Major Histocompatibility Complex Alleles, Sexual Responsivity, and Unfaithfulness in Romantic Couples

TLDR

MHC dissimilarity preferences have been observed across species and are thought to promote genetic compatibility, reduce inbreeding, and enhance offspring immunocompetence, potentially influencing human sexual attraction. The study examined whether MHC similarity between romantically involved couples predicts aspects of their sexual relationship. Researchers typed alleles at three MHC loci in 48 couples, all women of whom ovulated normally. Higher MHC similarity was associated with lower female sexual responsivity, more extrapair partners, and greater attraction to other men, especially during the fertile phase.

Abstract

Preferences for mates that possess genes dissimilar to one's own at the major histocompatibility complex (MHC), a polymorphic group of loci associated with the immune system, have been found in mice, birds, fish, and humans. These preferences may help individuals choose genetically compatible mates and may adaptively function to prevent inbreeding or to increase heterozygosity and thereby immunocompetence of offspring. MHC-dissimilar mate preferences may influence the psychology of sexual attraction. We investigated whether MHC similarity among romantically involved couples (N= 48) predicted aspects of their sexual relationship. All women in our sample normally ovulated, and alleles at three MHC loci were typed for each person. As the proportion of MHC alleles couples shared increased, women's sexual responsivity to their partners decreased, their number of extrapair sexual partners increased, and their attraction to men other than their primary partners increased, particularly during the fertile phase of their cycles.