MHC Homozygosity Is Associated with Fast Sexual Strategies in Women

Abstract

Life History Theory proposes that individuals facing uncontrollable threats to their survival—for example, uncontrollable threats of infectious disease—will pursue a “fast” sexual strategy, characterized by earlier and more promiscuous sexual behavior. Consistent with this idea, individuals with genes that equip them with poorer defenses against infectious disease could also tend to pursue a faster sexual strategy. Within a sample of 180 women, we find that women with a genetic marker of lower immunocompetence—namely, homozygosity at the Major Histocompatibility Complex (MHC) region of the genome—report more positive attitudes towards short-term sexual relationships, a younger age at sexual debut, a more promiscuous sexual history (such as more one-time sex partners), and a greater number of lifetime sexual relationships but not romantic relationships. These findings identify the MHC as a possible source of genetic variation in women’s sexual strategies and highlight the need for further research examining the complex links between genes, immunocompetence, and social behavior in humans.