Just a sec and you will see what I'm getting to.
Now here is the problem. If evolution is postulated to allow any creature to evolve into any other creature there's no reason to assume that such a change can't happen. But indeed most sane people would never postulate that it can. Creationists and evolutionists alike realise there's some inherent resistance to evolving. The question is only where does that limit lie. One end of the spectrum you could get someone to claim that a banana to human is possible and on the other you can get someone to claim nothing changes.
Seeing as most would fall somewhere in the middle we can run with something along that line of thought. A dog won't become a cat very easily. If you are lucky you can breed a few cats and a few dogs closer to each other and end up with something interbreedable that you can breed towards a cat or a dog. But that is unlikely and the further you go up the taxonomic classification tree the more unlikely it becomes. Then you still have the problem that you had both a dog and a cat to start off with so oops no real explanation for either.
Interesting dilemma so they come up with a solution. Everything diverged from some common ancestor becoming more specialized down the line. Evolution indeed has a direction it seems. But where are all these ancestors? We see all the evolutionary "trees" but what's the one thing they all have in common? They don't have branches! Only the leaves we see around us have names. The fossil record shows few if any ancestral lines. Most of the ancestors exist only in the imagination. Because of that nobody can really agree on what they looked like exactly and if you don't know that you can't really name them.
But now you'll say we do have very old fossils. Problem is they're the wrong thing and not really old enough. There's a bunch of dinosaur fossils, the supposed ancestors of modern birds and crocodiles, but none of them show a clear path towards birds or crocs. Instead they become extinct. Cue an even earlier terapod supposedly an ancestor of crocs and birds as well. It too becomes extinct at one point. Anybody seeing the pattern of holes here getting larger?
Now cue the cambrian explosion. This shows where every animal had its origin from so of course the evolutionists would be throwing a party over this one. Why aren't they? Because it shows the opposite. It shows most of the base forms of even todays animals but nobody is really sure what evolved into what. It looks more like raw base material that was then taken apart to make all the more complex creatures, just like the
mosaic platypus in fact. That's probably why most have chosen to ignore it just like there has been more time spent on explaining
tiktaalik than the platypus. The nice evolutionary tree looks more like a mingled bush by now. Interestingly the further back birds are traced the more they run alongside marine animals and before land animals. Can anyone say *cough* biblical *cough* creation in stages or more specifically sea creatures and winged birds of day 5. /runs for the hills/
In case there's still any doubt here I'll eliminate it. Evolution can be true for today. This is necessary for creation to continue existing but there is a separation of kinds due to specialisation. To apply it to the past you are making the assumption that nothing was created. This is a matter of necessity for the theory of evolution but there is no scientific basis for it. Darwin thought the gaps in the fossil record would eventually be filled but they became gaping holes while more nearly identical fossils were discovered. Gould proposed punctuated equilibrium to fill the gaps. Any conjecture to fill them with except God I guess. Dawkins will even accept alien creators clearly showing his bias is against a supernatural agent rather than from the soundness of the theory.