I recently had a discussion with someone more expert on evolutionary theory than I. When I cited natural selection as the mechanism by which evolution works, he told me that natural selection is only one such mechanism, and that there others. By the time he finished talking, I'd forgotten to ask what I'm asking here.
What ARE the other mechanisms, if any?
(And a related question, while I'm here. I've been told that "survival of the fittest" is not an apt description of how natural selection works, and that a better description is "survival of the most adaptable". Is that correct?)