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They are the amazing pictures that were beamed around the globe: a handful of warriors from an "undiscovered tribe" in the rainforest on the Brazilian-Peruvian border brandishing bows and arrows at the aircraft that photographed them.

Or so the story was told and sold. But it 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 "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, Jose 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 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 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."

But Meirelles appears, controversially, to have gone out to seek and find the uncontacted tribe in an area where it was known to live. According to his account, the Brazilian state of Acre offered him the use of an aircraft for three days. "I had years of GPS co-ordinates," he said. Meirelles argues the pictures were powerful and indisputable evidence to those who say isolated tribes no longer exist. But he is determined to keep the tribe's location secret. "They can decide when they want contact, not me or anyone else."