NOT only do opposites attract, they also stay together. A couple鈥檚 genetic differences seems to be the key to lasting happiness 鈥� a finding that could possibly lead to a DNA test revealing how likely a woman is to stay faithful.
Christine Garver-Apgar at the University of New Mexico, Albuquerque, and colleagues analysed genes belonging to the major histocompatibility complex (MHC), which controls the way the immune system recognises invaders. Previous research has shown that the MHC plays a role in sexual attraction, but its lasting role in relationships had not been investigated.
Garver-Apgar analysed MHC genes from 48 heterosexual couples who had been together for at least two years and asked them how faithful and responsive towards their partner they were.
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For the women, the more similar their MHC was to their partner鈥檚, the less sexually responsive they were and the more likely they were to be attracted to other men and have affairs 鈥� particularly during fertile days of their menstrual cycle. Men seemed to be unaffected by MHC similarities (Psychological Science, vol 17, p 830).
The mechanism may have evolved to produce offspring with broad immunity to disease.
