During World War II, the tiny island of Tanna in the South Pacific became one of many outposts that American troops temporarily occupied. The residents of Tanna, previously sheltered from the developed world, were exposed to things like radios, packaged foods, cigarette lighters, and Jeeps. They never forgot the mysterious luxury goods that the G.I.’s brought with them.

After the troops moved away, some of these remote people groups developed “cargo cults,” religions based around the worship of a god who would one d…