But the arguments you often hear in defense of evolution sure make it difficult to avoid asking the question whether the scientific advocates of evolution really understand what they are doing. Jerry Coyne, in his Faith vs Fact, makes one such argument on page 33:
Further, oceanic islands like Hawaii and the Galapagos either have very few species of native reptiles, amphibians, and mammals or lack them completely, yet such creatures are widely distributed on continents and "continental islands" like Great Britain that were once connected to major landmasses. It is these facts that helped Darwin concoct the theory of evolution, for those observations can't be explained by creationism (a creator could have put animals wherever he wanted). Rather, they lead us to conclude that endemic birds, insects, and plants on oceanic islands descended, via evolution, from ancestors that had the ability to migrate to those places. Insects, plant seeds, and birds can colonize distant islands by flying, floating, or being borne by the wind, while this is not possible for mammals, reptiles, and amphibians.
What is disturbing is that the claim that the observations can't be explained by a creator isn't a scientific argument; it is a theological argument. And it's not a good theological argument at that. Since a creator could have put animals wherever he wanted, he could have put them where we have in fact found them. So the lack of mammals and reptiles on oceanic islands does nothing to disprove that a creator might have been responsible for their origin.
That does nothing to diminish the fact that the distribution of animals is very suggestive of the evolutionary scenario Coyne offers. If he had kept to that argument, and left out the lame theological argument, his case would be more persuasive. For adding a theological argument to a case that is supposed to be purely scientific suggests to the reader that Coyne doesn't really understand the difference between theology and science.
Stephen Jay Gould used to do a similar thing, deploying theological arguments in an allegedly scientific case for evolution. His favorite was to argue that bad biological design (from our perspective) was proof of evolution, since a creator would never make what appears to us to be a poorly designed creature (this is a broad paraphrase of Gould's original argument, which I am quoting from memory). Again, this is a bad theological argument, or at least an unsupported one, since Gould never gave any arguments as to why a creator would never create apparently poorly designed creatures. But the real point is the same with Coyne - the very scientists who are most insistent on keeping religion out of science insist on making theological arguments in support of their biological theories.