From an article in Entertainment Weekly about Lost: One of the executive producers "cites Narnia as one touchstone for the kind of fantastical otherworld Lost is trying to create."
I just finished rereading Prince Caspian, and (spoiler alert), at the end, Caspian can be king of Narnia because he's a son of Adam. Because he's a Telemarine, and Telemarines originally came from Earth. An island in the South Pacific is described as the gateway, and the Telemarines themselves are descendants of a Fletcher Christian type mutiny. And at the end of the book, Aslan creates a doorway to send the Telemarines back to the island.
So I'm thinking, the Others have to be Telemarines.