No-one knows exactly what causes it, but attraction is the one factor that is make or break in any relationship. It completely overrides your mental check-list for your ideal mate (religion, education…), and it’s certainly not something that can be learned with time.

My Chemical Romance

Pheromones are chemicals you emit without even knowing – they’re like odourless scents that trigger sexual responses in others. They are probably responsible for attracting the biologically perfect partner for you – signalled by that feeling of sexual attraction. It’s quite literally chemistry!

The sexual area of the brain reacts to these chemicals in quite different ways to ordinary scents. For example, for men, women’s pheromones activate the hypothalamus (the region of the brain that controls sexual behaviour and the hormones), but has no effect on women. Meanwhile, for women, the male chemical stimulates the hypothalamus. And interestingly enough, gay men respond sexually to male pheromones in the same way as women do.

Animal Attraction

Pheromones affect us at a totally unconscious level – in fact, they take us right back to our animal instincts. In the animal kingdom, for example, male mice produce chemicals that attract females and anger other males. Old elephants at the head of the herd prove their sexual prowess by exuding a powerful mix of chemicals that younger bulls are not able to produce yet.

And as animals can sense when their mates are most fertile, so can we – we just don’t realise it. During certain times during a woman’s menstrual cycle when she is most fertile, her pheromones send out a more attractive scent.

Meanwhile, women are most attracted to more masculine-looking men at the most fertile time of their menstrual cycle (and can even sniff out their scents), but choose men with more feminine-looking faces the rest of the time.

It could be because kinder-looking men are seen as better for a long-term partner, while masculine men appear stronger and healthier – better equipped for producing children.

Being on the contraceptive pill sends things out of whack though – possibly causing a woman to stop producing pheromones and reducing her ability to pick up male scent signals.

Another strange fact? Our perception of how attractive a person is, is altered by the chemical signals they give out. And believe it or not, less attractive women send out more seductive scents – it could be evolution’s way of giving plain women a fair chance, and stopping very attractive women being pestered!

All in the Genes

Finding all this a little too unromantic? Well it gets worse. It turns out that genes are the main reason certain peoples’ pheromones drive us wild. According to research, we’re attracted to people whose DNA fits in nicely with ours – so even if you’re not planning on having kids anytime soon, you’re being helplessly drawn to the perfect breeding partner every time you scope out a party for a one night stand!

Oh, and if you thought your last relationship ended because your partner just couldn’t stop leaving their clothes all over the floor, you could be wrong. Research shows that a massive 35 per cent of the reason for a relationship working or not is genetic, pure and simple. In fact, it’s scientifically proven that if your spouse has genes that complement yours, you’ll have a happier marriage.

Blame it on evolution, but the fact is that some genes work better in combination together than others. You’re naturally more likely to be willing to compromise with and make sacrifices for someone who is similar to you genetically, but at the same time not too similar to prevent the optimum genetics for your children!

In other words, what you think are your own lusty or romantic feelings are really your DNA’s sneaky way of making sure you continue the family line with no genetic glitches.

Genes are also to blame for the seemingly shallow factors that seem to catch the opposite sex’s attention. There’s actually a biological reason why men honestly can’t help being attracted to women with full lips, slim bodies, smooth skin and glossy hair. Men are wired to interpret these as signs of youth and health, which indicates that the woman is a prime baby-making machine.

In the same way, women just can’t stop themselves feeling attracted to men who are athletic (signals health and protection), successful (able to provide for offspring) and generous with their money (indication of future security). And naturally, they’re also attracted to men who appear to like children (Read more: A "Baby" Face Makes Women Go Ga-Ga).

True Love

It’s not all bad though. Even though we are initially attracted to people for unromantic reasons beyond our control, what happens after that is pretty much up to us.

Even science has discovered (and measured) that love is stronger than attraction. When it comes to sticking together for the long haul, having similar interests and complimentary personalities – both of which take a while to establish – mean more than that initial physical attraction.

And once love takes over, it becomes the driving force – a much more powerful emotion than attraction, sex drive, or DNA.