6 Factors That Secretly Influence Who You Have Sex With

#3. The Taste in a Kiss

The Romantic Notion:

"Ah, the kiss, the connection of two souls, the action that binds both young and old lovers for eternity. The romantic tension ... the passion ... the intimacy ... the lust ... the burning desire ... the hunger for more ..."

The smell of an egg burrito and last night's bourbon on your partner's breath ...

Science Says:

There's a cluster of chromosomes present in the body called MHC (major histocompatibility complex) that controls part of your immune system. And when you're out looking for someone to breed with, MHC is probably the most influential aspect of a partner that you didn't know you were judging. MHC controls your ability to fight off infection, and if you breed with someone whose MHC is similar to your own, the pregnancy is less likely to take. Finding someone whose MHC is different means a more diverse immune system for the child.

In other words, evolution supports getting strange with strangers.

In fact, according to a report in Psychology Today, the scent of MHC might be the second-most-important factor in determining how attractive a woman finds a potential mate. While you might not realize you're secretly judging someone you just met on how well your child would be able to fight off a cold, that's what's happening. Your body tries to instinctively make sure that each potential partner has the sexual compatibility seal of approval. Now how does it do that?

MHC is present in both pheromones and saliva, meaning that to really detect whether a partner is suitable, one must be in close proximity (to smell the MHC), and there must be an exchange in saliva (to taste the MHC). Now, what usually happens when these two events are placed together? That's right, ladies and gentlemen -- the kiss is in fact a goddamn taste test. We've adapted the behavior to make sure we find someone with whom our chemicals match up.

"Wow! We both taste like shame."

So all that stuff about loving someone's soul? You could go out and find someone who shares your interests, reads the same manga, orders the same pizza, gets along with your parents and even gets the "subtle intelligent humor" that you (and only you) understand. All it would take is the taste of that person's saliva for that interest to go from "I want to make love to you right now! I don't care if the kids I'm babysitting are watching" to "I like you, but more like a brother."

#2. The Pill

The Romantic Notion:

"If you truly love someone, know him better than you know yourself and want to spend the rest of your life with him, only then should you get married."

Unless he's super rich.

Science Says:

If she's been on birth-control pills the whole time you dated, there's a chance you're both being tricked into marrying exactly the wrong person by your own bodies.

When a woman is actually pregnant, her body decides, "It's not like I can get more pregnant," and it stops doing a bunch of the things it normally does. The pill basically uses hormones to convince a woman's body that it's already pregnant. The woman doesn't want to get pregnant, her body thinks it's pregnant, everyone's happy.

Except for the pacifier industry.

Or at least, they would be if it weren't for that pesky MHC stuff controlling who you can fall in love with. Just as a pregnant woman might find herself suddenly craving food she used to find repulsive, her taste in MHC undergoes a polar reversal. She's no longer attracted to people with MHC that is dissimilar to hers, and way more attracted to men with similar MHC. From an evolutionary perspective, this was probably so that women would want to spend more time around family members in a protective environment rather than out at a bar trying to get laid again. In a modern context, it's probably why pregnant women so often want to murder their husbands with a meat cleaver: He no longer smells like her type, and it's far too late for that.

A woman on the pill gets exactly the same effect, without the belly or the appearance of the boob fairy. For the entire time she's on the pill, a woman will prefer people with MHC that is similar to her own. This is why some psychologists believe that the high divorce rate in modern times can be blamed on the pill. Two people can be dating for years, thinking they're meant for each other when in reality, their MHC is the exact opposite of compatible. Of course, they only find out when they're ready to hatch one and she goes off the pill, which of course is often way, way too late.

Thanks, Syntex. This wasn't on your leaflet.

#1. Timing

The Romantic Notion:

"It's OK, Jimmy -- you don't have to talk to her now. Whenever you get the courage, whenever fate and destiny decide, that's the right time."

And if fate and destiny need a little lubrication? That's where Cutty Sark comes into its own.

Science Says:

Whether you end up getting rejected by someone or falling in love with her can be totally determined by the day of the month you meet her.

Whether a woman wants babies or not, her body definitely does. Every month, a woman's body fires up the baby maker, releasing a fertile egg into the line of fire in case she gets lucky. To help improve her luck, her body also makes sure she looks ripe for the picking by raising the size of her breasts, dilating her pupils and increasing the pitch of her voice. All of this is accompanied by a cocktail of pheromones wafting off her body into the air around her.

"I'm sorry -- you smelled like you wanted it!"

Yes, there is a time every month that each woman is basically signaling to the world that she wants to have sex. How good are men at picking up on these signals? One study showed "that strippers who are ovulating average $70 in tips per hour, those who are menstruating and thus unable to conceive make $35 and those who are doing neither make $50." Women have also reported "that when they're ovulating, their partners are more loving and attentive and, significantly, more jealous of other men."

This means that women who meet Mr. Wrong during ovulation are more likely to sleep with him, and he's less likely to say no. So if Romeo and Juliet had met two weeks earlier, there's a pretty good chance the play would have been called The Capulets Throw an Uneventful Party.

And if the timing had been different in other plays? West Side Orgy.

So ladies, if you're wondering how you keep ending up with jerks, take a look back through your inbox. Do the emails you send your friends about how you "met the greatest guy at the bar last night" tend to fall around the same time each month? It might be because ovulation actually lowers women's standards for sexual partners and even goes so far as to increase their likelihood of sex with multiple partners.

And guys, if a douchebag runs into your dream girl at a sexually convenient time, it might not even matter if he's the type of person who would request a "bridesmaid sandwich" in their wedding vows. He's going to have the edge.

Sami would like to thank Andrew, Kadir and Matt for their inadvertent assistance; Mark M. freelances and dispenses bad philosophy and relationship advice. Follow Kathy on Twitter, befriend her on Facebook or read the rest of her Cracked articles here.

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For more ways to improve your chances of finding true love, check out 6 Ways You Can (Accidentally) Attract the Ladies and 6 Things Men Do To Get Laid That Science Says Turn Women Off.

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