As long ago as the 1950s, a perfumer called Paul Jellinek noted that several ingredients of incense resembled scents of the human body. It was not until 2001, however, that Manfred Milinski and Claus Wedekind of the University of Bern wondered whether there was a correlation between the perfume a woman preferred and her own natural scent. They found that there is.

The correlation is with the genes of what is known as the major histocompatibility complex (MHC). This region of the genome encodes part of the immune system. It turns out that one of the most important aspects of mate choice in mammals, humans included, is to make sure that your mate’s MHC is different from your own. Mixing up MHCs makes the immune system more effective. The MHC is also thought to act as a proxy for general outbreeding, with all the hybrid vigour that can bring. Fortunately, then, evolution has equipped mammals with the ability to detect by smell chemicals whose concentrations vary with differences in the MHC of the producer.

That means people are able to sniff out suitable MHC genomes in prospective partners. A woman, for instance, will prefer the smell of T-shirts that have been worn by men whose MHC genes are appropriately different from their own. Dr Milinski and Dr Wedekind also found an association between a woman’s MHC genes and some of her preferences for perfume. Perception of musk, rose and cardamom is correlated with the MHC. Perception of castoreum and cedar is not.

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