Photographs released last week of a tribe in southwest Brazil have put public attention on uncontacted people, of which about 100 are believed to exist.

Those tribes, most of whom live in the Amazon, are often described as living fossils of Stone Age life, flash-frozen in time. Such descriptions are unfair: We don't really know how people lived in the Stone Age, and there's no reason to think that uncontacted cultures have not continued to evolve in their own unique ways.

What can be said, however, is that uncontacted people are threatened by disease and development. If they're going to survive, they need help from the outside world.

Wired.com takes you on a tour of uncontacted people and the issues facing them — and us.

(Editor's note: the machete in the photograph was likely obtained through trade with Indians who have made contact.)