Ah, okay. I thought you were offering your own theories, rather than quoting from a web-answers site.

I checked out the link, and the answers are mostly worth less than the paper they're not printed on, IMHO. In addition to the linguistic confusion, I very much doubt you could find many biologists/geneticists today who would agree that "there are [exactly] three races". Some scientists prefer not to use the term "race" at all; others may think the term is still valid in certain contexts, but they would insist that racial categories -- and thus the total number of races in the human species -- are totally arbitrary.

So you could, if you wished, divide humans into three races, or six races, or twelve, or whatever. As far as our genes are concerned, you could assign people to races based on the A,B,O blood-type system, or based on lactose-tolerance, or whatever. It's a matter of academic convenience, at best -- and any claim that there are "exactly three," with everyone else being mixtures of these, is scientifically meaningless.