If you refer to the American continent, the people lived there and that the civilizations as Columbus arrived. They had from our point of view unpleasant religi

If you refer to the American continent, the people lived there and that the civilizations as Columbus arrived. They had from our point of view unpleasant religions but otherwise were very able to live without the input from other continents. The continent allowed self sustainable human life. Compare Mars. If you want to implement Mars colony because of a possible nuclear catastrophe, the Earth after one would be more suitable for human life than Mars is now! Ditto for most "end of civilization as we know it" scenarios. All the concepts of "building a colony on Mars" assume the healthy Earth with a functioning high-tech civilization.