India, March 21 -- For millions of years, we moved through the world and left almost no trace at all. It's what makes the study of early humans so challenging.

Incredibly, there are still humans who live like this.

In 2021, a team of government researchers in Brazil found traces of one such uncontacted tribe: signs of campsites and rough-hewn ceramic pots and baskets, deep in the Mamoria Grande region of the Amazon rainforest.

It was known that a tribe lived here (the Amazon is home to most of the world's remaining 100-odd uncontacted tribes). But this was the first evidence officially recorded. Last December, FUNAI, the indigenous affairs agency of the Brazil government, acted on that information to pass new norms that prevent further...