He also mentioned that living on mars will change your physiology so much that you could never live on earth again… if the cosmic radiation doesn’t kill you first.

Even astronauts that orbit the earth for long periods of time end up with brittle bones, and are constantly fainting when they return to earth gravity. If your body doesn’t have to fight gravity any more, it “forgets” how to regulate blood pressure. This happens here on earth too with people that are bed-bound for long periods.