Nicholas Wade's new book A Troublesome Inheritance: Genes, Race and Human History is barely off the presses and it has already been the subject of numerous reviews, largely because of its provocative argument for the reality of human races, based on recent studies that associate different statistical genetic clusters with particular continental groups. I have yet to read the book, but one author of such reviews in particular caught my eye: Agustin Fuentes (see here and here), in part because of his assertion that:
If you are making a scientific argument about genetic variation, you need to focus on populations -- and be clear about your definitions. Throughout the book, Wade uses the words "cluster," "population," "group," "race," "subrace" and "ethnicity" in a range of ways, with few concrete definitions, and occasionally interchangeably.
I focused on the connection between the concepts of race and population – and time – in a recent talk; for those who want the gory details, it's at minute 43 of this video. (I recommend the other talks as well!)
Fuentes quotes Wade as saying, "People as they spread out across the globe at the same time fragmented into small tribal groups. The mixing of genes between these little populations was probably very limited." But many biologists have offered quite different pictures of human interactions; see, e.g., the "trellis model" of Alan Templeton, who has provided good reason to think that "African and Eurasian populations were linked by recurrent gene flow, certainly over the last half a million years, and probably longer."
But if Templeton's picture of human evolution is correct and Wade's is incorrect, then those clusters are the products of survival and reproductive interactions between individuals from many different populations during many points in time. There is no reason to single out some particular point in time when one's ancestors lived on a particular continent and interbred with particular individuals (themselves having origins in multiple populations), producing the genetic sequences that one now has, since there are many such time periods and many such populations. To pick out continental groups (I hesitate to say "populations," because they probably weren't and probably aren't) as special in some way, and to label them "races," is entirely arbitrary. (For a great discussion of this point, see Lisa Gannett's 2005, pp. 1237-8).