science The Scientific Reasoning Behind Our Strange Sex Practices  

David Sharp
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Let's face it, sex is weird. And gross. And the reason you exist. And the driving force behind the world's technology. And you love it, don't you, you filthy, filthy pervert?

Human beings have developed some very strange sex habits, and it's easy to look at something like, say, nasolingusts (nose lickers) and wonder, simply: why? But the science behind sex practices is actually fascinating.

The oft-repeated "Rule 34" states that for every action there is an equal and opposite porn version of that somewhere on the Internet. If that's so, then Rule 35 states that for every sexual quirk and preference, there is also a team of scientists studying that exact quirk on lab rats and college students.

We've come a long way since the days of Alfred Kinsey and this article looks at all the best guesses about what's happening down there from today's top biologists, psychologists, sociologists, and dominatrixes. After examining the science of sex, it turns out our sex practices may not be so strange after all; there's generally a very reasonable scientific rationale behind why you like what you like. Not that you're not still a disgusting monster, just that you've probably got company. 

We Kiss to Ensure Our Mates Are Capable of Raising Children


We Kiss to Ensure Our Mates Ar... is listed (or ranked) 1 on the list The Scientific Reasoning Behind Our Strange Sex Practices
Photo:  MadalinIonut/Pixabay/CC0 1.0

According to Smithsonian philematologists (scientists who study kissing), when we kiss, we exchange 9 milliliters of water, 0.7 milligrams of protein, 0.71 mg of fats... and somewhere between 10 million to 1 billion bacteria. So why do it? Why expose yourself to the risks of orifice-to-orifice contact, which include disease, infection, beard burn, and tasting someone's bad breath?

Well... science is still working on that one. One of the confounding things is that kissing is not a universal human trait - it's a relatively novel practice, evolutionarily speaking, and there are plenty of cultures that do not engage in romantic or sexual kissing. This suggests that it is more of a learned behavior than anything hardwired into our circuitry. The most likely explanation seems to be that kissing is a strategy for testing a potential mate's genetic code.

Women particularly favor kissing, and especially during the early stages of a relationship, with the thought being that if a partner tastes bad to you it's less about what they had for lunch and more about searching for signs of disease, genetic imperfections, and detecting little guys called major histocompatibility complex genes.

Humans are capable of tasting and even smelling MHC genes, which can indicate just the right amount of biodiversity in order to optimize your chances at having a healthy baby. So maybe Betty Everett was more right than she knew when she told your grandma "it's in his kiss."

This will also explain more. 

A Fixation on Breasts Is Indicative of a Desire to Find a Reproductively Viable Mate


A Fixation on Breasts Is Indic... is listed (or ranked) 2 on the list The Scientific Reasoning Behind Our Strange Sex Practices
Photo:  TheresaOtero/Pixabay/CC0 1.0

To say that men have historically displayed an interest in breasts is perhaps a historical display of understatement. The question, however, is "Why?" Why do these seemingly innocuous deposits of fat above a woman's pectoral muscles hold such a sway over so many men?

The prevailing theory is that breasts are a good indicator of female fertility and reproductive health. They are a signpost literally sticking out at members of the opposite sex, drawing attention to the fact that the bearer of said boobs is of a sexually viable age, that she is nutritionally advantaged, and perhaps even suggesting what part of her reproductive cycle she may be in. 

Another theory is that fetishizing breasts is just another case of partialism (a fetish that applies only to a specific body part). We associate breastfeeding with pleasure at an early age, and that flood of feel-good chemicals becomes associated with that otherwise non-sexual organ. Women may also cross-associate nipple stimulation with sexual desire because oxytocin - a neuropeptide that has been shown to increase feelings of relaxation, attachment, and trust - is released during both breastfeeding and orgasm.

Penis Size Is Only Important in Relation to Physical Compatibility


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Photo: The Shared Experience/flickr/CC-BY-NC-ND 2.0

Ladies and gentlemen, the results are in, the debate is over, and we can say conclusively that in the case of Boat Size vs. Ocean Motion, penis size totally matters. Sometimes. To some women. In short: it depends. Some women do clearly favor large anatomies. Others do not. And are we talking length or girth?

Turns out, penises are different, vaginas are different, and people's physiological and psychological makeups are different - so you're just going to have to buckle down and figure out the combination that works for you. It'll be a rough period of trial and error, but hopefully, you'll be able to handle the workload. Until then, here are some helpful stats about wangs: the average penis length is about 5.56 inches, the average penis girth is 4.59 inches, 58 percent of newborn males are being circumcised (and that number is dropping), and here's a list of some dumb things that penises have been called.

We Like Big Butts Because They Show a Woman's Ability to Handle Pregnancy


We Like Big Butts Because They... is listed (or ranked) 4 on the list The Scientific Reasoning Behind Our Strange Sex Practices
Photo:  Jason Staten/via Flickr/CC BY-NC-ND 2.0

We all know that big butts are powerful enough that they can render some men incapable of lies, but just what is it about having a great big round thing in one's face that gets men so sprung? Similar to the breasts, a trunk that is optimally packed with junk (aka gluteal-femoral fat) can be an indicator of genetic health and sexual maturity. Studies have also shown that women with a little more bass tend to be more intelligent and more resistant to chronic illness - no word on whether any of those studies were funded by the Trainor Institute for Bringing Booty Back

Current research indicates that it's not even so much the butt itself that we are interested in but the alignment of the spine and hips. Women shift their center of mass backwards during pregnancy to compensate for the extra baggage up front, and what men are really looking at is their body's capacity to handle that shift. A woman with greater "vertebral wedging" was deemed more capable of staying healthy during pregnancy, surviving multiple pregnancies, and rolling in Sir-Mix-a-Lot's Mercedes.

See what else does the trick here.