Here's How Your Body Knows Who's "The One,"

Surely you remember that fateful day you met the love of your life. What was it that first made you swoon? Was it his sparkling eyes, his sense of humor, or his love of death metal? Despite all the heart-eye emojis in your memory, it probably wasn't any of those things. One of the real secrets of white-hot attraction is something a lot less sexy, according to a recent study published in Nature: It's a part of your genetic coding.

All humans have their unique human leukocyte antigen (HLA) complex, which helps the immune system differentiate between their cells and those of unwanted viruses and bacteria. However, they can also be hugely influential when it comes to attraction. The researchers studied attraction patterns in 254 couples and found that having two very different HLA complexes "correlates with sexuality and enhances the desire to procreate." That means your genes determine how strongly you desire a romantic relationship. So opposites do attract!

It may also account for why you think your significant other smells so good. The researchers observed that most couples were more inclined to think fondly of their partners' odors if their HLAS differentiated. (However, the researchers noted that because predilections for odor were self-reported, it could have been influenced by the fact that they were already smitten and in a relationship.)

 All of this is more than just quirky trivia to shout out at a bar. It can benefit evolution, at least in the case of animals. The researchers found that if two animals with unalike major histocompatibility complexes (MHC), which is what scientists call all animals' version of HLA, loved each other very much. They mixed their bodily fluids, then their baby would be born with a super-charged immune system.

Instead of asking "hey, baby, what's your sign?" next time you're out, try asking "what's your genetic HLA blueprint?"