well, it was all bullshit! From Gawker:
Our own Alex Pareene was so money when he called bullshit on that supposedly unknown tribe photographed in the Amazon. It was all a ruse by a concerned environmentalist! "[I]t has now emerged that, far from being unknown, the tribe's existence has been noted since 1910 and the mission to photograph them was undertaken in order to prove that 'uncontacted' tribes still existed in an area endangered by the menace of the logging industry. The disclosures have been made by the man behind the pictures, José Carlos Meirelles, 61, one of the handful of sertanistas— experts on indigenous tribes—working for the Brazilian Indian Protection Agency, Funai, which is dedicated to searching out remote tribes and protecting them."
"In his first interviews since the disclosure of the tribe's existence, Meirelles described how he found the group, detailed how they lived and how he planned the publicity to protect them and other tribes in similar danger of losing the habitat in which they have flourished for hundreds of years.
"Meirelles admitted that the tribe was first known about almost a century ago and that the apparently chance encounter that produced the now famous images was no accident. 'When we think we might have found an isolated tribe,' he told al-Jazeera, 'a sertanista like me walks in the forest for two or three years to gather evidence and we mark it in our [global positioning system]. We then map the territory the Indians occupy and we draw that protected territory without making contact with them. And finally we set up a small outpost where we can monitor their protection.' [...]
"What he was looking for was not only proof of life, but firm evidence that the tribes in this area were flourishing—proof in his view that the policy of no contact and protection was working. On the last day, with only a couple hours of flight time remaining, Meirelles spotted a large community.
"'When I saw them painted red, I was satisfied, I was happy,' he said. 'Because painted red means they are ready for war, which to me says they are happy and healthy defending their territory.'" [Guardian via Dana]