Case #6: Malaria in the Tropical Americas Today, malaria appears throughout the tropical Americas. However, Native American populations only have “normal” hemoglobin (they are 100% homozygous for normal alleles and do not have any hemoglobin variations that protect them from malaria, as is seen in human populations in Africa, Asia and Europe). Why do Native Americans not exhibit any genetic diseases that make them better able to survive malaria?