Reginald

I think that you are right in that Empedocles proffered a weird form of natural selection whereby there were originally many strange assemblages of chimeric creatures (lions with 10 legs, fish with fur, etc.) and only those that were viable survived to present day. I am not sure if Empedocles believed that those viable forms could give rise to new forms, or if he understood or elucidated the importance of crucial features of natural selection such as strong inheritance or the high fecundity of organisms.

Clearly, the Greeks entertained some interesting ideas that far surpassed any contemporary creation myths. However, I think that you have to wait until the 19th century to get something that would be recognizable as natural selection. Patrick Matthew offered a version very close to that of Darwin's, and of course Wallace is rightly considered a co-discoverer.