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What sources did you use to support your blood type demographics and timeline. What was your marker that identified blood types in early man (ie. DNA?) Why is AB only a recent bloodtype?
The work of physicial anthropologists Frank Livingston and William C Boyd and the paleoserologist AE Mourant. Many of their findings were the result of grave exhumations and blood grouping via reconstitution of remains. Mourant's work was centered around classic epidemiologic studies with regard to population densities. It is important to realize that the blood type genes are "squelchy": beyond the expression of antigenicity, and the production of opposing blood group antibodies, they seem to code for many secretory functions (particularly digestive), in addition to having other non-Darwinian manifestations, presumably by their interactions with co-adjacent alleles on the same chromosomes.
In understanding the presumed blood type timeline, it is important to remember that it is not probably the case for blood types to having arrived one after the other, like "Act One", "Act Two" etc: indeed the ABO mutations may have first occurred as long as 7 million years ago, but with regard to A and B there were probably only very small clusters of mutations existing in isolated pockets here and there. Eventually, with a change in conditions for the better, their special attributes became a plus rather than a hindrance. It is important to realize is that the digestive and immune characteristics of a blood group are a reflection of their response to the environmental conditions which would have served to encourage their growth and expansion. Is this an ongoing process? Undoubtably. Some sources seem to think that A is the current "wild type."
AB is recent in the sense that is is not the result of evolutionary forces. It is the result of intermingling between the A and B genepools. These two groups did not have extensive contact with each other until about AD 500 onwards.