It's unlikely, for example, that these tribes have avoided any contact with developed societies, said Alexandra Aikhenvald, a linguistics professor at Australia's La Trobe University who has done extensive work in the Amazon.
"It is more a media newsmongering catchall word than any sort of scientific term," she said.
At least some contact probably occurred during the Amazonian rubber boom that lasted from about 1870 to the start of the First World War, a period marked by enslavements and massacres of natives.
Padre Ricardo lvarez Lobo, a Dominican priest who has worked with natives, said in an earlier interview with National Geographic News that those 19th- and 20th-century encounters probably created social taboos that send today's tribes fleeing from outsiders.
Survival International's David Hill said: "They're an uncontacted tribe in the sense that they live without contact with Brazilian national society or contacted tribes.
"We're not saying they've never had contact, just that those alive today live without it."
But John Hemming, a well-known author and expert on indigenous peoples, said he has no problem with the term "uncontacted."
"When a tribe gets to around a thousand people, it exhausts its resources in surrounding rivers and forests, causing it to split," he said, adding that a young chief will take three or four families to create a new village.
"Within a generation or two that group might have memories of outside contact, but no direct contact," he said.
Keeping Hands Off
As for what to do to best ensure the safety of such tribes, experts are similarly divided, said Nicole Bourque, a Glasgow University anthropologist.
"Some will say leave them untouched," she told the Scotsman newspaper.
"Others, probably the majority, will say more contact is inevitable. So the best thing you can hope for is managed contact, where you send an appropriate person in to prepare them for what might happen."
Hemming, however, told National Geographic News that strategies should be determined on a case-by-case basis.
"The big distinction is whether you are referring to people within an already protected area," he said.
Brazil and Peru are the countries with the greatest number of isolated peoples, perhaps 34 and 20 respectively, he said. Most of these groups are thought to be in forests that already hold protected status as indigenous parks or territories.
All countries that contain parts of the Amazon region—Bolivia, Peru, Ecuador, Colombia, Venezuela, and Brazil—have publicly announced policies of leaving uncontacted indigenous groups alone as long as possible. Such plans are made easier if the groups already live in protected territory.
But critics such the Lima-based rights groups AIDESEP and Racimos de Ungurahui say that developers routinely encroach on protected areas, especially in Peru.
"Theoretically, the only reasons they would make contact is if the Indians were facing a physical threat such as loggers, rumors of gold or diamonds, disease from adjacent tribes or, worst of all, a planned road near their territory," Hemming said.
Robert L. Carneiro, an anthropologist at the American Museum of Natural History, supports a hands-off approach.
He advocated a policy of creating maps of isolated communities' territory by consulting with neighboring tribes—and then making no efforts at contact to help preserve the pristine groups.
"In some way or another, it's inevitable that they will be contacted," said Carneiro, adding that he thinks the people in the FUNAI photos are related to the Aruak tribe, which he studied in 1960 and 1961.
"That's when anthropologists and medical services should come in to ensure their physical survival," he said.
Wade Davis is a noted author and a National Geographic Society explorer-in-residence. (The National Geographic Society owns National Geographic News.)
"There is no need to establish contact a priori just because of scientific curiosity," he said. "It doesn't give us a right to impose ourselves on these societies.
"If there are forces beyond our control, such as the will of nation states to penetrate rain forests with a pipeline, it does behoove us to make sure contact is as benign as possible," he added.
"That means, for example, using vaccination to ensure that pestilential diseases don't sweep through communities before benign contact is made."
Others say contact isn't a foregone conclusion.
"Calling something inevitable sounds to me like an excuse for not doing your best to do the right thing and stop it," said Hill, of Survival International.
The group takes the position that uncontacted tribes should be allowed to live in their own way on their own land, as recognized by international law.
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