Redhead Genes Show Immune Perks, But Higher Autoimmune Risks

A Harvard Medical School study of ancient DNA from about 16,000 people over 10,000 years finds that the genetic variants behind red hair and fair skin may confer immune benefits (including potential HIV resistance and leprosy resistance) and lower arthritis risk, but also raise the risk of Crohn's disease and celiac disease due to gluten sensitivity, suggesting a trade‑off shaped by ancient selection and the spread of wheat farming.