This is exactly the sort of example needed for evolutionists to point to to say "see, it can happen in terrestrial time periods". A puny 50k years, and we appear to have multicellular creatures which evolved to not need oxygen. That's way more than mere adapting, that's a fundamental, radical change.
You may be able to impress the undecided by-standers (and that's important). Don't count on winning over anyone who's decided that evolution doesn't fit into their world, at least not with rational arguments.
P.S. This is meant as a comment on the limited reach of arguments in convincing. I don't want to start a discussion on creationism.
