Why was Peter Pettigrew Sorted into Gryffindor?

Peter Pettigrew was by no means courageous. He betrayed his best friends to save his own skin, blamed it on another of his friends, and faked his own death. He was also extremely afraid of other exDeath Eaters because they might think that he had wanted Voldemort's downfall to occur. Why, then, was he put into Gryffindor, "where dwell the brave at heart"?