Delia Pacaya grew up in Peru's Amazon in a nomadic tribe that shunned contact with outsiders, but when loggers invaded the land she fled the virgin rain forest and settled in a tiny village.

Like many others born in the jungle, Pacaya says she felt threatened by loggers, who often cut beyond the reach of police. The result, environmental and human rights groups say, is the destruction of the Amazon and ancient tribal life.

"There were a lot of loggers and we were afraid," said Pacaya, now in her 20s, speaking Chitonawa and sitting in a three-sided hut, made from palm leaves, where her young son played and chickens pecked at the dirt floor.

Pacaya left her jungle tribe a decade ago and now farms a small plot on the Murunahua nature reserve in Peru's northeastern region of Ucayali. Most trappings of modern life escape her but some others, like nail polish and T-shirts, do not.

Although experts do not know for sure how many indigenous people have abandoned the rain forest and wound up in towns in recent years, they say former tribe members struggle to adapt and often fall to illnesses that their people had never before been exposed to.

"Uncontacted communities are in a very difficult situation. Most of them are being encroached on by loggers, among others, and their lives are in danger," said Beatriz Huertas, an anthropologist who often works with AIDESEP, a rights group.

Of more than 100 uncontacted tribes worldwide, more than half are thought to live along the Brazil-Peru border. In May, photographs taken near the border showed two Indian men covered in bright red pigment poised to fire arrows at an aircraft, apparently feeling threatened.

The photos reignited a debate between rights organizations and the government at a time when Peru is encouraging companies to explore for oil and gas in the jungle.