Well, as a writer, I reserve the right to erase any race, continent, civilization, individual person, planet, or whatever from my work if I don't think it plays a part in my work, and to add, modify, or otherwise change anything else in any way, shape, or form that amuses me. It's MY universe, written for ME, and I am writing exactly and only the story I want, the way I want. As I've often said to people in discussions of books and reading: "I'm not writing for 'the reader'; I'm writing for ME. If the reader wants to come along and enjoy my story, that's fine, but what I'm doing is writing the stuff no one else will write for me."

Also, if you have hyperintelligent psychic mammoths and ninja sabretoothed tigers, you have just erased the race in question anyway, unless they're a chattel species to the HPMs or NSTs.