5 Scientific Explanations for Your Sexual Perversions

5 Foot Fetishes Kept Us Free of STDs

Looking to warn your kid away from sexually transmitted diseases? Try encouraging him to lust after feet. No, that isn't an excerpt from our parenting guide, So You're Stuck With a Baby: Tips for Making It Interesting. It's actually a sound theory based on some pretty badass science.

Feet are the most fetishized body part out there. There's no obvious reason why -- it's not like, say, a leather fetish, where everyone can look at Catwoman and say, "Yeah, I get that." You can't have sex with feet, and even if you could, would you want to? A lot of fungus lives there.

Well, scientists wanted to know why, so they started digging. First of all, how did it get started? There are several theories, including one from an expert who says that sensation in the feet and genitals both transmit to the same area of the brain, so there could be some accidental crossover there. But why would it persist through thousands of years of evolution? The answer appears to be disease.

Researchers collected history's records of foot-lust and compared it with the greatest STD outbreaks of the last thousand years: gonorrhea (the 13th century), syphilis (the 16th century, with an encore in the 19th century) and AIDS (the break-dancing years up to now). Scientists learned two things. The first was a greater appreciation for antibiotics, and the second was that foot fetishes are most prevalent in times of disease.

In other words, when our genitals know it's too dangerous to go outside, we start fantasizing about toes and bunions and the way sneakers smell. To test this theory, an intrepid band of sex researchers looked at the prevalence of feet in eight major pornographic publications from 1965 to 1994. Then they made a graph, because graphs are what get scientists off.

It's worth noting that a general obsession with feet also correlated with periods of greater female power, as if women themselves were taking away the usual goodies and substituting the third filthiest part of their bodies instead, just to show men what was what.

4 Oral Sex Helps Prevent Miscarriages

The nice thing about oral sex is all of it. No one gets pregnant, people who are virgins can stay virgins when they do it and according to the '90s, it doesn't technically count as sexual relations. Win-win-WIN. So it's easy to see why humans and animals and all things with genitals engage in oral sex in the first place. What's not so obvious is the evolutionary value of the act. It doesn't pass on the genes. And what do women get out of going downtown, other than an occasional free pass later on in the month?

If Dr. Gustaaf Dekker is to be believed, she gets the benefit of safer future pregnancies ... but only if she swallows.

Among other things, there are unique proteins in every man's sperm, and the more "familiar" a woman is with her partner's semen, the more likely her uterus is to accept it when it's time to procreate. And according to science, or this scientist, anyway, the very best way to get familiar with your future mate's manseed is to digest it.

Dekker also found that pregnant women who practiced oral sex were less likely to have preeclampsia, a condition where the woman's immune system rejects her own placenta, presumably because she's less likely to recognize the fetus as a foreigner. Dekker puts it this way:

"If there's repeated exposure to that signal then eventually when the woman conceives, her cells will say, 'We know that guy, he's been around a long time, we'll allow the pregnancy to continue.'"

Here's a hint to teenage boys everywhere: This is not the message you want to pass on to your girlfriend in the back seat of your car.

3 Multiple Orgasms Exist to Encourage Freaky Group Sex

We've previously speculated that the female orgasm was strictly a leftover of evolution, that the clitoris is wired to feel good during sex because it's really a pre-penis. But there are other theories about the purpose of the female orgasm out there as well. Such as the one about how orgasms are merely an award for getting freaky with multiple partners. And why would a woman want multiple partners? So none of them would murder her babies.

According to one anthropologist, and also anyone with sexual experience, the female climax is a completely different animal from the male's. For one thing, it's harder to achieve. And for another, lots of women can have lots of them at once ... just over and over again. Men can't do that.

So Dr. Sarah Hrdy speculates that the orgasm was once an incentive for women to keep on mating once their first, or second, or third partner was done with his business. Because if she mated with lots of guys at once, none of them would know who had fathered her children. Which meant that killing off your rival's kids was impossible -- because they could be your kids. You Game of Thrones fans know what we're talking about here.

Dr. Orgasm's theory is backed up by observations in the animal kingdom. Langur monkeys are relatively (for monkeys) monogamous, and dominant males are all about infanticide in order to secure their rank as alpha male, and also to make the mom stop producing milk so she can mate again. And also because adult langur monkeys are monsters.

But you don't find that behavior among macaques and chimpanzees, or at least not nearly as much. And sure enough, the difference is that macaques and chimpanzee females bone lots of different dudes. So, the female orgasm may very well be evolution's reward to women for hosting nasty ape sex parties.

2 We Kiss to Get Close Enough to Detect Pheromones

In this article, we explained the theory that kissing evolved as a way for women to expose themselves to cytomegalovirus so their future babies wouldn't get hit with a herpesesque disease in the womb. And man, is that the most unromantic explanation for kissing EVER. The good news is that there are other, less awful theories about smooching out there. One is that we've all got a secret sex nerve in our brains that compels us to swap spit.

But first, some background. Everyone has 12 pairs of nerves jutting out of the brainstem, appropriately named Nerve I through Nerve XII. And most of them are regular sensory nerves, like the olfactory one and the optic one and the one that helps us see the dead. But in 1913, scientists discovered another nerve that everyone had missed before. "Nerve 0" (or, as we like to call it, Nerve Oooooh) sits at the base of our skulls, seemingly useless, like a third testicle on an already sterile old man. So it's not surprising that everyone kind of forgot about it.

So when scientists finally got around to figuring out what this nerve did, they discovered something funny. Even though it looked like an olfactory nerve, it was present in creatures that had long ago lost their sense of scent. Which means it must have some purpose in humans (and all other animals) besides making public transportation unpleasant. Shortly thereafter, scientists discovered that cutting this nerve caused mice to stop breeding.

It turns out Nerve 0 is directly connected to the regions of the brain associated with sex and gives your nose a direct, private highway to your genitals. Well, that's interesting. What could that be for?

Scientists theorize that when you kiss someone, Nerve 0 picks up their pheromones and warns your body to start sending blood and good vibes down to your crotch as quickly as possible. It's important to note that Nerve 0 doesn't travel through your olfactory bulb at all, which means you can't actually smell any of the things your sex nerve is designed to pick up. And since our pheromones don't carry very well, getting close enough to kiss is basically the only way your Boning Nerve can do you any good.

And what kind of things does your brain learn by picking up pheromones this way? For one thing, it allows you to sneak a peek at your lover's immune system. People you're attracted to will tend to have been exposed to very different antibodies over the course of their lifetimes. This ensures that you have a lower chance of miscarriages and a higher chance of birthing superbabies with badass immune systems. It also stops you from finding your relatives sexually viable, so let's give it a round of applause for preventing a lot of awkward family reunions.

1 Big Boobs Exist Thanks to the Missionary Position

Here's a question we bet you never asked yourself: Why do guys prefer big breasts? Don't say it's because it signals that a woman is more capable of nursing -- huge boobs serve no practical purpose for the delivery of milk. Well, according to one theory, it has to do with our ancestors preferring face-to-face sex.

The humble "missionary position" has the unfair reputation of being the boring option for couples too tired to try anything too crazy. But out in the animal kingdom, that position is crazy -- face-to-face sex is something of a revelation for mammals. Our ape ancestors preferred a much less ... frontal method. But the pair bonding that occurs when couples look each other in the eye while doin' it is beneficial enough to humanity that evolution favored people who had face-first sex.

In The Naked Ape, British zoologist and ethologist Desmond Morris proposed that the social benefits to our ancestors who liked missionary-style sex were great enough that evolution favored frontal features that mirrored the backside. Namely, giant breasts that mimic the bulbous buttocks of our great-to-the-power-of-500 grandmas. As Desmond put it:

"The protuberant, hemispherical breasts of the female must surely be copies of the fleshy buttocks, and the sharply defined red lips around the mouth must be copies of the red labia."

Of course, Desmond, they must be. And that means that big breasts exist purely to compel attention. In other words, evolution masterminded the single most successful advertising campaign in world history.

Robert Evans oversees the image captions at Cracked and has a blog where he writes letters on our messed-up justice system, illegal immigration, oil drilling and drug policy to the conservative parents of the world. If you'd like to hire him, he can be reached at revanswriter@gmail.com.

For more science behind human actions, check out 6 Obnoxious Old People Habits (Explained by Science) and 6 Factors That Secretly Influence Who You Have Sex With.

And stop by LinkSTORM to discover which columnist won't leave people's feet alone.

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