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.
Steve Connor Independent (UK) 09 August 2003Illegal incursions into the territory of uncontacted Ayoreo-Totobiegosode Indians in Paraguay are continuing. Landowners are erecting fences along tracks bulldozed illegally into the forest: this is the first step to clearing the forest and introducing cattle. The Ayoreo-Totobiegosode are the last uncontacted Indians south of the Amazon basin, and in recent years have been confined to an ever-smaller area. Mennonite farmers and Brazilian land-owners are buying up the forest in which the Totobiegosode live, and rapidly clearing it. Legal injunctions are supposed to protect a core area of 550,000 hectares of Totobiegosode territory, but clearance activity continues.
Survival International