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?
The only possible answer is that I would eek out an existence foraging for twigs and berries as a neolithic hunter gatherer. However, in my case I would only do that for several months before I died from a chronic health condition I manage with medication, so there’s that.
I don’t know if it’s really possible for us to go back to the stone age. There’s so much steel and iron lying around. I don’t really know much about metallurgy but I’m pretty sure I could figure out how to flatten some rebar into a blade if it was all I had to do all day.
We also have domesticated breeds of livestock and know how to raise crops.
So, at worst it would be some kind of modern iron age, neolithic isn’t really possible.
In the novel Star’s Reach, in a post-collapse society, one of the main characters is a ‘miner.’ Their mining guild basically tears apart old concrete buildings, by hand, with sledge hammers to extract the old rebar from them.