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.