Ta-Nehisi has used an imagine of Walter White, the first African American head of the NAACP, to illustrate the pliability of the black identity. It certainly shows that there are no fixed definitions of race which are particularly useful. But that is a misconception of biological science, which is rife with exceptions and boundary conditions, and characterized by an instrumental perspective. The data above suggests that self-identified African Americans are characterized by some African ancestry, but over 90% are more than 50% African in ancestry. Walter White, who had five black great great great grandparents and 27 white ones, was almost certainly less than 20% African in ancestry. There are such people even today, but they are not typical, and do not disprove the reality that African Americans are predominantly of African ancestry.
As expected, PCA on our entire sample revealed the greatest genetic differentiation between the US Caucasians and the Africans, with the African Americans intermediate between them, reflecting their recent admixture between ancestors from Europe and Africa. Our estimate of European individual admixture (IA) in the African Americans was also roughly consistent with prior studies , with an average of 21.9%. We found considerable variation among individuals in terms of European IA, and a number of individuals with particularly high European IA values (eight individuals of 136, or 6% with values greater than 45%).Prior studies focusing on mtDNA and Y chromosomes have found a greater African and lesser European representation of mtDNA haplotypes compared with Y chromosome haplotypes in African Americans, suggesting a greater contribution of African matrilineal descent compared with patrilineal descent [6,7]. For example, Kayser and colleagues  estimated that 27.5% to 33.6% of Y chromosomes in African Americans are of European origin, compared with 9.0% to 15.4% of mtDNA haplotypes.
"Race" as a term is very nebulous. But human subgroups with similar ancestries can have group differences in DNA -- and intelligence is highly unlikely to have no genetic basis at all (although most now believe its impact is greatly qualified by cultural and developmental differences).
But what I really want TNC to address is the data. Yes, "race" is a social construct when we define it as "white", "black," "Asian" or, even more ludicrously, "Hispanic." But why then does the overwhelming data show IQ as varying in statistically significant amounts between these completely arbitrary racially constructed populations? Is the testing rigged? If the categories are arbitrary, then the IQs should be randomly distributed. But they aren't, even controlling for education, income, etc.