Aristotle's Refute of Empedocles Version of Natural Selection

Empedocles' discovery of the idea of natural selection left out a very important element, which darwin introduced. Aristotle was able to refute empedocles on that point because he got it wrong. Aristotle dismissed him ander therefore, he didn't see any good reason for supposing that the species had changed. I guess it can't then be that he assumes that animals, or that animal species, are eternal, just because nothing else has occurred to him except the alternative ea on the table, exactly.