They live separate lives thousands of miles from one another yet they have many things in common. Now they have earned the dubious distinction of being the three most endangered tribes on earth.
There is a horribly familiar pattern that seems to follow the day when first contact is made between a "lost" tribe and the rest of civilised humanity.
Curiosity often gives way to fear. A roaming or nomadic lifestyle develops into furtive fleeing from one discovered settlement to a more remote part of the forest.
There is the all-too-frequent prospect of enforced relocation with the loss of culture, language and other skills honed by generations of ancestors and passed on by word of mouth.
Finally, there comes the indignity of government hand-outs, disease, alcoholism and the acceptance that you are no longer part of a tribe with its own mother tongue and unique way of life.
This has not yet happened to the three indigenous peoples identified by the charity Survival International as the most at-risk tribes in the world - but time is running out.
The Ayoreo-Totobiegosode live in the scrubby forests of western Paraguay and are threatened by logging, cattle ranching and over-zealous Christian missionaries from the United States.
On another continent, the Gana and Gwi people - who belong to the Bushmen of the Kalahari in Botswana - are under pressure to give up their ancestral lands to the lucrative diamond mining industry.
And several thousand miles away, on the remote Andaman islands in the Indian Ocean, the Jarawa tribe, who number perhaps fewer than 300, are fighting against a forest road that brings loggers, poachers and mainland settlers.
To mark the United Nation's International Day for the World's Indigenous Peoples - an annual event since 1994 - Survival International is publicising today the plight of these tribes to alert people to the loss of these cultures.
Stephen Corry, the charity's director, said that the tribes epitomised the threat to many indigenous people, including those who had yet to make contact with the rest of humankind - estimated to number about 70 tribes worldwide.
He said: "The Ayoreo-Totobiegosode and the Bushmen and the Jarawa live in totally contrasting environments across three continents, yet the racism and threats they face are startlingly similar ... Unless these tribes are allowed to live on their own land in peace, they will not survive."
The Ayoreo-Totobiegosode belong to the 5,000-strong Ayoreo tribe, which once occupied much of north Paraguay and south-east Bolivia. They are hunter-gatherers who hunt wild pigs and armadillos, collect wild honey and plant squash, corn and beans.
Jonathan Mazower, research co-ordinator at Survival, has visited the region and spoken to the Ayoreo who have come out of the forest. He said that the problem stems from the fact that the land is privately owned and is being sold for cattle ranching and logging.
The Ayoreo have also been subjected to continual encroachment on their ancestral homelands by Mennonites, a German-Swiss religious group that was encouraged to colonise the region in the 1930s by the Paraguayan government.
American fundamentalist missionaries have also attempted to convert the Ayoreo, using "evangelised" natives who have been sent back into the forests to make contact with their tribal members.
But Mr Mazower said that an unknown number of Ayoreo-Totobiegosode remained in the forest, resisting contact with outsiders. "From evidence such as footprints and abandoned huts, there are known to be several distinct family groups living in a wide area," Mr Mazower said.
He said that the tribe needed to be given ownership of the land. "They have a right to own that land so that they have the security to control their own future," he said.
The charity does not want indigenous people to be preserved in aspic, but to be given the opportunity to develop in their own way.
Mr Mazower said: "It must be their decision. The way they choose to make contact should be under their control, in their time and in their own way." Yet this is not happening. Mennonite settlers have bulldozed swaths of Ayoreo forest and the Totobiegosode living in the area have fled.
Mr Mazower said: "The Ayoreo-Totobiegosode have been fleeing incursions onto their land for decades, and have made it abundantly clear they do not want contact."
On the Andaman islands, a similar incursion is taking place on the traditional lands of the Jarawa, nomadic hunter-gatherers who have resisted repeated attempts at contact with Andaman settlers over the past 150 years.
The Jarawa are one of four indigenous tribes on the Andaman islands who have probably been there for thousand of years. Some geneticists believe they may even be a relic tribe from the original exodus from Africa of anatomically-modern human beings, some 70,000 years ago.
Miriam Ross of Survival said that the Jarawa probably numbered about 300. They live by hunting pigs and monitor lizards, and catch fish, turtles and other marine animals using bows and arrows.
The chief danger they face is from the Andaman trunk road, which bisects their land and brings poachers, loggers and settlers right into their midst. "The Andaman government had a campaign of forcibly resettling the Jarawa but that's now been abandoned. But the road still hasn't been closed," Ms Ross said.
In 1999, many of the Jarawa died after an outbreak of measles, to which they had no immunity. The virus could only have been brought into the area by outsiders. Ill-health has also plagued those Bushmen who have been resettled by the Botswanan government, said Fiona Watson, a member of the Survival team. "The Gana and the Gwi say that they are far healthier on their own land," Ms Watson said.
Yet the central Kalahari is rich in diamonds and mining companies are said to be nervous that indigenous people could claim mineral rights. Survival International believes this is behind the push to drive them off their land.
"They [the Gana and the Gwi] simply say 'this is where we live and this is our land'. They know that they can survive there," Ms Watson said. "We are not saying that they and the other endangered peoples should be preserved just for the sake of it. The Bushmen say they just want to be left on their own land and to be free."
For more information visit: www.survival-international.org
STRUGGLE FOR SURVIVAL
AYOREO-TOTOBIEGOSODE A part of the wider Ayoreo tribe, which once inhabited vast areas of scrub forest in Paraguay and Bolivia.
Totobiegosode means "the people from the place of a wild pig", an animal that is a valuable source of protein for the Ayoreo.
Their land is being systematically cleared from the south by European settlers and from the north by Brazilian ranchers keen to extend grazing land for their livestock. US missionaries are also trying to convert them to Christianity.
GANA AND GWI BUSHMEN These two tribes speak similar languages and live side by side in small, hunter-gathering communities. Although no one wants to live in the Kalahari of Botswana, their land is a target for diamond prospectors. Survival International believes the government wants to relocate them because they might claim mineral rights if they are given legal ownership of their ancestral lands.
JARAWA One of the four indigenous tribes of the Andaman Islands in the Indian Ocean. The Jarawa, like the rest of the Andaman natives, have fiercely resisted attempts at contact with outsiders. Their unique way of life is, however, threatened by a forest road running through their territory. Survival International has helped to thwart an attempt to forcibly resettle the Jarawa.Reuse content