Reynold has said that the first people to think of and to hear of the idea of evolution were creationists. I am not inclined to agree. Sure, they openly claimed to believe in creationism. But, at the time, the church was very much in control. To do otherwise would have ended their careers -- and quite possibly invited a very unpleasant death. To anyone with an inquisitive mind creationism just does not make sense. Evolution has the advantage of making sense.
The church hierarchy was very interested in weeding out dissent. It could only do so, however, when it could recognize it. As the leaders did not think like scientists, they would not be readily able to recognize disguised heretics.
I believe large-scale evolution is held as a sacred belief. I also believe that if any scientist openly questioned it, his career would be ruined. Submissions to peer-reviewed journals would be returned unread. Now, this is testable in principle. But no scientist openly questions evolution. To test my idea, a group of scientists would need to do just that, and we could determine whether they continued to get published. The test will not be conducted. Who would put his career on the line in such a manner?