The e-mail is quoted in a paper by Alice Dreger that appeared in the journal Human Nature in 2011. Dreger, a professor of bioethics at Northwestern, was writing a book about scientific controversies in the Internet age, when she learned about the scandal in anthropology. She researched the case for a year, conducting 40 interviews, and by the time she published her paper, she considered Chagnon a friend, a fact reflected in her sometimes zealous tone. Among other things, she discovered that Tierney helped prepare a dossier critical of Chagnon, which he attributed to Leda Martins, a Brazilian anthropologist: “Leda’s dossier was an important resource for my research.” (Martins says that she translated the dossier into Portuguese.) But Dreger reserves her most withering remarks for the A.A.A. She told me, “All these people knew that Tierney’s book was a house of cards but proceeded anyway because they needed a ritualistic cleansing.”

In fairness, Tierney seems to have gotten some things right. The task force called his account of Chagnon’s Fundafaci episode one of the “better supported allegations.” And many have vouched for Tierney’s description of Jacques Lizot, Chagnon’s French rival, ensconced in the jungle with an entourage of Yanomami boys, whom he plied with trade goods in exchange for sex. (Lizot has said that the sex was between consenting adults.)

Yet it’s possible to imagine how a discipline seeking to expiate its sins could have overreached in Chagnon’s case. He was prominent and controversial, a sociobiologist who declined to put activism on a par with research. On the rare occasions that he adopted the mantle of advocate, the gesture typically backfired, as when he told a Brazilian magazine: “The real Indians get dirty, smell bad, use drugs, belch after they eat, covet and sometimes steal each other’s women, fornicate and make war. They are normal human beings. This is reason enough for them to deserve care and attention.” His critics, appalled by the first sentence, typically ignored the rest.

In this charged atmosphere, Tierney was to play a vital role: that of the impartial journalist who would give the discipline’s verdict on Chagnon the stamp of objectivity. Yet as Tierney himself admitted, he was not impartial. “I gradually changed from being an observer to being an advocate,” he wrote. “It was a completely inverted world, where traditional, objective journalism was no longer an option for me.” Was objectivity possible for anyone?

In 2005, the A.A.A.’s members agreed to rescind the task-force report, by a vote of 846 to 338. Daniel Gross called Chagnon to give him the news. “I saved that phone message for years,” Chagnon told me. “That was the point at which my emotional stability began to ascend.” Last spring, he was elected to the National Academy of Sciences — a prestigious honor that he took as vindication. “A lot of anthropologists have red faces from the extent to which they advocated in support of the accusations against me,” he said.

Not every critic has conceded. “The charges have not all been disproven by any means,” Leslie Sponsel pointed out. Leda Martins, who teaches at Pitzer College in Los Angeles, was more circumspect. “The controversy is so big, and the devil is all in the details,” she said. “Unless you know where Chagnon was, in what village, and what he was doing — unless you know everything — it’s really hard to talk about it.” I told her I thought that Tierney was sure he’d found another Kurtz, another “Heart of Darkness.” “Patrick and Chagnon have some similar characteristics,” Martins replied. “How ironic is it that Patrick got carried away in the same way that Chagnon got carried away?”

By now, at least a few Yanomami have read both “The Fierce People” and “Darkness in El Dorado,” and many more have been told about their contents by people with varied agendas. During an interview with a member of the A.A.A.’s task force, Davi Kopenawa, a Brazilian Yanomami leader, was invited to pose some questions of his own. “I want to ask you about these American anthropologists,” he said. “Why are they fighting among themselves? Is it because of this book?”

The interviewer answered in the affirmative, and Kopenawa went on: “So, Chagnon made money using the name of the Yanomami. He sold his book. Lizot, too. I want to know how much they are making each month. How much does any anthropologist earn? And how much is Patrick making? Patrick must be happy. This is a lot of money. They may be fighting, but they are happy. They fight, and this makes them happy.”