We do need to keep in mind that ethnicity comes from lucky paths through the genealogical charts, and that ethnic groups with which we're familiar today weren't necessarily even around 12,000 years ago on the then-exposed continental shelves.
The gene for red hair is not now very widespread. Whether that means it is a recent mutation from a regional population which has in recent centuries been making its way through the world, or whether it means it was previously quite widespread and commonplace and through luck of the draw has vanished is difficult to prove.
Blood type is a good example of an analogous issue.
Type O is often thought to be the oldest, possibly because it is very very common among Native Americans (something like 99 per cent) which is presumed to have been an isolated population for over 10,000 years. I don't think it was an isolated population, at all, but trying to use that commonplace as an argument against contact is pretty weak for other reasons exceeding the scope, blah blah blah...
But anyway, the genes for blood type reside on chromosome 9 (this was in Matt Ridley's "Genome") and the genetic sequence that produces type A are nearly the same as type O (which produces no distinctive protein) -- type O is the same sequence as type A, with the first base pair (or maybe it was the first "word" of three base pairs; I'm too lazy to look) missing. Type A and type B are very similar, but produce different proteins. Type B is about 15 per cent of the population; type A is 40 per cent, as is type O; type AB is the result of having the A and B coding on the same chromosome and is about 5 per cent of the population.
And there's more:
Type A seems to be the original bloodtype, producing the others through mutation. The exceptions may be the MN bloodtype system, which comes from the Indian subcontinent, and are analogous (but not the same thing as) to A & B (codominant), AFAIK (it's often difficult to find anything about the MN system, which is in a very small number of people worldwide). Strange, isn't it, that a completely unrelated bloodtype system exists (still exists? recently sprang into existence?) after centuries, even millennia, of contact, intermarriage, and commerce, all over the world?More Biochemistry and "Bombay phenotype"An interesting situation arises when an individual is not able to make the "H" antigen. Such a person cannot produce the "H" antigen and even if the "A" or "B" enzymes are present, cannot make "A" or "B" antigen since there is no precursor for the antigens to act upon. An individual who cannot produce the "H" antigen will appear to have blood type "O" since this blood type is a negative category (not-A, not-B, not-A and not-B). This was first documented in Bombay and has become known as the Bombay phenotype and has been exploited on the popular soap opera General Hospital.
by Robert J. Huskey
George W. Bush will be reelected by a margin of at least ten per cent