Anthropology....????

Question

Under what conditions might deleterious mutations be selected for? (like the sickle cell trait)

Answer 1

They are not selected. They remain in the population since they can be passed on recessively (if dominant) or they do not significantly hinder procreation.

As for sickle cell, the heterozygous phenotype is advantageous in Africa because it prevents malaria.

Answer 2

Random adaptation.