A tribe so isolated from civilization that they've never had contact with anyone from Columbus to us today has been found in Brazil.
http://news.bbc.co.uk/2/hi/americas/7426794.stm
Here they are trying to attack the plane
http://news.bbc.co.uk/2/hi/in_pictures/7426869.stm
You hear native Americans talk about how the white man stole their land and how they shouldn't have been there in the first place. Well, what you see above is how the indians would still be living today. That sort of thing is proof of what happens when whites don't have their hands in the development of an area. NOTHING HAPPENS. Entire populations remain, by definition, stone men.