I want to pass along a story from Slate's Monte Reel, about a modern-day Ishi in remote Brazil: "The most isolated man on the planet."
Eventually, the agents found the man. He was unclothed, appeared to be in his mid-30s (he's now in his late 40s, give or take a few years), and always armed with a bow-and-arrow. Their encounters fell into a well-worn pattern: tense standoffs, ending in frustration or tragedy. On one occasion, the Indian delivered a clear message to one agent who pushed the attempts at contact too far: an arrow to the chest.
It's hard to tell how sensationalized the story is, but the reality is that there are many small groups of people who survive on the run from squatters intent on driving them from their land.