The term “Darwinism” is a beacon. If you see it or hear it, you know immediately that the source is almost certainly a religious fruitcake. No serious scientific discussion ever uses the word — “evolutionary theory” or simply “evolution” are typical terms.
Use of “Darwinism” exposes two errors of thinking: first, that evolutionary theory is the work of one person, Charles Darwin; and second, that this work can therefore be discredited or contradicted, as you might argue against “Marxism” or “Wesleyanism”.
The first fallacy is contradicted by straightforward historical fact, because the explanation of evolution was first presented in two independent papers to a meeting of the Linnean Society in London. Darwin had received an essay outlining the principles of evolution by natural selection from a younger, less famous scientist, Alfred Russel Wallace, and had been prompted to bring forward publication of his own theories.
The fact that two mid-Victorian scientists had independently worked out the methods and reasons for evolution is not an accident. It was something that was “in the air” at the time, and had Darwin and Wallace been run down by an omnibus when walking back from lunch at the Queen’s Head, it would not have been long before some other naturalist came up with the theory. In fact, Charles Darwin’s own grandfather, Erasmus Darwin, had published early materials on evolution in the 1790s, and a number of scientists and philosophers in the first half of the ninteenth century anticipated one or more aspects of the full theory that was worked out by Wallace and Darwin. (Darwin mentioned those he had been aware of in a preface to The Origin of Species.)
The second error of the evolution-deniers is more telling. They assume that the authority of Darwin is important. If Darwin can be shown to have made errors or to have had doubts, they think, then the whole theory of evolution is discredited. This type of thinking can even include the moral worth of the originator of an idea as an indication of the idea’s value.
Charles Darwin wasn’t a drunken, adulterous philanderer (Erasmus was), so the deniers lack the morality attack, but one story which emerges sometimes is that Darwin “recanted” on his death bed and re-converted to Christianity. Apart from the fact that it is a blantant lie, (if you need lies to bolster your faith, it can’t be worth much), it doesn’t fucking matter! Charles Darwin could have converted to Scientology and turned Down House into a retreat for demented movie stars, but that wouldn’t have decreased the truth of evolutionary theory by one jot.
The appeal to authority is exactly the difference between religion and science, and exactly why, in the end, religion always fails. When Darwin is proven wrong about something, as he has been, often, it doesn’t weaken science, it strengthens it. Much of what is asserted in the name of religion is unprovable, of course (and more importantly, un-disprovable), but the moment some religion or other makes a claim about a testable, real-world fact, you can be sure that reality eventually will trump belief. As the Earth goes round the Sun; as living species mutate and diverge; you learn the truth by asking questions, not by following the leader.