Its interesting how the course of events can be gently nudged in a new direction by the actions of just one person.
Well, Leonardo's work on fossils wasn't known very well but the "Brothers of Purity" (10th C Shiite group) did have pretty good desription in their encyclopedia. (They didn't do as well as Steno and the Mongols destroyed the entire intellectual infrastructure in the Islamic world; it still hasn't been rebuilt.)
Steno and Hutton were really good observers.