“as Lynch pored over financial spreadsheets at work, he wondered: What if there really is a Z? What if the jungle had concealed such a place? Even today, the Brazilian government estimates that there are more than sixty Indian tribes that have never been contacted by outsiders. “These forests are . . . almost the only place on earth where indigenous people can survive in isolation from the rest of mankind,” John Hemming, the distinguished historian of Brazilian Indians and a former director of the Royal Geographical Society, wrote. Sydney Possuelo, who was in charge of the Brazilian department set up to protect Indian tribes, has said of these groups, “No one knows for sure who they are, where they are, how many they are, and what languages they speak.” In 2006, members of a nomadic tribe called Nukak-Makú emerged from the Amazon in Colombia and announced that they were ready to join the modern world, though they were unaware that Colombia was a country and asked if the planes overhead were on an invisible road.”