Why was Darwins theory of natural selection only accepted very gradually?
It wasn’t “only accepted very gradually”. Within about five years of its publication, there were few researchers left who didn’t accept evolution happens, and accounts for the diversity of lifeforms on the planet. A few wanted to keep people out of the picture. At that time, they were able to cite the absence of known evidence for transitional stages between non-human and human apes. However, that was blown out of the water later by the discovery of such remains as those of Homo erectus and Australopithecus. I’ve got an 1866 book taking that line from Oskar Frass, a German paleontologist. Although somewhat offended by the implications for human origins, he accepts that Darwin’s theory makes a great deal of sense in terms of the fossil record, his own specialty. One weakness with Darwin’s theory is a lack of understanding as to how inheritance actually works. That was worked out much more convincingly by Gregor Mendel.
