“overwhelming majority”
Well, those words are key, aren’t they? all it takes is a “small minority” for evolution to work.
True enough, but in that regard, intelligent design is a more rational theory.
I can, for example, imagine the types of mutations that would slowly change a reptilian scale into a more feather-like structure, and give it's bearer certain advantages in flight characteristics. By that same token, even beneficial mutations typically come as a trade off and have some disadvantage for the advantage they provide. If it was only one individual, or even just one brood that bore the initial mutation, the chances of it/them surviving and succesfully transmitting the mutation would be more probable if they were "meant to."