Why is only 1% of the populations blood type AB- (AB Rh Neg)?
The reason only 1% of the population’s blood type is AB- is because of the founder effect. Small populations were founded geographically by people with O+ blood. These populations grew into larger groups with disproportionate frequencies of O and +. This is why O+ is the most common blood type, even though O is the recessive. The reason for the different types is simple- since none of them is particularly selection stopping, there’s no reason for them to breed out. Humans vary, that’s the way of it. By the way, in some subgroups of humans the founder effect had the opposite effect. There are indigenous American populations that have virtually no O in them, resulting in the highest concentrations of AB blood in the world.
