Of late people have been leaving off-topic comments early on in threads. I don’t understand why this is happening, as I always post (or try to) an “Open Thread” every Sunday. I don’t post enough at this point where this isn’t usually on the front page, or near it. Please make use of it! From now on I’m going to just not publish off-topic comments because it seems a little rude that people don’t post them in “Open Thread”. I see the beginning of all comments as I have to approve them manually right now, so there’s no reason to hijack another thread. It just annoys me, and probably makes me less likely to actually respond.
A lot of these off-topic comments lately have been about Nick Wade’s new book, A Troublesome Inheritance: Genes, Race and Human History. The reason I haven’t reviewed it is that I haven’t read it, and the reason I haven’t read it is that I don’t have the time. It is easy for me to read an article or paper, and then put up a quick response. Or perhaps one of my own analyses of data sets I have lying around. To read a book and then review it takes a lot more time. Second, there have already been a lot of reactions on the book, so I don’t see what I would have to add. Nick actually told me around four years ago that he was thinking about writing this book, so its appearance did not surprise me at all, though the mainstream reaction seems more muted than I would have guessed.
Some general points though. First, the modern American consensus that race is a social construct is true but trivial. It’s true because a de facto race such as “Latinos/Hispanics” were created in the 1960s by the American government and elite for purposes of implementing public policies such as affirmative action. Obviously this is a classic case of a social construct, as the quasi-racial category is based upon social, not biological, factors (Latinos/Hispanic can explicitly be of any race, though implicitly it’s transformed into a non-white class in the United States). A group like “black Americans” ranges from people with considerably less than 50% African ancestry to more than 90% African ancestry (though almost always black Americans who are not immigrants from Africa or first generation offspring of those immigrants have some segments of European ancestry). The problem is that people move from this non-controversial point, that some racial categories are social constructs, to the assertion that all racial categories are social constructs, and that phylogenetic clustering of human populations is irrelevant or impossible. It is not irrelevant, or impossible. Human populations vary, and that variation matters. Human populations have specific historical backgrounds, and phylogenetics can capture that history through methods of inference.
Moving from phylogenetics to population genetics, there is the question about whether population-genetic dynamics such as migration, drift, mutation, and selection have resulted in significant variation across human populations. Yes, they have. Human populations have significant functional differences which track regional adaptation, and also correlate to an extent with racial clusters, and phylogenetic history. The details here are empirical, and you need to take into account what we’re learning about human demographic history to make sense of how and when adaptation occurred. This where the controversial aspects of Wade’s book come in, because he argues that there are behavioral differences across populations due to distinctive evolutionary histories. Complex traits like behavior are often subject to numerous upstream causal variations, so untying the knot is not easy.
But I don’t think it’s impossible, and I suspect there are indeed behavioral differences between populations due to genetic differences between populations. The problem is that we haven’t really done enough research in this area to talk about the genetics of it in anything more than a speculative fashion, and complex traits which are less controversial and more tractable than behavior or cognition, such as height, have already presented difficulties for researchers despite extensive devotion of resources. But the truth of the matter in this area will come out at some point. As it is right now, it does indeed seem that the small differences in height between Northern and Southern Europeans are due at least in part to differences in frequencies of alleles which are known to influence height.