Why does Enzo envy people’s tongue and thumbs?The Art of Racing in the Rain

Enzo believes there was a conspiracy against dogs to limit their powers. Enzo thinks that men domesticate dogs out of fear that dogs will develop thumbs and smaller tongues thus allowing them to become superior.Enzo believes this is the reason that dogs must, "live under the constant supervision of people, and are immediately put to death when found living on their own."