What if the drugs we use, nicotine and pot and caffeine and sugar will be what determinans what middle species we evolve into? 

the caffeine addicts become elven in the night, moving with quiet speed and efficiency, awake at dawn to move with the creatures and staying silent as they move through the tangle of information cable forests

the sugar fields become dwarven cave dwellers, they live in basements that are buried beneath land fills and eventually rule the kingdom of the sunken jewels. Riches from earlier ages sifting down through the debris.

the nicotine addicts will become the gnomes; the coal shoveling workers of a filthy dystopia who slave for the cretins and the government drones  

the stoners are the farmers and the gatherers, the wise men and the witches and the children of the forest. They hold the secrets of the ancients and the dreams of the future.