The allele that causes an altered form of hemoglobin (Hb) occurs in all human populations as a result of mutation. In some populations, this allele has increased in frequency because it confers some resistance to malaria. Which process of evolution is likely responsible for the change?

Natural Seleccion

Explanation:

As natural selection proposes, organisms that adapt to their environment are more likely to survive and transfer the genes that aided to their survival success to the next generations.

Since this allele causes a form of hemoglobin that confers resistance to malaria, subjects that posses higher levels of this type of allele tend to survive more to a malaria than people that don't posses this form of allele, and pass on the genes to the next generations, in this case the allele, causing the Hb frequency to increase.