> However, at the level of a specific nation, during a specific period in its history: that nation may be composed of a small number of major descent groups. ... and groups A and B may also differ in their frequency of physical appearance traits genes.

That's exactly my argument. Isn't it funny that people interested in the Black IQ question just consider that the only physical appearance worth studying is the color of the skin? Cluster of people with specific genes are super common. It is why your "get my ancestor from my DNA" test is able to tell you that you are X% spanish and Y% danish. But strangely, these people are wondering if a huge group of "black skin" mixing over a full continent and a huge group of "white skin" mixing over a full continent, somehow, is the only main pertinent cluster to separate IQ.

> Because "race/ethnicity" (descent group) and "color-of-the-skin" are not the same thing.

Isn't that exactly my point?

> In certain spatiotemporally limited contexts (some countries during some periods of their history), color-of-skin can be a somewhat of a proxy for descent group, to the point that one becomes a metonym for the other, in broader contexts that breaks down.

My point is that the people interested in the Black IQ question consider that color-of-skin is the best proxy, to the point that they don't even consider that there should be other proxy.

If indeed they were just "asking a scientific question", why are they always asking "what about the skin-color-cluster" and never asking "what about the hair-color-cluster"?

In reality, the reason is simpler: color-of-skin is a clear and popular ingroup / outgroup separator. Some people see black skin people, and they say "they are not like us", and it is a catalyser for the idea that color-of-skin is a good proxy: they like to think that they are different from them, especially if this difference rationalizes their opinions of them or justifies some of their biased conclusions (such as ultimate attribution error between ingroup and outgroup).

> Also, the claim that descent groups have different distributions of high intelligence genes doesn't necessarily have anything to do with skin colour ... Askhenazi Jews ...

That is correct. If the Black IQ question would had only one half of the arguments given in the case of the Akhenazi IQ question, I would give then the benefit of the doubt. I give the benefit of the doubt for the Ashkhenazi IQ question because there are way better arguments: a mechanism that explains why this group is a cluster, parallel factors such as specific genetic diseases, a non naive clustering such as "they look different, so their genes are different", a non naive clustering such as "let's put population thousands of kilometers apart in the same cluster, but suddenly draw the line even for neighboring population", ...

It still smells pretty fishy: why focusing on intelligence and not plenty of other stuffs? And "intelligence" is not even a "core component", it's an emergent property made of hundreds of characteristic: being able to do geometry and being able to do logic is as different as being able to digest milk and being able to run fast. Each of the component have their own advantages and disadvantages in plenty of very specific situations, it is just unrealistic that all the components have been favorised in one cluster and all have been disfavorised in another cluster. Even basic questions are just impossible to answer: is doing something that returns a benefice in the short-term smarter than doing something that returns a bigger benefice in the long-term (surely, whatever your answer is, you can change the factor between the two returns to find a situation where you don't agree with your answer anymore). So, I would give credit to a study that say "this cluster has better capacity for X", with X pretty limited, not obviously hierarchical and not so simplistic as a term like "intelligent".

But again, strangely, people interested in the Black IQ question are not really interested in the Askhenazi IQ question, and they scream at the "cancel of the science" when people consider rightly the Black IQ question to be pseudoscience, but don't care about how the Askhenazi IQ question is treated (unless they can instrumentalise it for their own purpose).