The TRUTH About Evolution & “Beneficial” Mutations From Broken Cells to Biologists? Not So Fast. This is what evolutionary textbooks might not tell you about Sickle Cell Anemia—a famous so-called beneficial mutation. Sickle cell anemia is often presented as one of evolution’s “best examples” of a beneficial mutation. But look closer. It’s caused by a damaged hemoglobin protein—a broken gene that deforms red blood cells and causes serious health problems. Yes, it can provide partial resistance to