippers' ovulatory cycles and their tip earnings. Strippers who were ovulating (and thus most likely to conceive) averaged $70 per hour in tips. Those who were menstruating, and those who were neither menstruating nor ovulating, pulled in $35 and $50, respectively. One hypothesis for this strange observation is that men are, subconsciously, more inclined to tip a woman who they believe they have a better chance of producing a child with.

But take all of this with a grain of salt. The investigation monitored a mere 18 dancers from one club for a total of two cycles, making it more than a little limited in scope and its sample size borderline ridiculous. Needless to say, few were surprised when Geoffrey Miller, the researcher who conducted this study, was reprimanded by his university last year for lying about his research in other areas.

8. Women can smell genetic incompatibility

10 Things You Probably Didn't Know About Love and Sex

The genes that comprise your major histocompatibility complex (MHC) play an important role in regulating your body's immune response — most notably in determining compatibility of donors for organ transplant. Some data have shown that the more dissimilar a man and woman's MHC are, the more likely they are to bring a child to term — but even more interesting is that women are thought to be capable of actually smelling this genetic differences.

In a study led by Claus Wedekind at the University of Bern in Switzerland, women were asked to smell T-shirts that had been worn by anonymous men for two nights and choose ones which appealed to them. According to the researchers, the women consistently preferred the odors of shirts worn by men with dissimilar MHCs.

How the whole smelling thing works remains very much a mystery. Research has shown that mice detect compatibility genes by smell, as do some species of fish. But in an interview with The Guardian, researcher Daniel M. Davis, author of The Compatibility Gene, admits that, at least for humans, "how [MHC detection] works on the olfactory level is basically not understood at all."

7. Birth control could mess with a woman's ability to assess a mate

In the study conducted by Wedekind and his colleagues, the womens' preference for men of dissimilar MHCs was actually reversed when the women rating the odors were taking oral contraceptives.

6. Fat men last longer in bed

10 Things You Probably Didn't Know About Love and SexS

The relationship between obesity and sexual health is sort of a mixed bag. On one hand, obesity is associated with erectile dysfunction; on the other, studies like this one — published in 2010 in the International Journal of Impotence Research: The Journal of Sexual Medicine — suggest that the fatter a man is, the less likely he is to suffer from premature ejaculation. In fact, men with a higher body mass index (BMI), were able to make love for an average of 7.3 minutes, while slimmer test subjects averaged 1.8 minutes.

So what's the secret behind those extra five and a half minutes? Men with excess fat also pack higher levels of the female sex hormone estradiol. One hypothesis is that this substance interferes with the the body's ability to achieve orgasm... at least for a few minutes.

5. The seven year itch may not be a myth

Originally made famous in the 1955 film by the same name, the phrase "seven-year-itch" is used to describe the tendency for someone to become unsatisfied with their partner or marriage after a period of seven years, at which point they may feel an urge to move on.

If you're measuring by way of divorce, the myth of the seven year itch may not be a myth after all; according to the 2009 U.S. Census Bureau, the median duration of first marriages that end in divorce is 7.9 years.

10 Things You Probably Didn't Know About Love and SexS

4. We will actively avoid temptation

Even if the seven year itch is real, evidence also suggests that men and women will actually avert their attention from tempting alternatives to their partners — even if this aversion is subconscious.

In a study published in 2008, psychologist Jon K. Maner showed male and female test subjects pictures of faces on a computer screen for half a second, followed immediately by a circle or square on some other region of the computer screen, which they were asked to identify by pressing a corresponding keyboard key as quickly and accurately as possible.

The results show that the gazes of single, heterosexual men and women were liable to linger on photographs of attractive members of the opposite sex, in what the researchers refer to as a high level of "attentional adhesion." But the test subjects who were already in relationships reacted differently, and actually looked away from attractive faces more quickly; in fact, some test participants in relationships turned their attention away from "attractive" members of the opposite sex more quickly than they did from "average" looking faces.

10 Things You Probably Didn't Know About Love and SexS

3. Masturbation starts in utero

Those of you flying solo on Valentines day should know that masturbation is nothing to be ashamed of — in fact, there's a chance you've been practicing it since you were in the womb. What you see here is a sonographic image from a paper titled "Sonographic observation of in utero fetal 'masturbation.'" In the image on the left, the baby's hand can be seen hovering above the penis. In the image on the right, the yellow arrow shows the hand engaged in what researcher Israel Meizner describes as "the hand grasping the penis in a fashion resembling masturbation movement."

"Bear in mind," explains Mary Roach — author of Bonk: The Curious Coupling of Science and Sex — at her TED talk on things you didn't know about orgasms, "this was an ultrasound, so [Meizner would have observed] moving images."

Then again, who knows? Maybe there's nothing sexual about this image at all, and it's actually an example of the palmar grasp reflex in the womb. [Figure by Meizner et al. via TED]

2. There's more to the clitoris than you probably realize

10 Things You Probably Didn't Know About Love and SexS

If you picture a clitoris in your mind, there's a good chance that what you're imagining is actually the tip of a bigger, internal clitoral iceberg — a sexual organ that is much larger than the sensitive bundle of nerve endings on the outside of the body (the tiny part of this diagram which is labeled as "Glans") would lead you to believe.

We covered the enigmatic clitoris in greater detail here but the upshot is that prior to the late 90s, researchers had never studied the internal structure of an excited clitoris. In fact, it wasn't until 2009 that scientists produced the first 3D sonography of a stimulated clitoris. The sexual organ is depicted here in its excited state in an illustration by the Museum of Sex Blog's Ms. M, which she drew for this fascinating post on the internal clitoris. Do yourself a favor and go educate yourself.

1. If sex makes you sick, ask your doctor about injecting yourself with semen

Have you heard of post-orgasm illness syndrome, or POIS? It's something entirely different from post-coital regret; it's a rare condition characterized by flu-like symptoms — including fever, runny nose,extreme fatigue and burning eyes — that arise following ejaculation and can last for up to a week. It's basically one of the most unfortunate syndromes on Earth. Ever.

But there is hope for sufferers of POIS. According to two studies published by researches at Utrecht university, men with the syndrome may just be allergic to their own semen, a finding that could open doors to helpful therapeutic options.

In the first study, 88 percent of men diagnosed with POIS were subjected to a skin-prick test (using a diluted form of their own semen) and had a positive skin response indicative of an allergic reaction. In the second study, men diagnosed with POIS were treated with hyposensitization therapy (which is commonly used to treat allergies), which involved exposing the patients to skin injections containing increasing amounts of their own semen. The study revealed that over the course of three years, the men showed a significant drop in their POIS symptoms. (A similar form of treatment has been proposed for women who are allergic to semen.)

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This io9 Flashback originally ran in 2012.