The Unconquered: In Search of the Amazon’s Last Uncontacted Tribes by Scott Wallace Crown, 494 pp., $26.00

Princeton graduate student Carol Mitchell looked up from her work and was transfixed by the sight of eleven naked men walking toward the thatch-roofed building in which she was compiling her field notes. Carol was alone that afternoon, since the other researchers at the station were off in the surrounding forest. Her startled indecision quickly turned to indignant impulse when some of the men began to gather up drying clothes from a nearby line. She rushed out of the building with a loud exclamation and snatched the clothes away from the now equally startled men. Returning briskly to the building, she slammed the door and deposited the rescued clothing on a table. There then ensued a standoff, Carol inside and the men outside, each staring at the other through the screen that served in lieu of a wall in the tropical climate. Thus did we come to know the Yaminahua or Yora people who lived upriver from us and who had terrorized their (and our) Matsigenka neighbors for at least a generation.

Carol didn’t know what to make of the delegation, but it was clear that they had come in peace, because they were not carrying weapons—bows and arrows. Multiple possibilities flashed through her adrenalin-fueled thoughts. It was clear from the hesitation on both sides that the station was not under attack, so Carol decided that hospitality would be the best policy. She came out of the building and, motioning for the men to follow, walked over to the dining hall next door. She then passed out cups and poured refresco (akin to Kool-Aid) for all to enjoy. The men, now gathered in the close quarters of the station’s dining facility, solemnly drank their portions.

With conversation impossible, silence reigned until the leader indicated that it was time to go. The men got up, but before they left, they gathered in a tight cluster only inches from Carol’s face and sang her a song. They then filed out of the building and continued their journey. We didn’t see any of them again for many months. These events took place in 1985 in the heart of Perú’s Manu National Park in the southwest Amazon at a rustic biological station where I have been conducting research with students and colleagues since 1973.

Neither we nor our Arawak-speaking Matsigenka neighbors could understand a word of what we later learned is a Panoan language. Thus the motives that inspired the Yora to come downriver where they had never previously ventured were unknown to us at the time. We later learned that an epidemic had swept through their community and that many had died, prompting survivors to seek help in the outside world. Some…