Sniffing someone's armpits does not sound the most promising start to a date. Research, however, suggests that it will probably turn up a better prospect than either a blind date or gabbling nervously to 20 consecutive strangers. Now a new dating website, ScientificMatch.com, promises a discreet way of letting you nose out potential partners.

Researchers found more than a decade ago - by asking female students to sniff T-shirts worn by men - that ovulating women rate certain male body odours as sexier than others. Crucially, the preferences depended on a certain part of the immune system called the major histocompatibility complex (MHC). Women, it turned out, were bewitched by the odours of men whose MHC genes were most different from their own, and repelled by the aroma of men with similar MHC genes.

This led to the idea that certain aspects of body odour evolved as a signal to potential breeding partners. Bagging a mate with a different range of “immune” genes from you makes sense on two levels: your children will inherit a more diverse range of immunity genes, and thus fall prey to fewer diseases; it also guards against inbreeding, since kinfolk have similar MHC profiles.

ScientificMatch.com, started in Boston two months ago, is convinced that love is governed by such chemistry, but the science of passion doesn't come cheap. For around $2,000, you send it a DNA sample and a profile of your interests. You are then provided with scratch-and-sniff patches of three immunologically matched soulmates (who hopefully also share your penchant for arthouse movies, pub quizzes and pizza).

Why bother? Fit children are one obvious benefit; this biocompatibility could also leads to higher rates of orgasm and fidelity. Plus, if he's going to leave his dirty T-shirts on the bedroom floor, they might as well smell nice.

Men think about sex even when crossing the road. Professor Robin Dunbar, from Oxford University, observed 1,000 pedestrians at a crossroads in Liverpool. Men made more dangerous crossings when women were looking, which suggests risk-taking is a mating display. Women, though, were far too sensible to risk life and limb to impress a male bystander, according to Science.

Having an ageing population could provide an unexpected bonus: world peace. Mark Haas, a political scientist at Duquesne University, Pennysylvania, argues that troublespots such as Pakistan and Iraq have demographic “youth bulges” that will be ironed out by 2030, thanks to falling birthrates and rising life expectancies. And greying countries will spend more on looking after the elderly and less on warmongering, leading to a “geriatric peace”.

The position of America as the world's superpower will face fewer challenges, particularly from an ageing China. So, peace - but on Uncle Sam's terms.

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