I don't know that this is entirely true. I guess I can't really speak for dogs, fish, and ants, but religion seems to have developed with human intelligence. It's not really fair to call people like Plato and Socrates ignorant (depending on your usage of the word) because they believed in the supernatural. It made the most sense at the time. It's like someone 100 years from now saying Einstein was ignorant because his theory of general relativity failed to take into account a yet-undiscovered aspect of the universe.
Ignorance is simply lack of facts. There's nothing wrong with that that a textbook can't fix. It would be perfectly correct to call Einstein ignorant if some new data came up and showed him to be. Plato and Socrates were likewise operating from flawed knowledge.