While Dr. Yak is largely correct on the science, and the fact that a lot of people would be surprised to find certain genetic details about themselves, Dr Yak also completely wrong.
It is completely possible to use genetic details to classify people into groups. There are certainly overlapping people, like Native-American mixed with African, and Northern European. There are lots of people signing up to find out what their "origins" are. There are definite differences between African, Asian, Polynesian, Scandinavian, Jewish, Middle-Eastern, Southern Europeans, and so on. It does not rise to the level of races within the species. Even though: Europeans are largely Homo Sapien/Neanderthal cross-bred, Southern Asiatics are largely Homo Sapien/Denisovian cross-bred, and Africans are largely Homo Sapien/Other ancient hominid cross-bred. There is some mixing of these three, making probably a whole spectrum. Again, though the homogeneity of the human species is so complete we have only one race.
Having only one race doesn't mean there are no scientifically determinate variations. It just means, you can't always tell by looking at someone, what those variations are. I think that is really what Dr. Yak is meaning. These characteristics can be used to include or exclude certain people from some exclusive club. But those doing so, would do well to test themselves first, to make sure they fit in the category they think they do.