We have all been there: you go on a date with a special new someone, and after some potentially awkward moments, you lean in and go for the kiss.  How was it?  Did his/her kiss set your synapses ablaze with thoughts of romance and/or an immediate desire for nudity in close proximity to that special person?

  Despite all the knowledge you’ve accumulated telling you that true love requires time, did you find your inner voice saying “this is the one!”

If so, I may have some bad news for you.  That kiss may be lying to you.

So what is behind this shocking deception?  It isn’t your date’s “game.” (Sidebar: if your date has a noticeable “game”, they aren’t a terribly good long term prospect anyway.)  It’s your MHC.

At this point, you may be saying to your screen: “what the hell is MHC, and why is it trying to screw up my love life?”  Well, MHC is an acronym for a hormone known as the “major histocompatibility complex”, and it isn’t a villain.  MHC is secretly one of the best date screeners you have at your disposal.  Better than your own most logical, introspective self-analysis, better than your smartest, most objective friends, MHC tells you something essential through something as simple as a kiss.

MHC is basically a hormonal breakdown of your entire immune system.  When you kiss someone, you are secretly exchanging essential information with the other person about your immune system.  As humans, we are biologically driven to find someone one with complementary MHC to ours.  By doing this, we increase the immune systems of potential offspring by providing them with the most well-rounded immune system possible.

Think of a kiss like choosing a partner for trivia night down at your local pub.  You want to find a person whose knowledge is in all the areas you lack.  If you’re good at entertainment, literature and science, then you want to find someone who knows history, geography and math.  That’s what your MHC is supposed to do, help you find someone who has immunities to all the things that you don’t.
So if MHC is supposed to do all that for you, how can that first kiss possibly lie to you?  The problem comes down to a little white pill, one so popular and common that it is known as “the pill”.

That’s right, the omnipresent female contraception method known as “the pill”, which surely stands as one of the greatest inventions of the 20th century, has a funny side effect.  It completely screws up your MHC.  So instead of trying to find someone whose MHC complements theirs, ladies find themselves more attracted to men with the exact same MHC.

How important is this problem?  Many sociologists believe that the huge spike in divorce rates starting in the 70s is at least partially due to “the pill” becoming widely used.  Many couples that met while the lady was on it, then married, faced a problem when they decided to have kids.  When the women went off the pill, their MHC suddenly discovered that the partners weren’t hormonally compatible.  Their kiss was suddenly giving bad news.

Before you worry too much, this doesn’t mean that every couple who meets when the girl is on the pill is doomed.  It just means you may be biologically fighting uphill.

What’s in a kiss?  Maybe everything, and not for any of the reasons you thought.*

Blue Sullivan is the author of the wonderful, recently-released dating advice book, Your Ex-Boyfriend Will Hate This, available via Amazon here: http://www.amazon.com/Your-Ex-Boyfriend-Will-Hate-This/dp/1680580442