Here are some more reasons that haven't been mentioned yet. Keep in mind this is speculative on my part. 1. I read somewhere that the probable migration of nat

Here are some more reasons that haven't been mentioned yet. Keep in mind this is speculative on my part. 1. I read somewhere that the probable migration of native Americans over the ice-age land bridge between Asia and Alaska meant that the peoples lived for generations in climates too cold for new pathogens to evolve to infect humans. I guess because there weren't enough animals in the area with a sufficient genetic similarity to humans. So by the time people migrated south to warmer climates, they had no natural immunity to the diseases common in Europe. Another way to look at this is that Europe is closer to Africa. Africa is where most human diseases come from, because it's where humans evolved, and the diseases got to co-evolve with them. 2. Native Americans had better hygiene. And by that I mean they bathed regularly. Europeans were, by most accounts, sort of disgusting. They lived mostly in a cold climate (remember it was colder back then), and saw nakedness as unacceptable pretty much ever. They mostly just didn't bathe. Perhaps this is why the earlier failed Viking settlements had less of an effect on the native American population.