SAN JOSÉ DEL GUAVIARE, Colombia — Since time immemorial the Nukak-Makú have lived a Stone Age life, roaming across hundreds of miles of isolated and pristine Amazon jungle, killing monkeys with blowguns and scouring the forest floor for berries.

But recently, and rather mysteriously, a group of nearly 80 wandered out of the wilderness, half-naked, a gaggle of children and pet monkeys in tow, and declared themselves ready to join the modern world.

“We do not want to go back,” explained one man, who uses the sole name Ma-be, and who arrived with the others at this outpost in southern Colombia in March. “We want to stay near town. We can plant our own food. In the meantime the town can help us.”

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The Nukak have no concept of money, of property, of the role of government, or even of the existence of a country called Colombia. They ask whether the planes that fly overhead are moving on some sort of invisible road.

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“The Nukak don’t know what they’ve gotten themselves into,” said Dr. Javier Maldonado, 27, a physician who has been working with them.

The rest of the fascinating story from the New York Times. And yes, that kid is biting into a monkey head.