The 5 Weirdest Reasons We Have Sex (According to Science)

#2. Why Do We Have Sex at All? To Fight Parasites (Duh)

Let's face it: Sex is about as intuitive as shoving a summer sausage into a Georgia O'Keeffe painting. If mankind had to start all over from scratch, we're not so sure we'd figure intercourse out the second time around. There are, after all, major disadvantages to sexual intercourse. The opportunity to contract and transmit diseases, for one. And for another, think of all the energy and resources that go into courtship. It's not like Olive Garden meals are going to pay for themselves, you know.

"So ... the grilled sausage comes with the clam side in a light creamy sauce? This menu is weird."

Compare that to the ways that some far stupider animals reproduce. For example, aphids don't need boys at all -- the girls just fart out clones of themselves every 10 minutes or so. Some starfish just have to shed a limb to make a baby. OK, maybe that's not the best example of a better way to do things. But it's definitely simpler.

Everyone wants efficiency these days, but no one wants to pay the price.

So why didn't humanity take a different turn -- one where we kept the species going by just cloning ourselves? Why can't we and other sex-having species just squirt out spores from our orifices and call it a day?

The Theory:

The answer is that sex -- the mingling-of-fluid kind -- results in constant adaptation. Every kid is carrying the best of her mom, her dad, her grandparents and their lovers. Every one of us is a mess of genetic material coming from all over the place. And that's good, because change is what keeps us ahead of the game when it comes to our biological enemies.

Also because your family isn't really your type.

According to the Red Queen hypothesis, we have to keep adapting to keep moving forward. The theory comes from a scene in Through the Looking Glass when Alice and the Red Queen race but never move. The queen says, "It takes all the running you can do, to keep in the same place."

"And if you're running on a road made of wind and purple, then you're tripping out just the right amount."

Likewise, humans are in a kind of arms race with every other species, especially the ones that matter to us most: parasites. Animals who reproduce asexually never get a chance to mix things up -- to come up with new and better combinations of genes for the next generation. That makes them more vulnerable when a parasite comes along.

"I am become machete! Fuck worms!"

Scientists have even proven the Red Queen theory in the lab. No, not by hosting a couple and watching them breed, then comparing their medical weaknesses to a family of human clones. They just used a particular bacteria and its viral parasite. The nice thing about bacteria is that you can watch hundreds of generations evolve over a short amount of time. So they took one bit of bacteria and isolated it from its parasite partner. Then they took another bit of the same kind of bacteria and let it co-evolve with its parasite, just as it would in the wild.

"Yes, yes, that's it. Now show your flagella."

Five minutes and thousands of generations later, the second group had evolved twice as fast as the first, with more mutations and diversity. Then, just to be mean, they took the virus from the second group and infected the isolated bacteria with it. The bacteria was annihilated. If we didn't have sex, that bacteria would be us every time we came across a new cold.

#1. The Female Orgasm: The Happiest Accident


The male orgasm might be a little messy, but at least it makes sense. Everything about the process of ejaculation is geared toward either human-making or keeping the tissue industrial complex going. God knows we need both if we want to continue as a species. But the female orgasm is a different (cleaner/sexier) animal. The only thing anyone gets out of a female orgasm is a good time.

And blowjob leverage.

So, as a quick review, there are two kinds of lady orgasms. The rare kind is vaginal, the regular kind is clitoral. When you hear the term "G-spot," they're talking about vaginal orgasms (on the inside). Between 70 and 80 percent of people of the female persuasion get their orgasms via clitoris (on the outside).

Supply your own genital metaphors here. We're tapped for the year.

So experts have proposed all kinds of theories to answer the question of why women have orgasms at all. Like that the contractions are supposed to suck sperm toward the uterus and that orgasms are supposed to exhaust women so they'll stay horizontal, so gravity will help sperm hit its mark. But one theory stands head and more head above the rest.

The Theory:

The clitoris is the remains of what would have been a penis. You might even say it's a pre-penis.

Or preenis.

According to biology professor Dr. Elisabeth A. Lloyd, there is zero evolutionary purpose for the female orgasm. Zero. It does absolutely nothing for procreation, nothing to advance the species. But the reason women have them is the same reason men have nipples -- leftovers. Here's the idea: We all start out as sexless tadpoles in the womb. Before the boys become boys and the girls become girls, the basement starts developing nerve and tissue pathways in the exact same places. Then God gives us our assignments and we start our path to Gendertown. But that order -- nerves first, genitals second -- is the reason women get to share in the goodness of orgasms. And maybe why the clitoris looks like it does.

You should probably get this checked out.

In other words, gentlemen, the lady you're boinking is sporting a baby penis, despite her constant protestations to the contrary.

Kristi Harrison is blushing her head off at Twitter and Tumblr right now. You can follow her if you want.

For more on sex that'll turn you away forever, check out 9 Awesome Places to Have Sex (And the Horrific Consequences) and The 10 Most Terrifying Guides to Sex.

And stop by LinkSTORM because sex.

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