Villagers along the muddy banks of the Curanja River in the remote Peruvian Amazon are reporting frequent sightings and even raids by a mysterious, isolated tribe that lives deep in the rainforest. These isolated people rely on their deep knowledge of the ecosystem for food, medicines, and goods; now, pressures on the forest may be pushing them into the outside world. The events along the Curanja are the last, lingering echoes of the collision of cultures that began in 1492, in which an estimated 50 million to 100 million native people perished, and entire cultures vanished. Anthropologists and officials wonder if they can minimize the human toll of this final act. Lacking immunity to common pathogens and requiring large tracts of intact forest for their way of life, the isolated tribes are some of the world's most vulnerable people.