Following traditions of hundreds of years, the Nukak-Maku Indians roamed the jungles of southeastern Colombia, hunting game with blow guns and gathering berries, as oblivious to the modern world as it was to them.
Then one day in 1988, the two worlds collided when a group of Nukak men ventured warily into a town carved out of the jungle. Townspeople stared in disbelief at the naked Nukak; the equally astonished Indians stared back.
That first encounter was peaceful. The Nukak men felt so trusting that they brought out their women and children, who had been waiting in the bush.
But the aftershocks are devastating Colombia's last nomadic tribe. Cut down by diseases brought by settlers, lured by the conveniences of the modern world and caught in the cross-fire of civil war, the Nukak are being driven along a path to extinction that more than 100 other Indian tribes across the Amazon region have traveled.
Missionaries estimate at least 1,200 Nukak roamed in groups of 30 or so when that first hesitant contact was made in Calamar. Fifteen years later, their number has plunged to about 380, the Health Ministry says.
Anthropologists believe that only a few dozen Nukak still live deep in the jungle, relatively untouched by civilization. "At this rate, in a very short time, there will be no more Nukak," said Humberto Ruiz, an anthropologist who has studied the tribe. "They will be a vague memory."
The Nukak are a branch of the Maku family of nomads who have lived in the northwestern Amazon River basin of current-day Colombia, Peru and Brazil for thousands of years.
Contact with settlers brought influenza, for which the Nukak had no resistance, and pneumonia caused many deaths. At the same time, deforestation has removed their traditional hunting grounds and led to malnutrition.
Adding to the pressures, leftist rebels and right-wing militias have been battling in the Indians' homelands for control of coca, the base ingredient of cocaine, which flourishes naturally and provides the warring groups with huge revenues.
No Nukak has been reported killed, but the clashes have terrified them and caused some to flee their ancestral grounds.
One clan of 10 families left its camp near a village on the edge of their reservation in January because of the fighting. "We were afraid, afraid of the explosions," said Yeuna, the clan's leader.
The clan is now at a makeshift camp in a jungle clearing near the village of Barrancon, a half-hour boat ride upriver from San Jose del Guaviare, the provincial capital of Guaviare state.
Rice, lentils and yucca are delivered every 15 days to the camp, where colorful hammocks swing from trees whose dense leaves filter the sun's rays. The food has led to ailments because of the change from the Indians' traditional diet of meat, fish and berries. But more critically, it is increasing their dependence on the outside world.
Hugo Quijano, an aid worker, said the help is undermining Nukak culture but added it is needed because the clan lacks the wide areas it needs for hunting and fishing. "We are trying to limit our contact with them as much as possible, but the conditions of the area they are in make that difficult," he said.
Yeuna's clan is gradually trading nomadic ways for a more sedentary existence. They are learning Spanish, wearing T-shirts and baseball caps, and drinking Coca-Cola.
Still, it maintains traditions. The women pluck their eyebrows and cut their hair very short. The men, who are lean and practically hairless, sometimes leave camp to fish or hunt monkeys.
During a recent visit by a reporter, Nukak children ignored a radio in the camp and became mesmerized by a woman of the clan as she broke into song in the Nukak's native language. More than half the 40 Indians in the camp are children.
There are no elders; they have all died. The oldest known living Nukak is estimated to be in her early 40s. Ruiz said the Nukak used to live into their 60s, but contact with outside diseases has taken its toll.
There is little consensus on how to preserve Nukak culture while allowing those who want to integrate into modern society to do so. "One cannot force a group to conserve itself, like an artifact in a museum," Ruiz said.
Assimilation appears to be unstoppable. Most Nukak clans -- like Yeuna's -- are drifting closer to towns, where life is seen as easier than living hand-to-mouth in the jungle. The Indians are still susceptible to the flu, but access to health care means that it is less likely to turn into pneumonia and kill them.
Once they leave the old ways, it's hard to go back. Manuel Garcia grew up with his Nukak clan, but after both his parents died when he was 8, he was adopted by a settler in San Jose del Guaviare. After turning 18, he reconnected with a group of Nukak.
"I tried to live with them in the jungle, but I only lasted six months. I had to leave. I just didn't have the same toughness that they did," said Garcia, who is now a health worker and is helping Yeuna's clan.
Yeuna, sitting in a hammock and surrounded by his five children and his pregnant wife, insisted that he wants to lead the clan to their ancestral lands.
"We want to go back," he said in broken Spanish. "But we are waiting for them to stop fighting."