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?


We already have the solution, the French made it in the 1800. We just lack the will to use them again.
No I assume they mean the problem of people being stupid assholes.
Which one?
https://en.wikipedia.org/wiki/Guillotine