DOROUGOK, Indonesia — The older man wore just a loincloth, revealing taut muscles and leathery skin from decades of living deep in the rain forest. Like other members of his tribe, he was covered head to toe in tattoos. Though he appeared strong, he had a pronounced hunch, and a cough from smoking too much tobacco.
The man, Teu Kapik Sibajak, grabbed his ax on a recent morning and went off through the forest to chop down a sago palm tree. Mr. Kapik delivered precise blows before he and a few friends stooped down and rolled pieces of the thick, heavy trunk toward his house. “Hard work, this!” he announced.
But the effort would be worth it: The tree’s leaves provide the roof for his wooden long house; its starchy insides can be cooked and eaten, or fed to the household’s pigs, ducks and chickens.
Mr. Kapik and his wife, Teu Kapik Sikalabai, are among the last of the Mentawai people living traditional lives deep in the forest on the remote island of Siberut.
The Mentawai tribe, which today numbers around 60,000, is a rare Indonesian culture that was not influenced by Hindu, Buddhist or Muslim currents over the last two millenniums. Instead, their traditions and beliefs strongly resemble those of the original Austronesian settlers who came to this vast archipelago from Taiwan around 4,000 years ago. If the tribe’s culture disappears, one of the last links to Indonesia’s early human inhabitants will go with it.
Their physically demanding lives now pose a challenge for their children. “They have to work although they’re already very old, work until they can’t work anymore,” said Petrus Sekaliou, the Kapiks’ son. Mr. Sekaliou wears Western clothing and, unlike his parents, can communicate in fluent bahasa Indonesian, the national language.
Mr. Sekaliou, 42, lives in Mongorut village on the outskirts of the forest, a brisk 90-minute walk from his parents. He farms and does odd jobs there, and tries to visit his parents every weekend.
When his parents can no longer fend for themselves, Mr. Sekaliou said, his plan is to leave his children in the care of his wife, and move back to the forest until his parents die. The alternative — moving his parents to the village, where motorbikes whir and teenagers banter on cellphones — would be too wrenching in their old age.
“They’re happy in the forest,” he said. “This is what they know.”
Mr. Kapik, his father, is of a special class known as Sikkerei — shamans, forest healers and keepers of the Mentawai’s animist faith. He and his wife insist they are not going anywhere.
“I would never move from here,” Ms. Kapik said.
Since arriving on the island of Siberut around 2,000 years ago, the Mentawai people had limited exposure to the outside world. It wasn’t until Indonesia gained its independence in 1945, and the new country’s leaders sought to turn this archipelago into a nation with a common language and culture, that the Mentawai culture began to be fundamentally transformed.
By law, all citizens of Indonesia had to accept one of Indonesia’s officially recognized religions: Islam, Christianity, Catholicism, Hinduism or Buddhism. But the Mentawai, like many other Indonesian animist tribal peoples, didn’t adopt a state-recognized religion.
In 1954, the Indonesian police and other state officials arrived on Siberut to deliver an ultimatum: The Mentawai had three months to select either Christianity or Islam as their religion and cease practicing their traditional faith, which was considered pagan. Most Mentawai selected Christianity, in part because Islam forbids the raising of pigs, which is central to their culture.
Over the next few decades, Indonesian police officers worked with state officials and religious leaders to visit Mentawai villages to burn traditional headdresses and other items the tribe used during religious rituals.
The Kapiks fled deeper into the forest to avoid the state’s incursions, without success. Ms. Kapik recounted how the commander of the local police had once forbidden them to get tattoos or sharpening their teeth, both customs among the Mentawai.
“It made me so angry,” she said. So she rebelled.
In the late 1960s, Ms. Kapik said, she decided that she would ignore the ban and tattoo her legs. The police commander, Nikodemus Siritoitet, noticed the new tattoos during one of his visits to the Kapiks’ home in the forest. He punished her by forcing her, without pay, to cultivate land in the hot sun for a week.
“It was miserable,” she said. “I was never brave enough to get tattooed again.”
Reimar Schefold, a Dutch anthropologist who lived among the Mentawai in the late 1960s, had his own brushes with Mr. Siritoitet, who objected to his research into the tribe’s traditional life.
“It was a time when much of the old heritage was destroyed,” Dr. Schefold said. “When they held rituals, the police would come and burn their traditional equipment — ‘the burning of the idols,’ as they considered it.”
The forced-conversion campaign deepened during the early years of the right-wing Suharto dictatorship, which worried that families, such as the Kapiks, who had not embraced a state-approved religion would be susceptible to Communist influence.
Only after Western tourists began paying visits to the forest people in the 1990s did the local government recognize the commercial advantages of allowing traditional Mentawai to live freely. By that point, an entire generation had been raised without the touchstones of traditional life.
Today, according to the Mentawai anthropologist Juniator Tulius, only around 2,000 Mentawai practice their traditional beliefs.
The tug between the old and new continues in the villages. In 2014, the Indonesian government established a single-payer universal health care system. Two years ago, a clinic that provides free health care to all was set up in Saibi Samukop, a village on the edge of the forest.
But a doctor there, Winda Anggriana, 26, said many residents had rejected her advice, in favor of consulting with shamans in the forest. “It’s deeply regrettable,” she said, listing patients with treatable conditions who had died during her nearly two years of working on the island.
A sharp divide has emerged between churches about how to handle the traditional Mentawai animist faith, in which many villagers still believe. In July, the Lutheran church in Mentawai celebrated the 100th anniversary of the first conversions of Mentawai people. During an interview, a Lutheran priest insisted there could be no synchronicity between Christianity and an animist faith.
Attempts to revive Mentawai tradition have begun, however haltingly. Indonesia began its transition toward democracy in 1998, and the youngest generation of Mentawai came of age during a less restrictive era. Activists have successfully pushed to add Mentawai culture to local elementary school curriculums. Today, Mentawai elders can worship and dress as they wish.
Still, many Mentawai are reeling from what they have lost over decades of government oppression. “My kids don’t know about their culture whatsoever,” said Mr. Sekaliou, the villager who will soon move back into the forest to tend to his parents.
Mr. Sekaliou said he was disappointed by his life in the village, saying he looked forward to staying with his parents during their twilight years. “Personally, I prefer living in the forest,” he said. “I’m happier there. I don’t have to stress about finding work every day.”
On a recent evening, as he watched his father return from feeding his pigs, he added: “The older generation is happier than we are.”
An earlier version of this article gave an incorrect date for Indonesia’s independence. The country gained its independence in 1945, not 1949.