Now, for the cold, hard facts ~ hemaglobin is a product of the action of several different genes. First you need to have heme produced. It comes in two forms ~ left handed and right handed. Not all human beings make both forms ~ there are mutant varieties that make only one type! The original humans excrete the type of heme they don't need to keep around for the production of hemaglobin.
Currently there are only a few hundred of these "original" types around ~ in Scandinavia. There are several thousand of their relatives in the United States. Many of them experience some degree of indeterminate infertility when they attempt to breed with other species of humans.
Compounding the picture there turn out to be 82 different alleles of the critical gene for manufacturing heme, and some of the other variations are so incompatible with each other than fertile offspring are not possible or are exceedingly rare.
Again, this is just one gene with 82 different forms ~ and you can end up with what amounts to speciation.
Do you have any cites for what you assert here? I would like to know more details.
ML/NJ