Some human populations may rely on biological factors in addition to social factors when selecting a mate, according to a recent study in PLoS Genetics. Scientists in China, France, and the United Kingdom report genomic data showing that immunity traits may be involved in mate choice in some human populations.
In several species it has been shown that the Major Histocompatibility Complex (MHC), a large genomic region involved in immune response, influences mating selections and that this may be mediated by preferences based on body odor. Some previous studies have reported a tendency for humans to prefer MHC-dissimilar mates, encouraging heterozygosity at MHC loci in offspring and resulting in improved immune response.
However, other studies, both directly in couples and also indirectly in "sweaty T-shirts" experiments, have reported conflicting results.