Key takeaways:Researchers found that four immune system genes bear signatures of thousands of years of human evolution. The study identified rare variants in a particular gene that were associated with severe COVID-19 and with prior organ transplants, which are linked to greater risk of severe COVID-19. Revealing immune system genes shaped by ancient infectious diseases could eventually point to new strategies for disease prevention and treatment. Every time a virus invades a person, it collides with thousands of years of human history. A study led by researchers at the USC Dornsife College of Letters, Arts and Sciences and Howard University suggests that some of the genes involved in the body’s immune response today bear the marks of ancient battles with infectious diseases.