There are no Northgate computers in my lab, because Northgate went extinct even though it was, in its time, the best on the market. Major human races, in the same way, may be brands that have only been successful for a few millennia. Fifteen thousand years ago may have been a few major races, but they were almost certainly very different from what we identify as major races today. For example there are not very many Khoisan speaking small yellowish skinned people in sub-Saharan Africa but there may have been a lot of them fifteen thousand years ago. Many early fossils from this continent do not look like the contemporary inhabitants, and, interestingly, the early modern inhabitants of Europe do not look Europeans, the early moderns in Asia do not look Asian, and several of the early modern humans in Africa do not look African.
Races are transient.
It is easy to fall into essentialist thinking about race as well as about brand names. It is found in sub-Saharan Africa where there is a close association with the local intensity of Falciparum malaria. The dynamics of the spread of the gene are different from and independent of the spread of people with black skin, and this historical pattern leads to the association of the anemia and being Black in North America but not in South Africa. Similarly there is a statistical superiority of northeast Asians on IQ tests, and again we don't know the mechanism nor the evolutionary history. These statistical associations have important consequences at the population level.