[1] Reproductive compensation refers to the tendency of parents, seeking a given family size, to replace offspring that are lost to genetic disorders.
It is a theory that suggests that behavioral as well as physiological factors may play a role in the level of recessive genetic disorders in a population.
As a consequence, parents with otherwise reduced fertility have a greater influence on the frequency of recessive alleles in future generations.
[5][6] Whereas heterozygote advantage can explain the persistence of high carrier rates of lethal alleles in certain regions (e.g. sickle-cell disease in Central and West Africa), Johan Koeslag and Stephen Schach [7][8] have suggested that reproductive compensation might explain why different communities have high carrier rates for differing lethal alleles, despite living in similar or sometimes the same environment.
Examples are Tay–Sachs disease amongst Ashkenazi Jews, cystic fibrosis amongst people of West European origin, and phenylketonuria among persons from Ireland.