Incredible pictures of one of Earth's last uncontacted tribes firing bows and arrows

Skin painted bright red, heads partially shaved, arrows drawn back in the longbows and aimed square at the aircraft buzzing overhead. The gesture is unmistakable: Stay Away.

Behind the two men stands another figure, possibly a woman, her stance also seemingly defiant. Her skin painted dark, nearly black.

The apparent aggression shown by these people is quite understandable. For they are members of one of Earth's last uncontacted tribes, who live in the Envira region in the thick rainforest along the Brazilian-Peruvian frontier.

Thought never to have had any contact with the outside world, everything about these people is, and hopefully will remain, a mystery.

Painted: In a thick rainforest along the Brazilian-Peruvian border, these tribespeople are thought never to have had any contact with the outside world

Their extraordinary body paint, precisely what they eat (the anthropologists saw evidence of gardens from the air), how they construct their tent-like camp, their language, how their society operates - the life of these Amerindians remains a mystery.

'We did the overflight to show their houses, to show they are there, to show they exist,' said Brazilian uncontacted tribes expert José Carlos dos Reis Meirelles Junior. 'This is very important because there are some who doubt their existence.'

Meirelles, who despite once being shot in the shoulder by an arrow fired by another tribe campaigns to protect these peoples, believes this group's numbers are increasing, and pointed out how strong and healthy the people seemed.

But other uncontacted groups in the region, whose homes have been photographed from the air, are in severe danger from illegal logging in Peru and populations are being decimated.

Mystery: The tribespeople are likely to think the plane that took this photograph is a spirit or large bird

Logging is driving uncontacted tribes over the border and could lead to conflict with the estimated five hundred uncontacted Indians already living on the Brazilian side.

'What is happening in this region is a monumental crime against the natural world, the tribes, the fauna and is further testimony to the complete irrationality with which we, the 'civilised' ones, treat the world,' said Meirelles.

It is extraordinary to think that, in 2008, there remain about a hundred groups of people, scattered over the Earth, who know nothing of our world and we nothing of theirs, save a handful of brief encounters.

The uncontacted tribes, which are located in the jungles of South America, New Guinea and a remote and the beautiful and remote North Sentinel island in the Indian Ocean (the inhabitants of which have also responded to attempts at contact with extreme aggression) all have one thing in common - they want to be left alone.

And for good reason. The history of contact, between indigenous tribes and the outside world, has always been an unhappy one.

Human nature: One man points at the plane. Others ready their weapons

In our overcrowded world their very future hangs in the balance. Almost all of these tribes are threatened by powerful outsiders who want their land. These outsiders - loggers, miners, cattle ranchers - are often willing to kill the tribespeople to get what they want.

Even where there is no violence, the tribes can be wiped out by diseases like the common cold to which they have no resistance.

According to Miriam Ross of Survival International, which campaigns to protect the world's remaining indigenous peoples, 'These tribes represent the incredible diversity of humankind. Unless we want to condemn yet more of the earth's peoples to extinction, we must respect their choice. Any contact they have with outsiders must happen in their own time and on their own terms.'

As to who these people are, how they live their lives, what language they speak - we know nothing. 'Normally you can tell who tribes are by their language, how they wear their hair, how they adorn their bodies and so on, but in this case the photos don't allow us to get close enough to see,' says Ms Ross.

Hidden homes: The tribe's tent-shaped dwellings deep in the rainforest

When anthropologists first overflew the area, they saw women and children in the open and no one appeared to be painted. It was only when the plane returned a few hours later that they saw these individuals covered head-to-toe in red. 'Tribes in the Amazon paint themselves for all kinds of different reasons - one of which includes when they feel threatened or are aggressive,' Ms Ross says.

'And they are almost certain to feel threatened by or aggressive towards a plane, which was where the photos were taken from. They are almost certain not to understand what the plane is - perhaps a spirit or a large bird.

'The jungle is fundamental to their lives and survival. It's their home, their source of food, the source of their culture etc. Without it, they could not exist as a people.'

Contact is usually a disaster for these remote tribespeople, who live a life probably unchanged for more than 10,000 years. Even if the loggers do not shoot them (which they often do) or force them off their land, diseases against which these isolated humans have no resistance typically wipe out half an uncontacted tribe's numbers in a year or two.

Stay away: The anthropologists saw evidence of gardens, but exactly what they eat, how they build their huts and why they paint their bodies remains unknown

Ms Ross added: 'These pictures are further evidence that uncontacted tribes really do exist. The world needs to wake up to this, and ensure that their territory is protected in  accordance with international law. Otherwise, they will soon be made extinct.'

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