It is only because the difference between the
rate of change in a static universe and the
rate of change in an evolutionary one is that
between zero and very nearly zero that the
creationists can continue propagating their
folly.
Well, there's still another part sneaking past the fact that biological differentiation occurs at geological time scales: We haven't been around long enough to witness and record an actual "smoking gun" event, that clearly demonstrates the emergence of a completely new plant or animal.
We're aware of things like the three-toed horse, and we know they used to exist. But that's just a small difference on an animal that still exists, and other than that whole thing with the toes, it's still pretty much the same thing. We've seen lots of animals disappear, but nothing replacing them.
Maybe insects are a ripe branch of animals that will bear some fruit, since their life cycles are so short, but otherwise, for the most part, modern theory points out that not only will none of us see a new, radically different class of creatures emerge within our own lifetimes, but not even within the projected limits of our modern civilizations and their effective capacity to record history will we be likely to observe such an event.
So, neither since the start of our recorded history, nor until after the history we do manage to record starts to disappear beyond the possibility of rediscoverable recognition by the next order of civilization which may arrise, shall a truly different creature spring forth from the free-for-all of biological propagation.
In other words, we've never actually experienced a period where a certain life form did not exist and then emerged from some other thing, and we'll probably never get a chance to see such a thing happen, not in 5 million years, and even if we do spot a new previously undiscovered animal, and it turns out to be an example of the emergence of a new and distinctly different animal, even if it makes it into the history books, and the animal is hardy enough to persist in nature, our history books won't last forever, and after we're gone, the next civilized culture (human or oherwise) might not find them, and learn to read them before they disintegrate into unrecognizable ash and dust. But we know it's there. We're sure evolution isn't just a theory.
And so too, are we faced with a scenario, whereby even if hypothetical civilized lizard people of the dinosaur era had been there to witness a new class of rodents spring forth, the records of their culture that we do find might not include that one passage. And so too, with civilized trilobite scholars, if they were there to see the original sharks and amphibians emerge, and wrote it down, we'd probably never find that chapter in the trilobite bible where they realized what they had just seen.
That's a tough idea to pitch to people, and in casual conversations at dinner parties, it's devestatingly easy to stymie people who try to explain it.