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.

However, religious people today are overwhelming ignorant because there is so much evidence to the contrary. Sometimes I wonder if even the pope believes that God is real, or if he fakes it so his life of celibacy wasn't all for naught. Otherwise, I think people are afraid to admit that what they believed their entire lives was actually untrue.