How small could a human scale down to?
Must be able to work stone, metal, and wood.
-If we can assume they evolved in a place with temperatures where they wouldn't freeze or cook to death, and figured out how to make clothes/fire to keep them warm so they could expand out into new areas.
-There are primates out there that are only ~5" tall. Along with a lot of mammals born hairless/nearly hairless of extremely small sizes and adult sizes.
-As I noted above, the smallest human I've found was less than 2' tall without mental disabilities, only minor physical disfigurements, capable of weaving garments for a living, walking unassisted, and died at 75 years old in a remote village of third world country.
-Humans wouldn't be dwarfed by everything in this scenario. I would also selectively scale down the flora and fauna of the world to give them similar conditions to what we have in the real world.
-Resources would obviously be much more plentiful