A decade ago the American journalist Patrick Tierney published an incendiary book called Darkness in El Dorado. Tierney had spent more than ten years investigating the work of the anthropologist Napoleon Chagnon, and of Chagnon’s mentor, the geneticist James Neel. He accused Chagnon, among other things, of scientific fraud, sexual abuse, political corruption and, most sensationally, of genocide.

Chagnon was one of the most distinguished anthropologists of his generation, who had made his name as a pioneer of sociobiology and of evolutionary accounts of violence. He had spent a lifetime studying the Yanomamo, an Amazonian tribe that live on borderlands of Brazil and Venezuela. Chagnon presented the Yanomamo as a fierce, primitive tribe, given to murderous violence, whose mores opened the window onto the human past (‘our contemporary ancestors’ as he described them). Most controversially, he linked Yanomami violence to genetic success. The more people a man had killed, Chagnon claimed, the more wives and children he was likely to have. Violence, in his view, enhanced Yanomami men’s reproductive success.

An academic war erupted in the early 1990s as other Amazonian specialists questioned Chagnon’s methods and data. Many questioned his politics, too. The anthropologist Leslie Sponsel, for instance, lambasted the ‘Darwinian emphasis on violence and competition’, arguing instead for an ‘anthropology of peace’.

Darkness in El Dorado provided the material that Chagnon’s political critics needed. Tierney accused Chagnon not simply of poor methodology but, sensationally, of mass murder too. According to Tierney, Chagnon and Neel had deliberately infected the Yanomamo with measles, creating an epidemic that wiped out hundreds, perhaps even thousands, of people as part of a grotesque experiment to test the impact of natural selection on primitive groups. It was, in Tierney’s words, ‘science in the service of ethnocide’.

The trouble is, as a series of investigations by anthropologists, historians and others have revealed, there is barely a shred of evidence for Tierney’s monstrous claims. Indeed, he seems to have made up much of his ‘data’. The latest study to rip apart Tierney’s book is by historian and bioethicist Alice Dreger.  Dreger’s paper, which expands on a presentation she gave to the 2009 American Anthropological Association conference, reveals, among other things, that a dossier about Chagnon’s misdeeds that Tierney claimed was circulated by indigenous activists, and which forms the centerpiece of his book, was in fact written by Tierney himself. After having written it, he persuaded a Brazilian-born scholar, Leda Martins, not only to translate the dossier into Portuguese but to pretend that it was her own work.

There is a tabloidy quality to Dreger’s paper (including such ad hominem attacks as the claim that Tierney ‘comes across as a man trying to walk in the footsteps of Jesus’) that is irritating. Nevertheless it provides a devastating critique not just of Tierney’s work but even more so of the American Anthropological Association.  For the really interesting questions are less about Tierney’s fabrications than about why so many anthropologists, including the leadership of the AAA, should be so keen to believe them. Despite the evidence that Tierney made up much of his data, many anthropologists have continued to take them seriously. The AAA set up a special taskforce to investigate Tierney’s claims which concluded that ‘Darkness in El Dorado has served anthropology well’.

What is striking is that, as Dreger points out, those who came to that conclusion were in no doubt as to reality of Tierney’s book. In 2002 Jane Hill, a former president of the AAA, and chair of the task force, sent an extraordinary email to the anthropologist and primatologist Sarah Hrdy, who had objected to the refusal of the task force to face up to the facts:

Burn this message. The book is just a piece of sleaze, that’s all there is to it (some cosmetic language will be used in the report, but we all agree on that). But I think the AAA had to do something because I really think that the future of work by anthropologists with indigenous peoples in Latin America—with a high potential to do good—was put seriously at risk by its accusations, and silence on the part of the AAA would have been interpreted as either assent or cowardice. Whether we’re doing the right thing will have to be judged by posterity.

In other words hang the facts. It was politically necessary to skewer Chagnon to protect ‘the future of work by anthropologists with indigenous peoples’. The fact that the accusations amounted to a ‘piece of sleaze’ was irrelevant. This gets to the heart of the Tierney controversy. For the assault on Chagnon’s reputation was part of a much more profound debate about the very nature of anthropology. Should anthropology be seen as a science? Or as a form of advocacy?

For Tierney and his supporters anthropology is less a scientific discipline than a political mission, the aim of which is to defend the dispossessed. Anthropologists cannot simply be observers, as traditional scientific objectivity requires, but must actively take sides in any political struggle involving the peoples they are studying. And in such a struggle the norms of scientific objectivity must be subordinate to the political aims.

Last December the AAA decided that its mission was no longer ‘to advance anthropology as the science that studies humankind in all its aspects’, but to ‘to advance public understanding of humankind in all its aspects.’ It might seem a subtle shift. But it was a shift in keeping with its whole attitude to the Tierney affair: that what mattered was less scientific truth but ideological correctness (or ‘public understanding’ put it in more politically acceptable terms).

The irony is that there are genuine questions to be raised about Chagnon’s methods. For example, in his book Yanomami Warfare: A Political History, a fellow Yanomamo scholar, Brian Ferguson, claimed that Chagnon’s methods had distorted his data, changing the political balance between different Yanomamo groups by selectively providing steel goods and weapons to certain groups, and by rewarding displays of aggression with machetes and other highly prized tools. Others have questioned Chagnon’s statistics. And I, like many, have been critical of many of the methods and assumptions of sociobiology. But whatever one thinks about Chagnon’s work, or about sociobiology, there can be no critique of it if we dismiss the possibility of a scientific study of humankind. Advocacy, as Dreger points out,  ‘is not scholarship’:

The former is specifically concerned with advancing human rights, the latter with the production of knowledge. To insist that scholars of a particular discipline adhere to and even advance preordained social politics looks to me frighteningly like the situation Galileo found himself in.

Nor, as Dreger concludes, is it just scholarship that suffers when evidence gets fabricated and politically inconvenient facts dismissed. The possibility of social justice does too:

I understand that those who were involved in this controversy may have had good intentions. Many sought justice. But justice that is meted out according to politics and not according to facts is the justice of the Middle Ages. If justice is not based on the facts, if principles of justice are not applied universally, there is no real justice. Forms of ‘scholarship’ that deny evidence, that deny truth, that deny the importance of facts – even if performed in the name of good – are dangerous not only to science and to ethics, but to democracy. And so they are dangerous ultimately to humankind.