They are the people who turned their back on the industrialised world, having decided long ago to live in isolation or else having never made direct contact with outsiders.
But campaigners say that in the jungles of southern Peru, these so-called "uncontacted tribes" face an unprecedented threat from illegal loggersmoving into remote areas in search of rare mahogany trees.
They say the price of luxury furniture - mostly sold in the US - is a death sentence for these vulnerable people whose environment is being destroyed and who are being killed by disease and in clashes with loggers.
"Tens of thousands of tons of Peruvian mahogany are imported into the US for luxury tables, household trimmings and car dashboards," the Natural Resources Defence Council's Ari Hershowitz said.
"But Americans have no idea that buying mahogany contributes to the destruction of the rainforest and threatens the people who live there. People are dying - it is a crisis."
Experts say much of the logging takes place in the Tahuamanu rainforest, in areas specifically set aside for indigenous Indians and uncontacted peoples.
Here, mahogany trees can reach up to 36m. Each can be worth US$100,000 ($166,000) by the time the timber is sold in the United States.
Situated near the border with Brazil and Bolivia, this rainforest area is home to four tribes.
"There are two types [of isolated tribes]," the Amazon Alliance's Peter Kostishack said. "There are groups who have come into contact with outsiders but decide that is not for them."
There are also more literally "uncontacted" groups, known of only from evidence seen by other indigenous groups who have made contact.
"It's devastating in terms of their culture. But also, people living in isolation tend to be very vulnerable to illness and disease," he said.
The national resources council is suing three US timber importers, the Department of Homeland Security and two other agencies, accusing them of importing or permitting the import of illegal timber.
The US timber importers say trade in Peruvian timber is legal if the wood is accompanied with the documents provided by the Peru Government. But campaigners say the network of forged documents and the widespread corruption means that all of the mahogany imports from Peru must be considered questionable.
