How does smell help us to choose who we marry

A. We're talking pheromones here. They are odours given off by animals and humans to affect the behaviour of others. It's generally believed that humans use them, subconsciously, to trigger sexual desire.

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Q. How do we know if they are affecting us
A. As far as we can tell, any chemical signals passing between men and women are subliminal, but we are very aware of smell generally. One American researcher asked 166 women about what makes a man attractive and all said that a man's scent was vital.

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Q. So, smell does influence who we choose as life partners...
A. Yes, it affects who we are attracted to. But modern lifestyles have turned its effectiveness around so women end up choosing the wrong men.

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It all started with an experiment run by the University of Bern, reported in the New Scientist, to find out if women used odour to choose genetically appropriate mates - i.e. one whose genes were different from their own.

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Q. How does that work
A. Studies of mice show that they will sniff out a mate with different immunity genes, and this increases their chances of healthy offspring. Having parents with very different genes may even increase your chances of being born.

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Q. What happened with the humans
A. It was discovered that women who were taking the Contraceptive Pill chose men whose immunity genes were similar to their own.

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Q. What's the Pill got to do with it
A. The Pill fools the body into believing it's pregnant, and pregnant women experience an altered sense of smell. The theory is that when she's pregnant, a woman will be most attracted to the smell of her family - the people who will naturally want to take most care of her.

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Q. So she'll choose a mate who smells like her family
A. Exactly. And choosing a man with similar genes could make it difficult to have children.

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Q. Is an unadulterated sense of smell your best matchmaker
A. Yes. Studies of a socially isolated religious community in the US, which don't use perfumes, deodorants or contraceptives, showed that only about 5% of couples had matching immunity genes.

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Q. What can women do
A. f they are on the Pill and meet a man they want to have children with, they could stop taking it and see if they still fancy him.

�By Merill Haseen