post_chemistrySexual chemistry. How to find it, how to keep it alive: these are topics I’m asked about dozens of times a month, both by singles still seeking soul mates and long-marrieds hoping to turn dying embers of desire into a renewed flame. Chemistry presents a puzzle because, although we all recognize it when we feel it, most folks couldn’t offer a recipe for chemistry to save their lives. We know that it has something to do with a person’s visual appeal, and something to do with their personality and style, and something even more to do with amorphous “stuff” that can challenge common sense and sanity.

Most of us are consistently attracted to a certain physical “type,” but even someone who fits that ideal to a T can utterly fail the chemistry test. What’s missing? Well, if you conjure up an image of that ex-lover who can still give you butterflies – even though he or she was never really your type at all – you know the power of that elusive “x-factor.” The real trouble with chemistry is that it doesn’t listen to reason, and it certainly doesn’t listen to you – it just is!

So, is that the end of the story? Are you doomed to date into perpetuity and wait for a tidal wave to knock you over when you least expect it? (Probably.) Is there no better way to narrow the field? (Keep reading.) And what about creating a chemical blaze when it’s not present to begin with? Is there an accelerant that will do the job? Fascinating research suggests that there may be a few new ways to understand chemistry’s mysteries. So, let’s take a peek and see if science can help you mix up the right potion for lusty loving, too.

The Science of Sexual Chemistry

Popular buzzwords among sexual scientists these days include the likes of “evolution,” “natural selection” and “sexual selection.” By explaining chemistry on the basis of how nature has designed humans to perpetuate the species, evolutionary theories allow us to step back from our own seemingly unique and muddled attractions in order to obtain a historical view of our predicament. However, the question of whether evolutionary psychology has all the answers is hotly debated among academic types – and, personally, I’m skeptical. Even so, the research inspired by these theories sheds some fascinating light on the birds and the bees.

Doe-eyed Women and Hulky Men

If men as a group have a “type” in purely biological terms, they lean toward women who can reproduce healthy offspring to carry their genetic traits into the future. If women have a universal “type,” it’s men with great genes who are able to protect and care for the family. If this sounds very 1950’s, it’s because evolutionary theories insist that despite persistent cultural changes, the human species continues to live by the same prime directive: go forth and multiply. Mating, then, is a search for the best genes, and the chemical sizzle we feel with certain prospects is based on recognition of their compatible biological traits. Since DNA scorecards aren’t yet part of our dating personals profiles, we aim to discern whose genes are worthy by following our attractions.

Men desire women whose faces suggest youth and fertility: such signifiers include full lips, doe eyes, and a low waist-to-hip ratio. Women react lustily to men with masculine features – broad shoulders, muscularity, strong jaw and heavy brow ridge – because this is how good, testosterone-laden genes are visually displayed. But not everybody can attract “ideal” mates. So, in point of fact, people most often pair up with others who are similar to themselves in attractiveness, intelligence and status.

The Family Dynamic

Since people can respond only to the pool of potential partners who are immediately available to them, most are either repelled or stirred by countenances that are familiar. If all the women you grew up with are cute leggy blondes and your relationships with them were highly charged, it will be no surprise to anyone when your Geiger counter goes crazy over that cute leggy blonde dating your best friend. What’s more, nobody but your best bud will be shocked when you move heaven, earth and friendship to get closer to her. Furthermore, since first loves often foreshadow later loves, the type who gets your blood boiling may turn out to have characteristics or features more like your “unavailable dad” or “crisis-junky mom” than you’d care to admit.

The Immunity Detector

In terms of pure chemistry, here comes the big guns: you’ve probably heard of the “sweaty T-shirt study” where women were asked to sniff the underarms of clothing worn by various men, then rate their scent-appeal. And then there was the sweaty swab study, where eau de armpit was swiped and whiffed. If these sound like gross experiments, it helps to understand their purpose: the researchers were looking for reactions to olfactory evidence of a particular set of genes, known as the “major histocompatibility complex” (MHC), which plays a critical role in the ability to fight disease. The t-shirt study found that people tend to rate as most attractive the scents of those with MHC dissimilar to their own. The evolutionary explanation: mates with dissimilar MHC genes produce babies that are more resistant to a greater number of diseases.

MHC attraction is currently thought to be one of the keys to unraveling the puzzling nature of “chemistry,” since part of that X-factor is the desire to snuggle into someone’s scent, to breathe deeply of their skin, their hair, their sexy juices – and to find them irresistible. The one whose aroma you can and do resist is the one that evolution (not karma) says you weren’t meant to be with. Romantic destiny and soul-mate detection may be at least one part olfactory preference ordained by evolutionary biology. But there is one rather disturbing exception to this rule: Women taking birth control pills are just the opposite. They are attracted to scents just like their own. This should make us wonder what happens when a woman popping the pill meets a man, falls in love, hooks-up for good – and then she stops taking the pill! Does her attraction to her spouse wane? Further research is clearly needed to address this question.

More research is necessary along another track, too: since mating research focuses largely on college-age heterosexuals, the studies raise obvious questions about their usefulness when applied to GLBT folks, or even to older partners who have long passed the baby-making stage. Of course, we could extrapolate from this research to persons of all ages, genders and romantic persuasions, and theorize that if your sniffer is online, you will seek and seduce the right MHC match regardless of age or sexual orientation. While there’s logic to this hypothetical extension of the studies, it has yet to be borne out by research.

Sex = Oxytocin = Love

During sex and orgasm, the brain releases the substance oxytocin, known as the bonding chemical. From an evolutionary point of view, oxytocin facilitates child rearing in animals and humans. The more frequently we have sex with someone, the more oxytocin we release, and with that comes the warm fuzzy appreciation of chemistry and connection that we call “love.” The upshot of this biology lesson is that “casual sex” is never assuredly casual for any two people who have sex more than once. Your 30 year-old intellect may call your weekly hook-up “casual,” but your millions of years-old biochemistry will prod you to call it “making a family.”

For women, the stakes are especially high during ovulation, when females are attracted to highly masculine appearing men. That means that the urge to merge during a woman’s most fertile time is incited by men who are more testosterone-heavy. Add the oxytocin effect to this brew, and a careless fling can precipitate a wild ride with someone who could be decidedly wrong for the long haul.

What It All Means

Obviously, chemistry is part of who we are, part of our humanness, and certainly part of our sexuality. To ignore that fact is as foolish as it is to allow chemistry to hold our common sense hostage. Everything I’ve seen in my career as a relationship/sexuality therapist, and everything that research has thus far determined, leads me to believe that we should take the power of chemistry quite seriously. We should make sure we like the way our partners affect ALL our senses, and we shouldn’t try to overlook lack of chemistry in the interests of pursuing a “wise” relationship choice. That tactic is likely to backfire later if not sooner. However, because chemistry exists to initially drive us toward a mate – but it is not necessarily designed by nature to sustain itself indefinitely – the presence of chemistry is no guarantee of lasting passion. Keeping a chemical fire burning brightly as the years pass requires a couple’s deep devotion to tending the flame.

In the dating world, it’s worth heeding some of the lessons of evolutionary science before signing on the dotted line. For example, if you’re a woman who gets smitten by a new man during the fertile phase of your monthly cycle, take a step back before you trust that magical zing, and, for goodness sake, don’t rush into the sack! In fact, it’s probably smart to give yourself a whole menstrual cycle to see how you react to any new relationship candidate before concluding that the chemical connection is either going to thrive or dive.

And, if you’re on oral contraceptives, consider taking a break from the pill and using a different form of birth control before committing to any mate. Seriously!

While there’s much about sexual chemistry that is both bizarre and mysterious – and we know it can ensnare us as easily as inspire us – studies of long-term relationships do give thumbs up to chemistry, too. Research tells us that “mutual attraction” ranks among the top 5 traits that predict successful committed relationships. So, go ahead and follow your passions – just be sure to check in with your good sense along the way.