🤫☠️ Friends tend to be more genetically similar to one another than they are to strangers. The study found that friends shared more genetic variants than would be expected by chance. On average, the degree of similarity was comparable to that between fourth cousins. The pattern persisted after researchers accounted for race and shared ancestry. It extended even to genes involved in smell, food metabolism and immune function. Across the genome, friends tended to share more single-nucleotide polymorphisms (SNPs) than strangers did, a pattern known as genetic homophily. This suggests that friendship may act as a form of “functional kinship”. In some groups of genes, however, friends were more likely to differ, a pattern called heterophily. Three groups of genes stood out: ▶️Sense of smell: similarity. Friends tended to share variants in genes that help translate odours into sensory signals. In other words, people who “smell” the world in similar ways may be more likely to become friends. ▶️Linoleic acid metabolism: similarity. Friends also showed similarities in genes involved in processing this dietary fat. One possible advantage is that friends may have similar food preferences or metabolise what they eat in similar ways. ▶️Immune system: difference. Friends tended to differ in genes involved in immune responses. Those differences could be complementary if they help each person resist different pathogens. The variants for which friends showed the greatest similarity also showed stronger evidence of recent positive natural selection. The authors interpreted this as a sign that choosing similar friends may have offered an evolutionary advantage. Earlier studies had linked friendship to observable traits, both physical and psychological. These findings suggest that friendships may also reflect subtler genetic patterns that people cannot directly perceive. Similarities may be beneficial in some traits and differences in others. The study raises the possibility that both patterns played a role in recent human evolution. #info #meta #nationalism
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