One interesting way that creationism evolves is simplification.
A creationist argument usually starts off with a creationist reading something about science and misunderstanding it --- the original "mutation" that converts it into a creationist argument. So, when the creationist argument is first produced, it will have a certain amount of complexity and subtlety inherited from the ancestral scientific idea from which it evolved.
As it passes from one creationist to another, anything that makes it
simpler makes it easier to infect a creationist brain, and therefore is a selective advantage.
Unlike a genuine scientific idea, it doesn't have to be able to
do anything but propagate itself --- no-one ever
uses it for anything. And because it only has to pass between creationist brains, it doesn't have to be sophisticated enough to deceive anyone who knows anything about science.
So, like all parasitic organisms, it becomes simpler and simpler in form.
One interesting aspect of this --- I don't know if it has an analogue in biology --- is that this progressive simplification helps prevent the mounting of an immune response. When, for example, creationists are wrong about the neck of the giraffe, it would be much easier to debunk their nonsense if the called the
rete mirabile the
rete mirabile. If they call it a "special sponge", it becomes much harder for anyone to find out that they're wrong, because it would first be necessary to find out what the heck they're being wrong about.