Thanks, theland. There are two parts that confuse me... (well, at least!)
You say "never a new species". But it was humans who decided what "species" should mean. Basically, one kind of animal who couldn't interbreed with another. So, that can't be a surprise, that they don't, when it is our actual categorisation of it? Maybe we have just labelled things wrongly?
Also, with human evolution, neanderthals are classed as a different species from us, even though we did breed with them and continue their genes, until they died out. That has gone from one species to another.
Say it was possible for a cat to evolve into a dog, then we would have called them the same "species" in the first place. So that is technically right, by definition, but only because it's our definition.