One of the first lessons you learn going into the field as an anthropologist, archaeologist or journalist is never to come back empty-handed. The cost of the expedition, the need to gratify sponsors, the urge to make a name, all turn up the pressure to get the story. So it’s easy to forget the second great lesson of fieldwork: beware of a story that’s just a little too good.

Thor Heyerdahl, who died in April at the age of 87, spent much of an active and sometimes inspiring life in the thrall of one good story. He believed that, long before Columbus, early ocean travelers—tall, fair-skinned, redheaded Vikings much like himself—spread human culture to the most remote corners of the earth. Academics scoffed, particularly at his idea that the islands of the mid-Pacific had been colonized by way of South America, rather than by Polynesians from the western Pacific. In 1947, Heyerdahl risked his life attempting to prove his point. He built a balsa-log raft, the Kon-Tiki, and in one of the great ocean adventures of the 20th century, he and his small crew made the harrowing 4,300-mile voyage from Peru to French Polynesia.

In the process, Heyerdahl established himself as an almost mythic hero. His best-selling book Kon-Tiki inspired a new generation of scholars—many of whom went on to systematically refute their hero’s great idea.

The trouble with a good story is that it has a way of distorting the facts: we see what we want to see and close our eyes to everything else. In the 1970s, scholars and filmmakers were so enraptured with the idea of peace-loving, Stone Age hunter-gatherers they failed to notice that the gentle Tasaday were a very modern Filipino hoax. In the harsher zeitgeist of more recent times, a hotly disputed book, Darkness in El Dorado, charges that anthropologist Napoleon Chagnon believed so firmly in the savagery of Venezuela’s Yanomami that he instigated the very bloodshed he went there to document. (Chagnon steadfastly denies the charge.)

A good story can be so compelling that teller and subject become entrapped together in its charms, and this was never more true than when Heyerdahl came swashbuckling onto Easter Island in 1955, determined to find hard evidence of South American origins.

He liked to be known to the islanders as Señor Kon-Tiki, and asked, among other things, for samples of old pottery, a technology known in South America but not in Polynesia. One enterprising islander promptly broke up a pot and buried the shards, a ruse Heyerdahl readily detected. “If there is a moral to all this,” another member of the expedition wrote later, “it is that archaeologists should be cautious about telling local, nonprofessionals what they would like to find.” Incautiously, Heyerdahl displayed a stuffed caiman from South America and the llama-like camel on a pack of cigarettes, to elicit the kinds of artifacts he sought.

His 1958 book, Aku-Aku, described just how brilliantly he succeeded. After discovering that the islanders had secret family caves full of “ancient” stone sculptures, Heyerdahl gained admission to them by invoking his own considerable spiritual aura, or aku-aku. By giving the islanders clothing, food and cigarettes, he persuaded them to hand over almost a thousand carvings, some of them redolent of South America: a penguin, llamas, a reed boat like the ones used on Lake Titicaca in Peru.

When I visited the islanders in 1992, they still clearly admired Señor Kon-Tiki, and they celebrated him as “good p.r. for Easter Island.” But they delighted in pointing out how selective and misleading he had been in the evidence he marshaled for his hypothesis.

One day I was talking with an island businessman in gold-rimmed glasses and a blue button-down shirt. “Thor knew I was a very good carver, and he came to see me,” he said. “He asked me to take out of my cave all the ancient objects that I had there, to sell to him. I told him I didn’t have anything, and he said, ‘I know exactly what you have. At the entrance to your cave, there is the head of a whale...’ And he started mentioning things that he insisted I had. I said I didn’t have them, and he said, ‘No, no, no! You have them and I’ll pay you for them.’ So I understood perfectly well that he was saying, ‘Carve them and I’ll pay you.’”

He thought about this for a moment, then added: “He was fooling the world. He was making his own spectacle....He was writing the book to make people say, ‘Ah!’ And it was good for the island in a certain way, because tourists came.”

The first time I heard this, I didn’t believe it: the islanders have a rich tradition of making up their own history, and they naturally wanted to seem like the shrewd ones in this relationship. But the implication that Aku-Aku was riddled with genial deceptions by Heyerdahl and the islanders, on one another and the world, came up over and over, with only minor variation.

One of the most interesting accounts came from a man whose secret cave was the source of 47 of the celebrated stone figures. In his 1975 book, The Art of Easter Island, Heyerdahl described at length how he determined their authenticity, concluding, “It was obvious to all of us that Pedro Pate could not have staged this cave. ...” Pate, now deceased, was a 73-year-old fisherman and carver at the time of my visit, and he laughed at the idea of authenticity. When he’d first brought a sack of carvings to Heyerdahl’s camp, he said Heyerdahl refused to look at them. The venue was wrong. “He said, ‘No, no, no, you take these things to the caves,’” where Heyerdahl could discover them.

At Pate’s cave, Heyerdahl wrote, he was particularly impressed with a carving of a two-masted reed boat, on which the dust lay a half-inch thick. He carried it out of the cave himself. To demonstrate that no modern islander could have produced such a masterpiece, Heyerdahl reported that one of the best carvers on the island had tried to create a replica; the result, he wrote, was clumsy and unconvincing.

I showed Pate a two-page photograph of the reed boat from Heyerdahl’s book, and he grinned. He’d carved the boat himself, he said. Dubious, I offered him $100 to carve such a boat now, 37 years later, and he accepted. When I visited him again, he was working in front of his house, with the half-formed sculpture propped up on a block of wood and his chisels, rasps and an adze laid out beneath him on a piece of corrugated cardboard.

A few days later, he presented me with the 18-inch-long reed boat he had carved. It was as good as the one in the book. I paid him, and as he wrapped the boat for me to take, he told me confidentially, like a shopkeeper suggesting a second pair of pants to go with a new suit, that he had actually carved two.

When I got the news, ten years later, that Heyerdahl had died, I retrieved that old carving from my yard. It’s broken into pieces now, and clotted with leaf litter and mud. I phoned an Easter Island archaeologist, William Ayres, who chairs the Pacific Island Studies program at the University of Oregon, and he confirmed that many of Heyerdahl’s cave carvings are now deemed modern. I leafed through my old notes from an interview with an islander who used to kid Heyerdahl in later years about the faked carvings. But Heyerdahl stuck by his story to the end. Once, at a conference, a colleague asked him how he could persist with the South American hypothesis when his own archaeologists had produced overwhelming evidence that the Easter Island culture had, in fact, come from Polynesia. Heyerdahl looked down at him like a giant crane peering down on a small worm, and he said, ‘‘Well, I have my audience.”

An audience is what everyone who works in the field ultimately wants: a chance to climb up out of the dust and make the world say, “Ah!” But at what cost? Turning over Pedro Pate’s sculpture and studying it under the light at my desk, it seemed to me that what I held in my hand was that titillating and very dangerous thing: a good story.          

As a child, author Richard Conniff regarded Thor Heyerdahl as a hero.