The Science Behind Eye Color

9. Genetics and Geography

Red hair and green eyes are often associated with Irish descent. Blue eyes and blond hair are sometimes linked as well. Blue and green eyes occur in 2 to 8% of the worldwide population. Approximately 3% of these people have blond hair, while only .05% have red hair. We regularly see these relatively rare traits, alone or together, in the United States. Although genetics of eye color, and other traits, aren't fully understood yet, geographical location and ancestry provide a basis for expectations of genetic makeup and common traits in any given population.