Even though I dont agree with you I will commend you for focusing on the key issue instead of chasing down side-alleys. But in fact your analysis, while commonly held, is fundamentally incorrect. These are not biological divisions but simple *statistical differences* - and much, much smaller than the differences between individuals of the same 'race.' You can redraw your *race* lines in a hundred different pseudo-random ways and get several hundred different groups that will all be somewhat mushily distinguishable on the basis of tiny statistical differences but that doesnt mean there is any real biological division there. The difference between two individuals is typically orders of magnitude larger than the differences between these supposed races.
Which indicates clearly they dont really exist. They are socially constructed categories given added and undeserved credibility by the assumption that they reflect a biological reality to which, in fact, they bear little to no resemblance.