Americans pick mates with different immune genes while Africans prefer the genes they already have, New Scientist reports. A study of 60 couples from Utah and Nigeria showed that the Americans hitched up with partners whose genes recognized pathogens that theirs couldn't. The African marriages, however, appeared to be genetically random.
But genomes and culture may explain the differences, researchers say. The Africans, from the Yoruba ethnic group, marry distantly related mates by tradition. They also possess more genetic diversity than the Americans and may not feel evolutionary pressure to choose mates who can fight off different ailments.