Blood groups make no sense

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Recently I´ve been reading some rather layman literature regarding blood types, from Dr D´adamo´s much criticized "Eat right for your blood type" to the odd research papers on how different diseases affect each blood group and their supposed origins, needless to say the more I dig the more confusing it gets

Now, I´m just talking about the ABO and Rhesus types, I know theres another hundred or so ways to categorize blood groups but with just these two groups the in your face inconsistencies are staggering:

https://en.wikipedia.org/wiki/Blood_type_distribution_by_country

For instance, it´s agreed upon that blood type B originates in Asia, with some people pointing to the Himalayas and others claiming it originated in Central Asia or South East Asia, yet if you look at the chart two inconsistencies spring up:

1) If this group is Asian in origin how come it was completely absent from the Western Hemisphere until the arrival of Europeans in the XVIth century? shouldnt at least some of the people that crossed the Bering straight have had this blood type? after all it´s believed they did originate from Siberia, one of the few places on earth where type B is prevalent and, if Im not mistaken, they crossed the straigh between 50,000- 20,000 years ago when the rather new type B had already come into being.

2) This one really puzzles me. How come blood group B Rh + is overrepresented in Eastern Asia yet B Rh - is all but absent there? being relatively common in the Balkans and Eastern Europe yet more prevalent in places like the Western Hemisphere and Africa where type B in general is uncommon?

Regarding blood type O, albeit being present pretty much everywhere how come it is so common in the Americas (being pretty much the only blood type before Europeans and Africans reached the continet) AND Africa? two places that had no known contact until recently, who had it first Africans or Native Americans?

Continued.