How science guides Cupid's arrow

True love often seems beyond explanation. The black and white rules of science seem worlds away from the roller coaster of infatuation or the depression of rejection – the course of romance never runs smoothly.  But even if it can’t mend a broken heart or help you choose the perfect gift, science can help to explain some of the ups and downs of love this Valentine’s Day. Because whether you’re happily coupled up, wondering whether your partner really is your “mate for life”, or contently single – the laws of nature still apply.

Scientists have long been fascinated by the phenomenon of attraction. Beauty may be in the eye of the beholder, but there are certain features that study after study has found make a person more attractive to the opposite sex. Many of these happen to signal health, fertility and youth - traits that indicate a partner is capable of passing your genes onto the next generation.

For women, men who look masculine and have strong features are considered attractive. But preferences change with the menstrual cycle, according to a University of Bristol study. During ovulation, when a woman is most fertile, she is attracted to masculine faces that would presumably be more virile. However, the rest of the time females are attracted to men who appear nurturing, sensitive and would make a good father. Mother Nature seems to think that the best strategy for women is to have a baby with someone irresistibly masculine, but to raise the child with the sensitive best friend.

Men’s preferences are a little more straightforward: women with small waists; shapely breasts and hips; and perfect hair, skin and nails are generally the most attractive. Men, however, are also affected by a woman’s cycle. A study by the University of New Mexico has found that lap dancers who are ovulating receive better tips, suggesting that they are more attractive to men.

As well as biology, environment can also affect what is considered attractive, which is why beauty ideals change between cultures. For example, studies have found that in countries where food is in short supply, men prefer women with a high body mass index (BMI), as this indicates they are fit enough to survive and raise offspring. Although these preferences are completely subconscious, the need to pass on our genes continues to drive us towards certain people.

The science behind what we find visually pleasing, however, doesn’t explain those people we meet who are attractive, successful and charming, but whom we have no chemistry with. According to research, this is your body telling you that, genetically, this person is not right for you. A study by the University of Bern in Switzerland revealed that females are more attracted to men who have a significantly different set of immune system genes, called the major histocompatibility complex (MHC), than they do, as this pairing would give their offspring a comprehensive immune system and the best chance of survival. The amazing thing is, women can subconsciously smell whether or not a suitor has a similar MHC to her and is most attracted to the scent of a man who has significantly different genes.

This olfactory ability is lost, however, when women decide they don’t want to become pregnant. In the same study, women on the pill produced opposite results by picking men that were genetically similar to them, who would provide their children with poor immune systems. This result can be explained by the physiological modifications that occur on the contraceptive pill, but perhaps these changes also free women who don’t want children from their subconscious bias towards certain men, and allow them to select on the basis of other traits.

Of course, even after you’ve selected a partner, genetics continue to affect your love life. Scientists from the University of New Mexico found that the more varied a man’s MHC is to a woman’s, the more likely she is to be faithful to him. This could one day lead to genetic tests that predict the likelihood of a couple staying together. However with modern pressures such as stress and money, it is entirely possible that a couple can be genetically perfect for each other and still not make it work.

While love will continue to bewitch, bewilder and batter humans for generations to come, it is small comfort to think that some of the heartache is just nature giving us a helping hand with the continuation of our species. However, even with science guiding Cupid's arrow, people can still get it very wrong. Perhaps today’s high rates of divorce can be partly explained by our new methods of fooling nature. Plastic surgery, makeup and very tight underwear have all been developed to trick our mate into believing we’re more perfect for them than, perhaps, we really are. If this is the case, when it comes to matters of love it may be better to follow your nose over your heart.

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