If we went back to pre-civilization where people lived in bands of 200 people and lived sustainably on the food that each area provided, then that would require

If we went back to pre-civilization where people lived in bands of 200 people and lived sustainably on the food that each area provided, then that would require massive population reduction. At the level of population the planet can naturally support the pollution from fires wouldn't matter. It only matters when you scale it up to 9 billion of us, which is only possible because of technology.