Respuesta :
The correct answer is that they have built up immunities!
The illnesses which lead to the death of many native Americans have been present in the old world for a long time already that many people have already died from them. Those that didn't die were immune and passed on this immunity to their children.
The illnesses which lead to the death of many native Americans have been present in the old world for a long time already that many people have already died from them. Those that didn't die were immune and passed on this immunity to their children.