Sex is a part of life — and a subject of scientific research. This year was particularly sultry, with studies covering everything from hormone-triggered masturbation to our species' history with Neanderthal nookie.
Here are the top 10 science studies that made us blush in 2012.
1. Masculine hormone gets women interested … in masturbation
High testosterone is often associated with a strong sex drive, thanks to the hormone's link to masculinity. But it's not so simple. A study published this May in the journal Archives of Sexual Behavior found that in women, high testosterone was associated with a greater interest in masturbation, but less interest in getting busy with someone else.
The reason may be that solitary desire, which leads to masturbation, is different than the kind of desire that leads people to proposition a partner, study researcher Sari van Anders of the University of Michigan told LiveScience.
"When you're feeling sexual desire for a partner there might be other factors that play into that, for example, how you felt about that partner that day, how attracted you feel to that partner, how attractive you feel to that partner, your relationship and things like that," van Anders said. [10 Surprising Sex Statistics]
2. Should dudes dominate in bed?
It may not be a good idea to stick to traditional gender roles in the bedroom. Young adults who say men should take charge in bed feel less confident in sexual situations than their more flexible counterparts, according to a study released in October.
The young adults with more rigid gender roles were also less likely than others to take female condoms from a bowl labeled "free," a fact that worries researchers because female condoms are a form of STD and pregnancy protection that women can control.
3. Guys get judged for "too much" sex
Women have long faced judgment for having casual sex, but modern-day college students are likely to judge the genders relatively equally. A study of 19,000 college students found that while only a minority of students judges women more harshly than men, young people still do judge people for having sex with "lots of people."
The survey found that 49 percent of students judged others for their sexual exploits equally regardless of gender, while 12 percent judged women more harshly than men. Another 13 percent judged men more harshly than women. Meanwhile, 27 percent made no judgments at all.
4. Gym orgasms are real!
Who needs sex? Researchers reported in March that the phenomenon of "coregasms" is real. These are orgasms caused by exercises that tense the core abdominal muscles — in other words, gym-friendly orgasms, no genital stimulation required.
In 1953, sexologist Alfred Kinsey and colleagues reported that 5 percent of women reported orgasming from exercise alone. Now, Indiana University researchers have interviewed 124 of such women and found that 45 percent report orgasming in response to ab exercise such as crunches. Another 19 percent linked their orgasmic experiences to biking.
5. Talking about sex: good for sex
Here's a surprise: Communicating about sex during sex may improve sex. The more comfortable you are talking about sex — no blushing! — the more satisfied you'll likely be with your sex life, according to Cleveland State University researchers.
If words aren't your thing, don't worry. The study, published online in August in the Journal of Social and Personal Relationships, found that nonverbal communication such as moaning or coy looks was more connected to satisfaction than getting chatty during sex.
6. New moms aren't sexless stereotypes
Women who have recently given birth are often interested in sex before the typical six-week "all clear" to engage in intercourse from their doctors, a study published in June found. What's more, the likelihood they'll be interested in getting busy depends more psychological factors than physical ones.
Sexual desire returns to pre-pregnancy levels by three or four weeks after the physical ordeal of birth, with the biggest boost among women who felt close and intimate with their partners. These emotional factors appear to make the difference — body image, fatigue, vaginal trauma from birth and breast-feeding weren't linked to how quickly new moms started having sex again.
7. Arousal dampens disgust
If you're feeling grossed out, try spinning yourself a sexual fantasy. Turns out, sexual arousal diminishes disgust. Researchers asked 90 straight women to complete gross tasks, such as sticking their hands into what appeared to be a bowl of used condoms (ick!). But before they did, a third of the women watched an erotic film.
The women who'd seen the sexy movie were less disgusted by the gross activities that followed, the scientists reported in September in the journal PLoS ONE. These findings are important, given that disgust may play a role in some sexual dysfunctions.
8. Sex can be a real headache
A headache can prevent sex, but what about when sex causes a headache? This condition is called "coital cephalgia," and it got attention this year thanks to an article in the British newspaper The Daily Mail.
No one really knows why some people experience headaches with sexual arousal, but men are three to four times more likely to experience the pain than women, according to the British Journal of Medical Practitioners. Migraines are another risk factor. Fortunately, the headaches can be treated with drugs taken prior to getting frisky.
9. Human and Neanderthal hookups are hard to prove
Early humans weren't so species-specific when it came to sex, finds research out in November. The genetic analysis suggests that except for sub-Saharan Africans, every population on Earth has a little Neanderthal in the family tree.
These genetic traces could be a sign that humans and Neanderthals had sex after humans migrated out of Africa about 100,000 years ago. Or it could mean that an ancestral group to both modern humans and Neanderthals split from the rest of Africa much earlier and stayed separate until leaving the continent thousands of years later.
The second is a more complex scenario, but proving the first beyond a shadow of a doubt is tricky, as a recent American Journal of Physical Anthropology study highlights. That research finds interbreeding between monkey species leaves few genetic marks, meaning that, if anything, hybridization is often underestimated.
10. Extra 'X' boosts male sex drive
Girly guys, rejoice: An extra female chromosome could boost your sex drive.
Okay, the research is in mice. And having three sex chromosomes has a number of unpleasant side effects in humans, such as reduced fertility. But the study is an intriguing look at how sex chromosomes influence behavior.
Men have both an X and a Y sex chromosome, while women have two Xs. In some cases, genetic mistakes in development result in males with an XXY genotype, called Klinefelter's syndrome in humans. Mice with this genotype mount females more often, pelvic thrust more vigorously, and ejaculate twice as fast and nearly twice as often as XY male mice, according to a February study in the journal Hormones and Behavior. Whatever the reason, it was not hormone levels, as these mice showed no differences in their sex hormones. Researchers still need to do more research to find out if the results would hold up in other mammals.
Follow Stephanie Pappas on Twitter @sipappas or LiveScience @livescience. We're also on Facebook & Google+.
