”I have noticed,” says my handsome 55-year-old date, settling back in his chair, his deep-brown eyes misting slightly, “that certain women in my life have asked to keep particular items of my clothing. Like my Calvin Klein underpants. Apparently, it makes them feel good.” He smiles. “One woman rings me up, years after our relationship, and says, ‘I want to let you know… I’m naked and I’m wearing your shirt.’”

My mind floods with images of jilted exes slouching on sofas in nothing but my date’s oversized boxers. It seems strange to me that anyone should find his old clothes erotic. But to Dr Tamara Brown, a Croatian geneticist based in Zurich, this makes total sense. For five years she has been investigating what creates that initial “spark” between two people, and she believes that the answer lies in smell — secret signals we pick up subconsciously. These scents lurk in our body odour, created by the genes involved in our immune system. More specifically, a section of DNA called the human leukocyte antigen, or HLA.

The catalyst for her journey was the “T-shirt experiment”, a Swiss study at the University of Bern carried out in the mid-1990s that screened the DNA of male and female volunteers, then asked the women to smell T-shirts that the men had worn for two consecutive nights and rate them for “attractiveness”. The women, it turned out, preferred the smell of men with genes that were different from their own in this HLA section. All the women, that is, except for those on the contraceptive pill, which seems to affect their sense of smell. The study provoked headlines suggesting that women who came off the contraceptive pill might also go off their mates.

Dr Brown, an elfin 32-year-old, has thought a great deal about what she calls the “chemistry of attraction”. “Somebody might not be Brad Pitt-good-looking,” she says, “but there’s just something about them and you can’t put your finger on it. Matchmakers and online dating sites often have people coming back after a first date saying, ‘We had a great time, he’s a great guy, but there’s no spark.’ So I figured that there’s a need to let people know the chemistry before they meet.”

In 2003, Brown started researching her own formula for attraction by looking at these HLA genes. “Everybody knows there is ‘chemistry’ between people — but at the time I didn’t know if we’d find out something worthwhile or economically viable as a business concept.”

Her research at the Swiss Institute for Behavioural Genetics, from 2003 to 2007, convinced her she was on to something. She believes she has found the attraction formula — based on patterns in the HLA genes — and turned it into a computer program, an algorithm that she is keeping to herself.

Since it launched last autumn, her Zurich-based company, GenePartner, which charges clients $99 for a genetic match, has been covered by, among others, ABC’s Good Morning America, the Discovery Channel and New Scientist.

I check out her website. A smiling, blue-eyed couple frolic on a sparkling white beach next to the words “GenePartner. Love is no coincidence! Matching people by analyzing their DNA”. If couples are a good “biological match”, says the site, there is more chance of “forming an enduring and successful relationship; having a satisfying sex life; higher fertility rates and healthier children”.

All this from DNA samples?

“We don’t claim to provide the ideal partner based purely on DNA,” Brown says. She adds that people also need to match on a social level — to have similar life goals, ideals and education levels. To make these matches, she has teamed up with more conventional online dating sites.

According to the instructions, all I have to do to find my ideal match is to take a cheek swab, which picks up cells from my cheek lining and acts as a sample of my DNA, and send it off to Zurich. But I must have people to match myself to. Brown offers to test five men (ones that I already know a bit about, to cover the “social compatibility” requirement), so for a few days I am casting a critical eye over potential mates in my building. As it turns out, getting men to give up their DNA is easy. “It’s just a cheek swab,” I say. Only one refuses.

GenePartner is not the first company to use DNA testing as an extension to the online dating market. The Florida company ScientificMatch started in December last year, about the same time as GenePartner, offering DNA matching for a lifetime membership fee of $1,995.

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