Did they test rural Russian farmers too? How'd they do compared to Moscow or St. Petersburg residents?
Another thing that's overlooked is the huge jump in IQ with each successive generation that's exposed to structured schooling, decent healthcare, and solid nutrition. This tells you that either A) IQ tests aren't a great measure of intelligence, or B) intelligence isn't genetic, or even C) genetics aren't an inescapable, unchanging thing but can actually be modified.
No idea, I remember in the soviet union they tried to devise better tests for rural people but they were mostly central asians. They had problems with it, one of the examples was to see a series of objects and see what object was out of place.
The asian peasants were presented with a log, a hatchet, a hammer and a saw. They said no object was out of place. The researchers said the log was out of place because the others are tools. But the peasants argued that they could all be grouped as in things needed for woodworking.
Something similar when they showed pictures of some tools and fruits and how they should be grouped. The researchers expected the peasants to make two sets, one of tools and the other of fruits, but the peasants made various sets of a fruit and a tool to process it, like a knife to cut an apple, a hammer to crack a nut and so on.
So, even supposedly culture neutral tests can be biased.
Now, that was in the 1940s, and most people around the world nowadays have some kind of schooling and the gaps are not just when you compare a bushmen and people living in Switzerland.
African Americans, for example, score a lot lower than the Chinese in China who probably eat less nutritious food and are subject to a lot more harmful pollutants.
My take on it is that nurture is obviously important, you can improve the IQ of a population with better diet and health. IQ is just a number, but even if it's not true intelligence it shows you're good at doing things in industrial countries, it's cute that the soviet peasants couldn't get the test right but they would also be unemployable.
Genetics of complex traits like intelligence are still nebulous and even if theoretically we can do something about it, it will not be soon, but we shouldn't boycott people that study it as this knowledge may be important in the future.
For now we should invest in what is possible to improve, nurture as I said and promoting the end of consanguineous marriages in these African countries, as that is probably not healthy for their genes.