The possible history of it is indicated on the page, I just couldn’t fit it in the excerpt.
Chromosome 9, which carries our main blood type genes, has A and B — which differ by I think seven base pairs — and O, which is identical with A but is missing the leading base pair, making it non-functional, also carries the MN blood group, which is pretty small in terms of the world’s population, but somewhat common around the Bay of Bengal, if memory serves.
My dad was AB neg.
I’m B neg...