> claims to have a proof for an upper limit in how much "general intelligence" (that would be IQ) can change in the case of individuals or in the case of populations. In fact, the existing OBSERVED degree of IQ increases all around the world

I did not mention the Intelligence Quotient (which is subject to boosting). I mentioned the general intelligence factor (which is mostly innate). Using google scholar you can find many interesting articles about the general intelligence factor and its neurological basis.

Using google scholar with “general intelligence factor” I found this article that is cited 417 (it just struck my eye since the citations is extremely high for such a recent paper):

A Neural Basis for General Intelligence Science 21 July 2000: Vol. 289. no. 5478, pp. 457 - 460 DOI: 10.1126/science.289.5478.457

This one just struck my eye, but there are many more. In my opinion general intelligence factor has become beyond doubt – the question is now what the neurological basis for intelligence is.

I also think that we will not do this complex and interesting topic justice if we discuss it here.