Non-literal interpretation of Genesis goes back to the earliest years of Christianity, long before knowledge of dinosaurs or evolution.
In all the sacred books, we should consider the eternal truths that are taught, the facts that are narrated, the future events that are predicted, and the precepts or counsels that are given. In the case of a narrative of events, the question arises as to whether everything must be taken according to the figurative sense only, or whether it must be expounded and defended also as a faithful record of what happened. No Christian will dare say that the narrative must not be taken in a figurative sense. For St. Paul says: “Now all these things that happened to them were symbolic." --Augustine of Hippo, The Literal Meaning of Genesis[highlight added]