The last stone-age Indians: life for an isolated tribe deep in the amazon rain forest hasn't changed in thousands of years. Can it survive?

For Domingo Neves de Souza, it was only a half-hour's walk to the edge of the unknown. Two years ago in September, he ventured out from the Brazilian rubber plantation where he lived and pushed deep into the Amazon to go fishing with his two daughters and three of their friends. Hidden in the thick forest, de Souza had long been told, were naked Indians who lived just as they had for thousands of years, eating what the forest grew and hunting with bow and arrow. But for the 33-year-old rubber-plantation worker, these Indians were an invisible presence, felt more than seen. Until that day, when they stepped out from the trees.

"Papa, there are people coming," de Souza's daughter, Francisca, 14, had yelled as five Indians ran toward them. "Run, my girl, they'll kill you," de Souza cried. The arrows flew. One hit his left side. Another pierced his back. As Francisca later reported, she knew as she was fleeing that she'd never see her father alive again.

An hour later, a posse of plantation workers headed out to the spot. But the Indians that Francisca and the other children described had vanished, as if absorbed back into the forest. Who could they be? Were they indios bravos--"wild Indians"--as the locals call isolated tribespeople?

THE FIRST SIGN OF DISCOVERY

Stories of the incident eventually reached Sydney Possuelo, 59, the Brazilian government's leading authority on isolated Indians. Possuelo traveled to the area where the murder occurred, in the far western state of Acre, but not to solve the crime. He was no police detective, nor did he have much sympathy for ambushed pioneers. He knew that from Brazil's first days, white settlers had ruthlessly slaughtered Indians, burning their villages and abducting their children to work as slaves. Possuelo's interest lay in discovery; a murder by unclothed Indians has often been the first sign of a previously uncontacted Amazon tribe. If isolated people were indeed hiding nearby in the forest, Possuelo wanted to find them--to offer the tribe protection, for as long as possible, from the modern world.

Anthropologists believe the Amazon shelters the world's largest number of still-isolated Indians. Since the 1970s, Brazil's government has counted 50 rain-forest sites with signs of indigenous settlement, many of them spotted by air. Possuelo believes these traces indicate the presence of about 15 tribes that have never been studied or, in some instances, even identified by scholars.

During his 40 years as a sertanista, or Indian tracker, Possuelo has located seven such tribes himself. And he argues that virtually every Indian band touched by Brazilian society has been destroyed as a result. Rather than benefiting from the medical and technological advances of civilization, they have withered from disease, slavery, alcohol consumption, and the greed of Brazilians. Throughout this century, even well-meaning whites have destroyed tribe after tribe, usually by introducing germs and diseases against which the Indians have no defenses: chicken pox, malaria, tuberculosis, even the common cold. When Europeans first reached Brazil about 500 years ago, the Indian population was an estimated 1 to 6 million. It is now 300,000.

Possuelo argues that much as endangered turtles and jaguars deserve government protection, Brazil's Indians also need sanctuaries. Ranged against him are powerful voices coming from those who covet Indian lands and resources--petroleum, mining, and agricultural businesses, or pharmaceutical companies searching for forest-based cures. Even missionaries--like Don Pederson of the New Tribes Mission, a Florida-based group--want to invade the Indian territory. Primitive tribes are plagued by malaria and dental problems, troubles for which the non-Indian world has solutions, Pederson says. "Would you say that you should leave people in dire straits in the ghetto because that's their area, and to go in and provide economic or health assistance is wrong because it would change their lifestyle?" he asks.

IN SEARCH OF THE KORUBU

This past July, I joined Possuelo on a journey into the depths of western Brazil's rain forest, where he hoped to contact the elusive Korubu. Three years ago, when he had first met them in the remote Javari Valley, they had somehow gotten separated from their tribe about 60 miles north and were being hunted down by local settlers. A fierce people, the Korubu were nicknamed the caceteiros, or "head bashers," for the way they killed enemies. They had already dashed with local Brazilians, once murdering two workers from the Petrobas oil company as hundreds of co-workers watched in horror.

Possuelo made four forays into the jungle in 1996, each lasting about 10 days, before a small group of Korubu emerged from the leaves to meet him. They were naked and painted with rust-colored patterns on their faces and chests. Short and sturdy, the Korubu walked with their legs wide apart, as if to frighten off animals, and they appeared robust and confident, masters of their small universe.

Getting to that universe hadn't gotten easier in the three years since then. We traveled first to the remote outpost town of Jordao, 120 miles by river from the Peruvian border and eight days by boat from the nearest Brazilian city. After a night's rest, we headed to Jordao's airport, a ribbon of dirt running through the center of town. There, while we waited for the clouds to lift, Possuelo sat on the wheel of a single-engine plane and listened as locals complained about being driven from the forest by indios bravos.

AN OCEAN OF GREEN

With the sky half-clear, our small plane finally took off, trundling in and out of the clouds like a growling, airborne dinosaur as we passed over miles of uninterrupted treetops. To my eyes the rain forest seemed like an ocean of trees, stretching green as far as we could see in every direction.

We flew north to Tabatinga, a ramshackle town located at the point where Peru, Colombia, and Brazil converge. There, we began our long journey by boat toward the Javari Valley. Along the way, blue-and-silver dolphins turned cartwheels alongside the boat, and even though a malaria epidemic was sweeping the region, Possuelo was cheerful.

Finally, one hour past midnight and 19 hours after our river trip began, we chugged up to a government outpost, our final destination. With lights out and the boat's motor silent, I caught the first movements of the local symphony. Bats fluttered overhead, locusts rattled like maracas, and owls sang a haunting chorus. From far away came calls I could not identify. Yet they sounded as if they were being repeated and perhaps answered, in the Morse code of the jungle. Could that be the Korubu?

At daybreak, sounds came from across the river. Emerging from our hammocks into the sunlight, we saw six Korubu, square shouldered and tan. One man wore a polo shirt, but the rest were naked. "Bina! Bina!" a man's voice called over the water, steady and insistent, trying to hail our translator whom he knew. "We're hungry. Go hunting for us."

SICK AND HUNGRY

A group of Korubu, many of them suffering from malaria, had been camped across the river for days and had little to eat. Bina hopped into a speedboat docked next to the outpost and disappeared into the Indian areas with Possuelo and a hunting party. He returned a few hours later with crocodile and wild boar carcasses lying on the speedboat floor. The Korubu swarmed to the boat and surrounded it in bursts of sound. Their voices were loud; to my ears, their language sounded bold, even harsh. Two Korubu women slid down the riverbank, splashing water over their children to cool down. As the group took us in, they seemed almost angry. "Pawa! Pawa!" some declared. Suddenly, one member of our group unzipped a fanny pack and produced a soup spoon. The anger dissolved into wide smiles.

The following day, we returned to the outpost. There we found Xikxu, the tribe's patriarch, and some women, who had emerged from the forest when he called. One carried a child over one shoulder and a monkey over the other. "Pawa, pawa," two of the Korubu women said, checking my pockets for spoons.

A young mother, baby perched on her hip and nursing, approached me slowly and touched my curly brown hair. "Maya Washeman," she said, pointing to herself. She pointed to another Korubu woman with a scar across her cheek. "Maya Mona," she said. She gestured at a sad-eyed woman sitting away from us. "Maya Doni," she said. Then she pointed at me.

"Maya Diana," I told her. I wasn't quite sure what "Maya" meant, but it seemed appropriate.

A STONE-AGE WISH LIST

The women carried empty pots and bowls, showing them to me in a wordless version of a shopping list. This time, I understood: the Korubu live in a pre-metal age, and 8,000 years is long enough to wait for a spoon. I promised not to show up again empty-handed.

On the third day, Possuelo and I paid the Korubu one last visit, this time with some malaria medicine. It was cool under the trees, and quiet. Washeman touched the nape of her son's neck, putting my hand there so I could feel his fever. A few feet away, Maya, the clan's matriarch, whimpered quietly. She, too, was burning up, and we gave her quinine-based pills in water to drink. Next to her, Doni sat sad-eyed and quiet. Recently, she had given birth, only to see her baby die just minutes later.

Xikxu scraped a rope-thick vine back and forth over a grater. A liquid the color of worn leaves trickled down. The grater was a wooden club like a miniature baseball bat, flattened on one side, with the chewing end of monkeys' teeth sticking out of the wood. "Sometimes they drink hallucinogens before they kill somebody or go to war," Possuelo told me quietly in Portuguese, passing the drink. I took a sip. It had the sour, very green taste of something unripe. After a few minutes, Possuelo asked Bina about the juice. Bina revealed that the drink was just a social one.

Talking to Possuelo, the Korubu laughed over their first meeting with him and remembered hiding when his small plane flew overhead. Xikxu asked Possuelo why he smoked cigarettes, and Possuelo said it was something Brazilians do socially. Washeman suddenly asked Bina a startlingly frank question: "How do you have sex?" The question took us all aback. "We do it at night," Bina responded. As they listened, the Korubu said "mmm," in the same way Americans say "uh-huh."

Sitting there in the jungle, I began to wonder if the Korubu could truly fathom the difference between our world and theirs. If history proved any guide, I thought, that knowledge, when it came, would shatter them.

A month after I left the forest, Possuelo phoned me. The Korubu had recently watched an anaconda pull one of their children, a 3-year-old girl, underwater, he reported. Though they had searched frantically, she never surfaced. The tribespeople had wept for her in the place where she died, day after day.

And so, lingering in my mind after my trip to the Javari rain forest was a question: Why preserve a life of hardship? But like gears in a machine, one question triggers the next. What kind of life would the modern world give them?

RELATED ARTICLE: Fighting for their futures.

For the world's 300 million indigenous people, descendants of the first known inhabitants in more than 70 countries, contact with the outside world has often meant persecution, eviction, disease, and death.

But in recent years, native people have begun to use the weapons of the modern world--public-relations campaigns and lawsuits--to fight for their land and resources.

Among the recent actions:

* In Ecuador, the Cofan Indians sued Texaco, asking $1 billion for damage caused by the company's oil-drilling operations in their native rain forest. They charge that shoddy drilling practices created massive oil spills, destroying their food supply. Texaco says it followed Ecuadoran environmental regulations and denies its drilling operations caused the harm. The suit is still pending.

* In Colombia, the U'wa people threatened mass suicide if Occidental Petroleum drilled for oil on their lands. Bowing to worldwide negative publicity, Occidental scaled back its plans.

* Native American farmers and ranchers sued the U.S. Agriculture Department this fall, seeking $19 billion in damages, alleging a 20-year history of discrimination in the granting of loans.

* Australia this fall expressed public regret for past mistreatment of its Aboriginal minority. Prime Minister John Howard called the era the "most blemished chapter in our national history."

* Native Canadians have found a willing listener in the Canadian government, which is currently negotiating hundreds of land claims by native people. Already, the Canadian government has agreed to turn over a 15,500-square-mile section in Newfoundland to native tribes. In another province, Manitoba, agreements are being negotiated to give back nearly 45 million acres to tribes.

SOME SETBACKS

But even the victories of native peoples are often tempered by defeat. Until the 1970s, many Aboriginal babies were taken from their parents at birth in the belief that it was best for them to be assimilated into white culture. On the same day that Australia apologized, an Aboriginal woman who was taken from her mother lost her court battle for damages.

And recently in Guatemala, despite a United Nations report concluding that the army had waged a brutal war against Indians for decades, a vote that would have extended more rights to Indians failed. One of the reasons? A high Illiteracy rate among the Indian population meant that few even knew that the vote was scheduled.

DIANA JEAN SCHEMO is the former chief of The New York Times Rio de Janeiro bureau.