I don't think that there was much evolution in Middle-earth, especially with Morgoth's creatures. They were all bred, and inter-bred, according to his tastes. They weren't left to breed among themselves.
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But Melkor also was there, and he came to the house of Fëanor, and there he slew Finwë King of the Noldor before his doors, and spilled the first blood in the Blessed Realm; for Finwë alone had not fled from the horror of the Dark.
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