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Looking for the right mate? Just follow your nose

BY MARTIE HASELTON

We spend a huge amount of time and energy trying to select a mate, clearly the most crucial decision of our lives. Yet we’re often not satisfied. A 2005 survey of more than 900 people who had been using online dating services found that 75% had not found what they were looking for.

Some things we all find attractive. Men tend to desire women with features that suggest youth and fertility. Women have strong preferences for virile male beauty. We also know women are attracted to men who look as if they have wealth or the ability to acquire it, and that both men and women strongly value intelligence in a mate.

What about the less obvious cues of attraction? Fascinating work on genetics and mate preferences has shown that each of us will be attracted to people who possess a particular set of genes, known as the major histocompatibility complex (MHC), which play a critical role in our ability to fight pathogens. Mates with dissimilar MHC genes produce healthier offspring - which explains why couples tend to be less similar in their MHC than if they had been paired randomly.

How people who differ in their MHC find each other isn’t fully understood, but we know that smell is an important cue. People appear to literally sniff out their mates. In studies, people tend to rate the scent of T-shirts worn by others with dissimilar MHC as most attractive. This is what sexual “chemistry” is all about.

The message here is trust your instincts — but there is an alarming exception. Women taking hormonal contraceptives prefer men whose MHC genes are similar to their own, thereby choosing a mate who is not genetically suitable.

Attraction can also fluctuate over the menstrual cycle. Men evaluate women’s scents as more attractive when they are near ovulation, and in our studies at UCLA we have found that men are more loving toward their partners as ovulation approaches. Women’s preferences for certain male scents and other male features change over their cycle. Near ovulation, they prefer masculine traits; other times they prefer less sexiness and more stability.

Given these complexities, how do we settle on a particular mate? Research suggests that the optimum proportion of possible mates to examine before setting your aspirations and making your choice is a mere 9%. So at a party with 100 possible mates, it’s best to study only the first nine you randomly encounter before you choose. Examining fewer means you won’t have enough information to make a good choice; examining more makes it more likely you’ll pass the best mate by.

Whom we fall for is determined by a mix of factors, some of which we are aware of, some of which we experience indirectly. Happen­ stance can play a major role, especially if we meet someone just after calibrating our aspirations, or at a particular stage of our hormonal cycle. There may be that special someone out there — but they’re not necessarily the only one.

Haselton is assistant professor of communication and a member of the Center for Behavior, Evolution, and Culture. A longer version of this article was recently published in New Scientist magazine.