Take a good look at this photo... The Brazilian government says it was taken to prove the existence of "uncontacted" tribes living in the Amazon... And since they've been proven, now their lands can be protected from industrial development. There is also concern that the people themselves may not be resistant to many diseases. It's fascinating, and I can hardly get beyond the existence of the photo, much less the people. I keep looking at it and wondering what their lives are like, what they used to paint themselves in such brilliant colors, how they explain the existence of the plane. National Geographic writer Scott Wallace has trekked South America to discover uncontacted tribes like this one, and joins us today.