First, as with anything, one needs to look at the actual studies. As I mentioned, I don’t have the studies Sweet is citing. What I try to look at is the quality and breadth of a study. We are talking about large averages for crude categories when we talk about a “race based gap.” So I would not be the least surprised to find superior performance from an immigrant group against some other baseline group in a narrower study. Surely the best and brightest of a given source population are the ones who are most likely to get the emigration ticket out of the host population. On the other hand, SAT data that I (and Sweet reference) is an “all-comer” kind of study for populations being looked at.
I listed the citations around poverty, cultural bias and schooling for you because they are common putative reasons brought up (you may have invoked them yourself on occasion) for non-genetic reasons for the black-white gap. It’s nice to see them acknowledge in your own cite, so I hope you don’t invoke them again.
I am really curious about this statement: “Millions of ethnically Black Americans lack sub-Saharan genetic markers. They do. The gap follows self-identity, not genes.” What is the source of it? And is Sweet saying that "millions of ethnically black americans don’t derive a significant part of their ancestry from sub-saharan africa? If so, where does he think they derive their ancestry from? Are there millions of Navin Johnsons out there, or was this data simply culled from DNA testing that happened not to have a very broad cross-section of sub-saharan genetic lines? Were all those millions actually Swedes or something?
Finally, the idea that many whites have some recent sub-saharan ancestry and many US blacks have some recent european ancestry is well accepted. We would expect that such genetic admixing yields intermediate results for the averages on (for example) psychometric testing for those groups, and as it turns out, it does. Jensen and others use this as support of their genetic hypothesis. I don’t think anyone contests the idea that there is some sub-saharan-european genetic admixture in much of the US population; generally more european ancestral genes in the black population than sub-saharan in the white population (black and white being defined by self-identification).
If, by “no genetic evidence” you mean no identification of the exact gene variants involved in differences, you are right. This is not the same as saying there is “no evidence,” since it is a reasonable assumption that confounding variables can be studied and normalized.
I suspect the black-white (and the asian-white) gap will be with us for the forseeable future, efforts to eliminate notwithstanding.
In the interim, I remain concerned that if we insist such a genetic explanation does not exist, we will lose social policies such as race-based AA that help ameliorate the effects of a genetic difference.