Sickle cell anemia is a genetic disorder resulting from a mutation in the HBB gene. If an individual inherits two copies of the mutated gene, one from each parent, they will develop the disorder. Populations in certain cultures in Africa and the Middle East, where marriage between close relatives is common, have a higher frequency of sickle cell anemia. This is due to the increased likelihood of both parents carrying the mutated HBB gene when they are closely related, resulting in a higher risk of their offspring inheriting two copies of the mutated gene and developing sickle cell anemia. Which type of evolutionary model best describes the case scenario mentioned?
