>>Why do so many features in living things look like the result of small, incremental changes?<<
And I think that is a valid question. But it is not really related to the former question, except that both deal in perception of facts, as opposed to facts themselves.
It's true. Prior to Newton, people gave unrelated explanations for the orbits of planets and the falling of objects. Some perceptions lead to increased understanding, and some perceptions lead nowhere. Just depends on what your goals are in organizing your perceptions.