As Martina Canchi Nate runs through the Bolivian jungle, red butterflies fluttering around her, we have to ask her to stop – our team can’t keep up.

According to her ID, she is 84 years old, but within ten minutes she digs up three yucca trees to separate the tubers from the roots and cuts down a banana tree with just two blows of a knife.

She loads a large bundle of fruit onto her back and sets off home from her chaco – the piece of land where she grows cassava, corn, plantains and rice.

Martina is one of 16,000 Tsimanes (pronounced “chee-mai-na”) – a semi-nomadic indigenous community living deep in the Amazon rainforest, 600 km north of Bolivia’s largest city, La Paz.

Their vitality is not unusual for Tsimanes their age. Scientists have concluded that the group has the healthiest arteries ever studied and that their brains age more slowly than those of people in North America, Europe and elsewhere.

The Tsimane are a rarity. They are one of the last peoples on Earth who subsist exclusively on hunting, foraging and agriculture. The group is also large enough to provide a sizable scientific sample, and researchers led by anthropologist Hillard Kaplan of the University of New Mexico have studied them for two decades.

Tsimane are constantly active – they hunt animals, grow food and weave roofs.

They spend less than 10% of daytime hours sedentary, compared to 54% in industrial populations. An average hunt, for example, lasts more than eight hours and covers 18 km.

They live on the Maniqui River, about 100 kilometers by boat from the nearest town, and have little access to processed food, alcohol and cigarettes.

The researchers found that only 14 percent of the calories they consume come from fat, compared to 34 percent in the U.S. Their foods are high in fiber, and 72 percent of their calories come from carbohydrates, compared to 52 percent in the U.S.

Proteins come from the animals they hunt, such as birds, monkeys and fish. Cooking traditionally does not involve frying.

The initial work of Prof. Kaplan and his colleague Michael Gurven from the University of California in Santa Barbara was anthropological in nature. But they noticed that the older Tsimane showed no signs of typical age-related diseases such as high blood pressure, diabetes or heart problems.

Then a study published in 2013 caught their attention. A team led by US cardiologist Randall C. Thompson used computer tomography to examine 137 mummies from the ancient Egyptian, Inca and Unangan cultures.

As people age, fats, cholesterol and other substances can thicken or harden arteries, causing atherosclerosis. They found signs of this in 47 of the mummies, challenging the idea that it is caused by modern lifestyles.

The two research teams joined forces and conducted CT scans on 705 Tsimane people over the age of 40 to look for coronary artery calcification (CAC), a sign of blocked blood vessels and the risk of heart attack.

Their study, first published in Tthe Lancet in 2017found that 65% of Tsimanes over 75 did not have CAC. In comparison, most Americans of that age (80%) have signs of it.

As Kaplan puts it, “The arteries of a 75-year-old Tsimane are more like the arteries of a 50-year-old American.”

A second phase, published in 2023 A study published in the journal Proceedings of the National Academy of Science found that older Tsimane people had up to 70 percent less brain atrophy than people of the same age in industrialized countries such as the United Kingdom, Japan and the United States.

“We found zero cases of Alzheimer’s in the entire adult population – that’s remarkable,” Bolivian doctor Daniel Eid Rodríguez, the researchers’ medical coordinator, tells us.

Determining the age of the Tsimane is not an exact science, however. Some have difficulty counting because they have not learned the number system well. They told us that they rely on records from Christian missions in the area or on how long they have known each other. The scientists base their calculations on the ages of a person’s children.

According to her records, Hilda is 81, but she says her family recently slaughtered a pig to celebrate her “100th birthday or something like that.”

Juan, who says he is 78, takes us hunting. His hair is dark, his eyes lively and his hands muscular and strong. We watch him stalk a small taitetú – a hairy wild boar – which manages to sneak through the foliage and escape.

He admits that he is feeling his age: “The hardest thing now is my body. I don’t go far anymore… it will be two days at the most.”

Martina agrees. Tsimane women are known for weaving roofs out of jatata, a plant that grows deep in the jungle. To find it, Martina has to walk three hours there and three hours back, carrying the branches on her back.

“I do it once or twice a month, although it’s harder now,” she says.

However, many Tsimanes never reach old age. At the start of the study, their average life expectancy was just under 45 years – it has now risen to 50 years.

At the clinic where the scans take place, Dr. Eid asks the elderly lady about her family as they prepare for the examination.

One woman counts on her fingers and says sadly that she had six children, five of whom died. Another says she had twelve, four of whom died. Another says she has nine children still alive, but three more have died.

“The people who reach the age of 80 are those who survived a childhood full of disease and infection,” says Dr. Eid.

The researchers believe that all Tsimanes suffered from some form of parasitic or worm infection at some point in their lives. They also found high levels of pathogens and inflammation, suggesting that the Tsimanes’ bodies were constantly fighting infection.

This has led them to wonder whether these early infections could be another factor – in addition to diet and exercise – responsible for the health status of the older Tsimanes.

However, the community’s lifestyle is changing.

Juan says he hasn’t been able to hunt a large enough animal for months. A series of wildfires destroyed nearly two million hectares of jungle and forest in late 2023.

“The fire drove the animals away,” he says.

He has now started raising livestock and shows us four cattle that he hopes will provide the family with protein throughout the year.

According to Dr. Eid, the use of outboard motor boats – known as peque-peque – is also bringing about change. They make markets easier to reach and give the Tsimane access to foodstuffs such as sugar, flour and oil.

And he points out that as a result they row less than before – “one of the most physically demanding activities”.

Twenty years ago, there were hardly any cases of diabetes. Now they are becoming more common and cholesterol levels are also rising in the younger population, the researchers found.

“Every small change in their habits ultimately affects these health indices,” says Dr. Eid.

And the researchers themselves have achieved a lot over the course of their 20 years of commitment: They have given the Tsimanes better access to health care, from cataract surgery to treatment for broken bones and snake bites.

But for Hilda, old age is not something to be taken too seriously. “I’m not afraid of dying,” she tells us, laughing, “because they’ll bury me and I’ll stay there… very quietly.”