Antidotes are not data. We have no reason to believe from your story that your would not have got skin cancer if he had spent all his time in a cave. Or maybe he wouldn't have, because he would have died of something even worse at 45.

Science is trying to work this out, it is complex. We know that sun exposure both protects from and causes skin cancer depending on the study. This is a complex subject, the only thing I think I can safely say is don't get a sunburn.