I would make a Facebook joke here, but... I think that they mean that these people have not been in direct contact with non-tribal people. It sounds like most

I would make a Facebook joke here, but... I think that they mean that these people have not been in direct contact with non-tribal people. It sounds like most of them are very isolated. Even the other tribes that have contact with the mainstream society seem to have little to no contact with these "uncontacted" tribes. This is mostly info I read on that website and related links, i.e. I'm not an expert.