The war between Bisaasi-teri and Konabuma-teri started with an axe murder. The two Yanomamö villages, several days walk from each other in the forests around the unmapped headwaters of Orinoco river, had been moving towards an alliance when disease killed several children in Bisaasi-teri. The Yanomamö believe that disease is caused by evil spirits cast from other villages: when it falls upon them their shamans attempt to drive out the invading demons and to return them to the villages responsible. After the shamans of Bisaasi-teri concluded that the disease in their village had been cast from the purportedly friendly village of Konumba-teri, a respected visitor arrived from Konabuma-teri. He was greeted in the normal way: the men of the Bisaasi-teri came out with their weapons to yell at him intimidatingly until he had stood calmly for long enough to prove himself fearless. Then he was invited into the village — a single, circular, comunal roof covering family houses arranged around an open space — and given a gourd of soup to drink in front of the headman’s house. As he squatted on his haunches, drinking the soup, he was approached from behind by Mamikininiwä, who is described by the anthropologist Napoleon Chagnon as "a mature man of about forty, whose decisions few would challenge", and who carried an axe whose worn steel head had been traded over the course of years in from the coast. He smashed it into the visitor’s head without any warning, and the man died almost at once.

The story comes in the latest edition of Professor Chagnon’s classic work on the Yanomamö, subtitled until recentlyThe Fierce People, which goes on to trace a thirty-year pattern of migration, alliance, and emnity, that resulted from this murder in 1950: the Konumba-teri retaliated by arranging for mutual allies to hold a feast for the people of Bisaasi-teri and once their guests were comfortably immbiolised by the hammocks they were offered to rest in, attacked them with clubs and bowstaves, before pursuing the survivors with a flight of arrows. Around a dozen men were killed in this massacre. It’s difficult to be more precise because Chagnon learned of it only thirty years later and in any case, the Yanomamö counting system runs one, two, more-than-two.

The war within the American Anthropological Association probably started in 1994, with a shouting match between Professor Chagnon and Professor Terry Turner, of Cornell University, who called him "a sociopath" at a meeting arranged to reconcile Chagnon with the Salesian missionaries. It’s difficult to be more precise, because Chagnon and Turner had been enemies for years before then. But their equivalent of a murderous axe blow came this summer, with the release of an email, signed by Turner, and Professor Les Sponsel, of Hawaii University, in which they accused Chagnon of participation in "crimes beyond the imagination of Joseph Conrad, though not, perhaps, of Josef Mengele." In particular, he was supposed to have taken part in an experiment which started a deadly measles experiment among the Yanomamö in 1968, killing thousands and refusing medical treatment to those they had infected with a vaccine known to be potentially lethal. Both Turner and Sponsel are full professors, who have held high office in the AAA, "mature men, whose decisions few would question." The effect of their email was devastating. Had the charges been true, they would have finished Chagnon’s reputation as surely as an axe to the back of his head would have ended his life.

What is truly extraordinary about the story is that the charges set out in Turner and Sponsel’s email, are not only untrue; they could not possibly not be true, as reports of a full and thorough scientific investigation made plain in front of an enthralled crowd of four or five thousand anthropologists crammed into a ballroom at the Hilton Hotel in San Francisco last month — yet despite this, a sizeable minority of the profession clearly wish that one of their colleagues was guilty of genocide, and feel his moral guilt is established whatever the scientific and historical facts may be.

Napoleon Chagnon, the target of this animosity, is one of the most famous anthropologists alive. A large, bearded, weatherbeaten man, he lived and worked with the Yanomamö for a total of five years between 1964 and 1988 and his books and films about his time with them have become a set text in thousands of anthropology courses while at the same time provoking deep theoretical debates at the top of his profession and well outside it. He managed to combine dramatic human stories with a rigorous, but deeply controversial theory of the role of warfare and sexism in human nature which became one of the cornerstones of Evolutionary Psychology and all the modern Darwinism promoted by people such as Richard Dawkins, Dan Dennett and Steven Pinker. He argued that violence or the threat of violence shaped Yanomamö life in all sorts of ways and that the root of this violence was the competition between men for women.

But he had also made plenty of enemies. Some were professional. Chagnon’s explanation of Yanomamö violence was deeply controversial, both among people who understand it as a general theory of human nature (which it is meant to be), and among those who see it only as a particular explanation of Yanomamö culture. The Yanomamö are not in fact exceptionally violent by the standards of aboriginal people — which is to say that homicide is far more common among them than it is among better-armed, but more settled societies: it is something like eight times as high as New York’s, for example. Among the tribe, a quarter of all adult males die as a result of violence, according to Chagnon’s figures. But this is about in line with the rate for the !Kung bushmen of South Africa, and far below some figures recorded for other tribes in the Amazon basin, or in New Guinea and among some aborigines. But plenty of anthropologists who accept the facts of Yanomamö violence as recorded by Chagnon reject his interpretation of it: some believe they are fighting over food supplies; others that they fight for access to Westerners and Western artefacts, among them the machetes with which Chagnon and other antrhopologists trade for information.

Some of his enemies were personal. He is by all accounts a boisterous man. Moving among the Yanomamo, Chagnon had, or discovered in himself, the sort of personality that could thrive and impose itself on a brutal and treacherous political environment. For the first months of his fieldwork, while he was learning the language, the Yanomamö systematically lied to him. He needed to collect genealogies in order to trace the histories of the people he moved among, yet among the Yanomamö there is a tabu against using people’s names, and especially the names of the dead. He got around this difficulty by offering machetes to people who would talk to him: they squared their consciences by accepting the gifts but giving him false names for their fellow villagers. It took him five months to discover that the secret names for the chief’s family that he had so carefully collected actually translated as "long dick", "hairy cunt" and their daughter "fart breath". He overcame this obstacle with characteristic determination. It did not make him more trusting of the Yanomamö, and he later wrote: "It became indelibly clear to me shortly after I arrived that … I had to become like the Yanomamö to be able to get along with them on their terms: somewhat sly, aggressive, intimidating, and pushy.

"Had I failed to adjust in this fashion I would have lost six months of supplies to them in a single day … more importantly, had I failed to demonstrate that I could not be pushed around beyond a certain point, I would have been the subject of far more ridicule, theft, and practical jokes than the actual case." However effective this kind of behaviour may be among the Yanomamö it wins him little respect in the post-modern common room. He also lacks piety, both old-fashioned and modern. He is rude to and about missionaries, but when he discusses wife-beating among the Yanomamö he does not bother to tell us it is a wicked thing. He observes instead that it provides a low-cost way for a man to demonstrate his ferocity to other men. It is a common theme of his opponent that he is much more like the brutes he describes than the real Yanomamö are: they are not "the fierce people"; he is "the fierce anthropologist". Frank Salamone, a Catholic anthropologist who tried to broker a truce between Chagnon and the Salesian missionaries, says: "I believe the enmity is the result of Chagnon's harmful field methods, ‘fierce’ personality, and his tendency to lie. He has harmed the Yanomami by his false depiction of them and his failure to defend them in the press."

For the first ten years of his visits to the Orinoco jungles, until around 1975, Chagnon had enjoyed good relaitons with the Salesian Catholic missionaries who control access to most of the region. Indeed, the relationship was so good, he told me, that he was asked by one priest to arrange for the murder of another missionary who had gone off the rails and taken up with a Yanomamö concubine far up the river (he declined). Around then, the relationship started to unravel, and grew worse as Chagnon, and the Yanomamö, grew more famous. In 1987, he says, a German TV film with which he had co-operated described one Salesian as running a tourist trade to see the unspoilt savages. The missionaries were deeply offended, and managed to have him barred from the territory they controlled. When he returned, sponsored by the mistress of the Venezuelan president and by a controversial adventurer, dentist and sky-diver named Charles Brewer Carias, he quarelled once more with the Salesians.

They encourage the Yanomamö to move in from the highlands to the territory closer to the river, where they are more accessible to Western medecines and influences. Chagnon believes this makes the more vulnerable to diseases, too: "I got back into the field and re-censussed 25 villages I had worked with before. I began to see that this policy was having the effect of increasing the death rate in the resettled villages.

"On one of these trips a priest at Mavaca told me that they had attracted a village which I had found deep in the jungle years earlier to the river. He said they might not be there, becasue there was a week ago some jungle rumour that there was sickness there, but, he said, you know those Indian rumours. I went up there the same day and found that 25 people had died in the previous week and the goddamn missionaries had not even bothered to look.

"In general, the Yanomamö are constantly explaining epidemics in terms of the malevolent actions of anthropologist A, priest B or village X. And you don’t want to take to much notice. But this I saw with my own eyes."

His other charge, even more fiercely disputed, is that some Salesian missionaries have themselves exacerbate the fighting among the Yanomamö by arming them: "The missionaries have consistently used shotguns as a matter of policy to lure Indians away from the protestant missionaries. I found evidence of one raid deep in the interior, an unknown, remote village where the missionary village had gone to that village, killed a bunch of people stole a bunch of women, using shotguns. And there was no pre-existent enmity involved. I have evidence that the Indians from the mission village killed those Indians."

On his return, he made those charges public, and in an article for the New York Times added that he no longer dared return to the region because the Salesians had announced that they could not guarantee his safety there. He read this to mean that his enemies among the Yanomamö could feel free to kill him, knowing the missionaries would do nothing to stop them. At this point, in 1994, the public meeting at an AAA convention was held which ended in such raucous recriminations. "You’re goddamn right I want to respond" shouted Chagnon from the floor, when Turner promoted the cause of his own favourite Yanomamo spokesman.

There matters rested for a while. Chagnon could not return to the jungle; the Yanomamö themselves became poorer, more miserable, and more fashionable. Contact with the West is often fatal for South Americans, partly because they lack resistance to common diseases such as measles — which is a trivial childhood disease in Europe, but if it reaches an unexposed population is more infectious and more dangerous than the black death. It is expected to infect everyone who comes into contact with a sufferer and to kill at least half of those infected. Measles is only the most dramatic of the lethal diseases that contact with civilisation brings: tuberculosis leprosy and malaria can all be devastating in different tribes. Part of the vulnerability is genetic: it appears that South American Indians have immune systems that are uniquely vulnerable in some ways. Part is social: the normal response of an indigenous community to an epidemic is to flee, leaving the sick without nursing care. But a great deal is political. Dr Magdalena Hurtado, a Venezuelan anthropologist who has worked extensively with the Ache hunter-gatherers of Eastern Paraguay, says that government corruption and institutionalised racism all over South America mean that hardly anything is done to provide consistent, long-term medical care to newly contacted people, and often nothing is done in the short term either. She cites on Brazilian expedition to contact an unknown tribe, which consisted of 26 people, among them eight journalists from National Geographic magazine, and not a single doctor. It is believed that the entire tribe may have died as a result of that contact: they have since vanished from sight. Among those tribes whose fate is known, between a third and a half are expected to die within five years of first contact.

The Yanomamö are in a particularly unfortunate situation because their territory is believed to hold large gold reserves, and the impact of landless, desperate Brazilian gold miners has been terrible. In one notorious case in 1992, 12 Yanomamö women and children were massacred by gold miners. This led to a wave of fashionable outcry: they were the people whom Sting went to visit; but little practical help emerged. It was at the stage that a journalist named Patrick Tierney, who had earlier written a book claiming that human sacrifice survived among some Indian Andean tribes, spent a year among the gold miners. In 1995, he says he sent four or five chapters of his account to Professors Turner and Sponsel, who were then members of the ethics committee American Antrhropological Association. Sponsel, in Hawaii, did not meet him until this year. But Turner and he certainly met; and the book that Tierney proposed changed character sharply.

Sponsel says now "I believe he sent me one chapter or not many more on the gold mining. At that time I did what I do when any author or publisher sends me something to review. I remember one chapter called Napoleonic Wars. Tierney took that one chapter on the Napoleonic Wars and he basically turned that into an entire book. From my point of view he was going to expose gold-mining in the Amazon, – but that first book was basically dropped and I’m disappointed because I think the gold mining business is infinitely worse than Napoleon Chagnon or whatever."

Whatever the exact sequence of cause and effect (and Tierney could not, despite repeated efforts, be reached for an interview) Darkness in El Dorado, the book on Tierney’s adventures among the gold miners, which was to have been published by Viking in 1995, never appeared; instead, in the year 2000, W.W. Norton announced they were publishing Darkness in El Dorado, which was now a book about "How scientists and journalists devastated the Amazon" and in August Turner and Sponsel sent their email claiming that the book accused Chagnon and his former boss James Neel of genocide by measles. The effect was an immediate storm on the Internet, heightened because Norton refused to release copies of the book. The claims were repeated in this country by Survival International, who put out a press release, picked up by the Guardian and the BBC, though both organisations mentioned only Neel by name, since he died I February this year and can no longer sue. In November, the New Yorker published a curious excerpt from the book, with large holes in the argument where it appears that laywers and fact checkers had dined well; and in mid November, 5,000 members of the AAA gathered in San Francisco for their annual convention, or, in Yanomamö terms, five days of feasting when the ritual fighting could take place

When the Yanomamö fight in villages, they do not often try to kill each other. The men spend their afternoons snorting hallucinogenic powders which make them vomit, then drool green snot, and finally feel more cheerful. Then they’ll engage in trials of strength, where each man wants to outdo the others in enduring pain before he inflicts it back. At first, the contestants face each other, and then punch as hard as they can their opponent’s pectoral muscles. If that is not enough to solve the problem, they graduated to open-handed slaps on the kidney, delivered as hard as possible and again in turn. People can die from this. Then, as a last resort before the lethal violence, there is pole-fighting, where the contestants seize the five-metre whippy poles which hold up the house rooves, and take turns to smash them down as hard as possible on one another’s heads. The winner is the last man standing, but he will have taken some terrible blows in the process. One result of this contest is that the tonsured Yanomamö men are proud to have scalps so scarred by these tremendous blows that they look quilted.

The anthropologists eschew hallucinogens — though Chagnon, in the jungle, snorted ebene and drooled green snot with the best of them, and has been duly criticised for this by Tierney and Sponsel — but they too have their ritual trials of strength. They set up committees. In extremis, they do as Louise Lamphere, the president of the AAA, did this year, and hold a press conference to announce that they will set up a committee to decide whether they should set up a committee to investigate the allegations. "This book raises all sorts of ethical issues", she explained. "Is there anything in the AAA code of ethics that covers accusing your colleagues of behaving like Dr Mengele?" she was asked. "No, I don’t think so. I don’t think there’s anything that specific", she replied.

The equivalent of a full-scale pole fight among the anthropologists is a panel discussion. Just as with a pole fight, the contestants are judged by their ability to take blows, as well as to deal them out; and by this criterion Patrick Tierney has a stunning tolerance for pain. A gaunt, dark-eyed, dark-bearded man, he carried himself with the serenity of a martyr. The ballroom at the Hilton hotel, where this took place, was completely packed: about three thousand people sat on chairs, but they also stood in two rows at the back so that it was impossible to push between them, and sat on the carpeted three deep in front of the front row of chairs. Not everyone there had read the book: it’s probable that most hadn’t, even though the nearest bookshop was completely sold out. But it is certain that they had all read Turner and Sponsel’s email. Indeed, the two men were to speak the following evening.

At first, though, the showdown was simply between Tierney and the people who had tried to check his story, and who sat on the same dais. On the panel with him were a distinguished historian of science, Susan Lindee, who had access to Dr Neel’s papers and field notes from the expedition; Dr Magdalena Hurtado, a Venezuelan who had with her American husband done one of the most admired studies of a hunter-gatherer people, the Ache in Paraguay, Professor Bill Irons, a friend of Chagnon’s who had come along as his representative — Chagnon himself, retired and living in Michigan, announced through Irons that he was tired of the whole circus — and Yvonne Maldonado, an expert on infectious diseases and children.

There was also a token indigenous person, Nohely Pocaterra, from another Venezuelan tribe, whose interpreter was Jesus Cardoso, a former student and current enemy of Chagnon’s. She got by far the biggest cheer of the evening, for saying things like "You must be our friends or you must be our enemies. We thank you for your help to all the indigenous people of the world." But, since she spoke no English, it was less impressive than it might have been when she announced "I have come here to determine what happened, and if and of the allegations are proven true it is necessary to determine that they never happen again. You must guarantee that this never happens again to any people in the world." Because by that time, the panel speakers had shown, carefully and comprehensively, that nothing alleged about the measles epidemic had in fact happened at all. Admittedly, they had had help. The University of Michigan, where Neel had worked, had set twenty people to investigating the allegations against him. The University of California in Santa Barbara, where Chagnon had been a colleague of the evolutionary psychologists John Tooby and Leda Cosmides, had conducted an almost equally vigorous investigation.

By the end of the evening, the central, headline-grabbing allegations were in shreds: Turner and Sponsel had claimed in their email that the book proved

"Tierney presents convincing evidence that Neel and Chagnon, on their trip to the Yanomami in 1968, greatly exacerbated, and probably started, the epidemic of measles that killed "hundreds, perhaps thousands" (Tierney's language-the exact figure will never be known) of Yanomami ."

By the end of public sessions it had been shown that the epidemic was under way three months before the Neel/Chagnon expedition arrived: Thomas Headland, an anthropologist with the Sumner Institute of Linguistics (and no friend of Chagnon’s) read out a letter from an American missionary couple whose daughter, then aged 27 months, had unwittingly transmitted measles to a Yanomamö feast near the Brazilian border three months before the disease appeared on the upper Orinoco, a hundred and fifty miles away. The expedition’s field notes, retrieved by Susan Lindee, showed that they spent their first fortnight on a fire-fighting basis, innoculating all the Indians they could reach, and treating those who came down with the disease, even though this interfered with their research.

" The epidemic appears to have been caused, or at least worsened and more widely spread, by a campaign of vaccination carried out by the research team, which used a virulent vaccine (Edmonston B) that had been counter-indicated by medical experts for use on isolated populations with no prior exposure to measles (exactly the Yanomami situation). "

This, too, is quite untrue. The mortality rate among the villages where the vaccination had been carried out was far below what it would have been in an unvaccinated population. The idea that the Edmonston B vaccine was counter-indicated turns out to be due to the misquotation of sources in Tierney’s footnotes. Susan Lindee, a historian of science with full access to Neel’s papers proved at the meeting that the vaccine was in any case not chosen by Neel, but by the World Health Orgnisation, which wrote to eight different drug companies asking for their help: all produced at that time only the Edmonston virus. It has been administered 19m times in America alone and countelss times more around the world, to a huge variety of populations. It has never, not once, been observed to transmit measles to anyone.

"It was known to produce effects virtually indistinguishable from the disease of measles itself."

The source that Tierney gives for this is a doctor who was discussing the disease in Western children, where it is as mild as we recognise, and who went on immediately afterwards to say that in tropical countries, among populations where the disease is lethal, the situation was entirely different.

"Medical experts, when informed that Neel and his group used the vaccine in question on the Yanomami, typically refuse to believe it at first, then say that it is incredible that they could have done it, and are at a loss to explain why they would have chosen such an inappropriate and dangerous vaccine. "

The medical expert Tierney quoted denied saying any such thing. There is not a single medically qualified person who has come forward to say that that there is anything dangerous about the vaccine Neel and Chagnon used. This fact, like others inconvenient to him, Tierney simply ignored, with an expression, almost transfigured, of misunderstood martyrdom. The most he would concede at a press conference is that "the question of transmissibility is still up in the air": at this point Dr Yvonne Maldonado, the expert on infectious diseases and childhood immunisation on the panel, finally lost her cool and let him have it with both barrels: "you’re not a physician, not an epidemiologist and not even a scientist as far as I can tell.

"There is absolutely no evidence for transmissibility." By now she was almost shouting at the man two feet away from her. "There is no evidence! There could always be that one in a gazillion chance that it could happen somewhere in a parallel universe. The vaccine did not cause an epidemic. It did not cause deaths. Those people are not immunodeficient by any definition I know of. Lowered resistance has nothing to do with immune deficient. it speaks to the fact that they have not been exposed to that vaccine. Certainly we are currently vaccinating almost every child we can reach all round the world."

"There is no record that Neel sought any medical advice before applying the vaccine. He never informed the appropriate organs of the Venezuelan government that his group was planning to carry out a vaccination campaign, as he was legally required to do."

Susan Lindee produced records of the advice that Neel had sought, and received, from the Centre for Disease Control, which is the chief authority for infectious diseases in the USA, and where Dr Maldonado had acquired much of her expertise. It is clear that one Venezuelan institute was aware of his plans. Tierney, despite taking eleven years over a book which would allege that Dr Neel had planned a huge scientific experiment which would result in the death of thousands of innocent people, had never asked to see Neel’s papers, which are publicly accessible since his death. Lindee finished her speech by saying: "Tierney's unsupported insinuations could have a devastating impact -- historians and even journalists have ethical standards, and these too can be violated in ways that hurt vulnerable people."

"Once the measles epidemic took off, closely following the vaccinations with Edmonson B, the members of the research team refused to provide any medical assistance to the sick and dying Yanomami, on explicit orders from Neel .

He insisted to his colleagues that they were only there to observe and record the epidemic, and that they must stick strictly to their roles as scientists, not provide medical help ."

So far as anyone can tell, this is not only completely untrue, but was added by Turner and Sponsel to the horrendous allegations already in Tierney’s manuscript. It does not appear in the printed version, nor in the New Yorker excerpt. Their journals and films show clearly that the team not only vaccinated the uninfected Yanomamö , they treated those already sick with injections to bring their temperature down.

Through all this demolition, Tierney sat with the pale calm of a martyr, as if he were being reviled for the sake of the Yanomamö. When he finally came to microphone to answer his critics, he spoke with huge, aching silences between his phrases. "I feel that there have been many points raised tonight that I don't agree with. I never called the Edmonston B vaccine ‘virulent’. I never called it that. They are found in the famous Turner and Sponsel email: That email has coloured the reception of my text. I think you must read it first.

"I've seen the widows of Chagnon's guides who were bribed to break away from other villages. I have seen the people who were filmed watch those films and weep.

"John Tooby says that I had a bleeding heart. If you had seen the things that I have seen, I hope your hearts would be moved, and maybe they would be -- if you have a heart.

"Having checked all my footnotes, and having gone though my book. I want to ask, did they ever check Napoleon Chagnon's footnotes?"

Of course, none of this answered the points that the critics of his book had raised. But it did go some way to answering the question of why the audience was so willing to think ill of Chagnon. Throughout Tierney’s presentation, and his book, Chagnon appears as a kind of ogre-father, and the Yanomamö as helpless children at his mercy. Again and again, Chagnon’s critics maintain that the Yanomamö are not fierce at all: in fact they’re intrinsically harmless and he appears among them as a bully. Frank Salamone, quoting a Yanomamö enemy of Chagnon’s, put it as clearly as anyone: "Caesar Dimanawa said Chagnon is terrified of Yanomamö and terrified of Caesar. He is a wily kind of character and no more violent than my own relatives. It’s an interesting situation with Chagnon. he is afraid of them and they know this and take advantage of it. If you want to see violent people let him go to Nigeria where I did my fieldwork."

Les Sponsel held it against Chagnon that he went into the jungle armed with a huge knife and a stun-gun. It wasn’t, he said, ethical to work among people if you needed protection of that sort from them. At the open mike session, speaker after speaker returned to this theme, often prefacing their remarks with the confident assertion that they knew nothing about the Yanomamö but a great deal about professional ethics; and that it was surely the first principle of ethical anthropology to do no harm to the people you are studying. Since Chagnon’s activities have undoubtedly been part of the surge of Western interest and activity that has done much to damage the Yanomamö the moral case against him existed, in some sense, quite independent of the facts. But it seemed an extraordinary position for an anthropologist to take. Carried to extremes, it would lead to a complete ban on contact with any uncontacted people, since no amount of doing them good could outweigh a breach of the commandment to do them no harm. Still, it was clear that a sizeable minority of anthropologists think this is acceptable constraint for their colleagues to work under.

No one doubts that the situation of the Yanomamö and of the other indigenous peoples of South America is truly dreadful. "Their poverty is beyond poverty" says Frank Salamone. It is sometimes true that contact increases the horrendous infant mortality rates. What was odd was the belief to which Tierney seemed to appeal, that anthropologists could do something for the Yanomamö — could struggle on their sides — by ritually blaming themselves; better yet, by blaming other, unethical anthropologists for the evils of the world. It made about as much sense as the Yanomamö blaming measles on the wicked spirits sent from a neighbouring village, which is to say it probably did make people better about a situation they could do nothing to change.

Bill Irons, the Professor of Anthropology at Northwestern University who was Chagnon’s representative on the panel, was rather blunter. "People cultivate guilt for their own purposes. Pointing out how guilty everyone is has become part of the standard PC culture: somehow, slinging mud at everybody has become some kind of redeeming act.

"It is hardly fair to hold Napoleon Chagnon responsible for a Brazilian gold rush, or Venezuelan government corruption."

Professor Les Sponsel has a narrow, finch-like face and a smile of great charm. As one of the authors of the email that first attacked Chagnon and was later found to be a pack of lies, you might have expected him to have interesting views on ethics; and he does. His voice cracked with sincerity as he asked the meeting: "I have three questions for us to consider in the coming months. The first is, what have the Yanomamö contributed to us? The second is, what have we contributed to them, both for good and bad? The third is, how are professional ethics and human rights involved?

"This is not about science versus whatever: it is not about corruption in Venezuela, Brazil or the USA, This is about professional ethics."

Professional ethics are clearly quite different from the amateur ones that say things like "thou shalt not bear false witness", but when I pressed him on the question of whether he should not at the very least have checked these allegations of genocide against a colleague before passing them on, he grew quite heated. "I’m not a medical doctor. My role, ethically was to alert the AAA because of my concern with human rights. After that, the only role I had was to respond to questions when people asked me in a civil, polite manner. I and Terry Turner wrote that memo to the two top people in the organisation and sent copies to four other people in the committee on ethics. Whoever leaked it is the one who should be sanctioned or censured. It is most regrettable, most irresponsible, most appalling; and I am most infuriated that some person has basically stolen it … That people then steal it and gossip!"

"We were not making any allegations" he said. "May I repeat. We were not making any allegations. We were just summarising the allegations in Tierney. I am completely at peace with my conscience."

Chagnon, he said, "simply cannot face up to criticism constructively. He says that he is being attacked from professional jealousy, or by fools" By this stage, he was even more indignant than when he had been accused of amateur ethics. "Terry Turner and I have established our reputations. We’re not fools. There’s no reason for us to be professionally jealous and when he says that, he’s just not facing up to criticism constructively."

It is true that after the conference Professor Chagnon described Professor Turner and Professor Sponsel as "Absolute zeros."

But the thing that most impressed me about Professor Sponsel was his unshakeable conviction his own rightness: at least of Professor Chagnon’s wrongness. "I think there’s a lot of substance in Tierney’s book for the reasons I mentioned earlier. It’s not all false. There’s no way. One reason is that he has quotations and paraphrases and summaries by Chagnon himself which can be checked. And let me also say this. Let’s hypothetically say that the book is 100% a fabrication. Nevertheless what as that book done. It has stimulated a concern for the Yanomamö and for professional ethics within anthropology like never before.

"I think Patrick Tierney is a noble investigative journalist and I believe that people are innocent until they proved guilty."

And there matters, for the moment, rest. Tierney continues to go an American talk shows to plug his book. In parts of South America it already believed as a matter of fact that American scientists are using vaccination programs to conduct huge experiments (one of the anthropologists to speak in Tierney’s defence, a Ugandan, announced that the Ebola virus, too, had been introduced by scientists from the US and Europe). Chagnon broods over legal action. The war between Bisaasi-teri and Konabuma-teri continued for thirty years after the first axe murder; and when the old enemies made peace at a great feast, it was partly to form an alliance against a third village. It doesn’t look as if the war within the AAA will be any easier to end.

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