An allele that causes an altered form of hemoglobin occurs in all human populations as a result of mutation. However in populations where malaria is a threat there is a relatively higher percentage of individuals with the allele. Individuals who have one allele for this condition have an increased resistance to malaria. Individuals with two alleles for this condition have significant medical problems and die young. This allele has been found in high numbers in certain populations in West Africa, Southeast Asia and Greece. 1) What process of evolution likely led to the appearance of this allele