Tuesday, May 30, 2006
So much for outward appearances. 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 plays a critical role in the ability to fight pathogens. Mates with dissimilar MHC genes produce healthier offspring with broad immune systems. And the evidence shows that we are inclined to choose people who suit us in this way: couples tend to be less similar in their MHC than if they had been paired randomly.
How do people who differ in their MHC find each other? This 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 -- except that there is an alarming exception. For women taking hormone contraceptives, the reverse is true: they prefer men whose MHC genes are similar to their own. Thus, women on the pill risk choosing a mate who is not genetically suitable (best to smell him first and go on the pill afterwards). This is a prime example of how chemical attraction can depend on your circumstances.
This last finding raises several interesting questions: Do women find thier existing partners less attractive when the go on/off the pill? Does this make them more likely to break-up/divorce during these periods? How are the children of women who met their partners while taking the pill different from other children? Does any of this create a natural experiment we can use to identify some interesting causal relationship.
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