A large number of Yahoo's "Most Emailed Photos" are of an uncontacted indigenous tribe of people who live on the border between Brazil and Peru.
But the photos attached to the BBC report of the story are much larger and better.
According to the BBC story, "More than half the world's 100 uncontacted tribes live in Brazil or Peru, Survival International says."
The Guardian's report on hidden tribes does not add significantly to the BBC story.
Finally, here is the AP coverage.