Worldwide Distribution of Blood Types

How do they identify who is a 'native'? And does it not seem a bit suspicious to anybody that the area where the 'A' blood type crops up in Africa is also the same area where slaves were picked up from and returned back during abolishment?<p>Also, if you overlay the O graph on top of the B type, you see some correlation with the language family (<a href="http://upload.wikimedia.org/wikipedia/commons/b/b5/Languengl.gif" rel="nofollow">http://upload.wikimedia.org/wikipedia/commons/b/b5/Languengl...</a>) in Africa.<p>Unfortunately, the addition of european languages in South America spoils the correlation.<p>I bet it would be quite interesting to compare ethnic groups with language families and blood types.

For some reason I've always had the impression that O was rare. I cross checked with wikipedia <a href="http://en.wikipedia.org/wiki/Blood_type#ABO_and_Rh_distribution_by_country" rel="nofollow">http://en.wikipedia.org/wiki/Blood_type#ABO_and_Rh_distribut...</a> and it seems a bit less than A (O+ and O- compared to A+, A-, AB+ and AB-), but no means rare. Did anybody else have this prejudice?<p>The 'native' part also seems a little dubious. What is that supposed to mean in terms of their samples?