I clarify:
Let’s say scientists can’t come up with solutions to global problems, AI gets out of control and turns almost everyone into paperclips during wars, and in the 2040s or 2050s, the surviving people (about a few tens of millions around the world or even less) gradually return to the level of intelligence of their distant ancestors?
As you have well noticed, I did not take into account that human evolution did not advance much intellectually and computationally, it was rather a matter of the variety of information that sharpened the human mind, to put it simply. Unfortunately, it is difficult to take all this into account.