When the American anthropologist Napoleon Chagnon first encountered members of the Amazon tribe he would spend his life studying, long strands of green snot were oozing from their nostrils. As soon as they saw him, a dozen men notched arrows in their bows and took aim. It was 1964, and Chagnon was starting his doctoral research on the Yanomamö Indians, a tribe living deep in the jungle near the border of Venezuela and Brazil. They were one of the last isolated tribes on the planet.

Many remote Yanomamö groups had never met an outsider, but these villagers were already familiar with a missionary named James Barker. Fortunately for Chagnon, Barker was his guide that day. They relaxed their bows when they saw the missionary.

From his graduate training at the University of Michigan’s anthropology department, Chagnon was primed to expect an egalitarian and peaceful group of natives to warmly welcome him. So he was surprised to learn why the Yanomamö had greeted him with drawn arrows: seven women had just been abducted by raiders from a neighboring village. Five were recovered in a bloody club fight that morning, and a counterattack might come at any moment. (The green snot was a temporary side effect of a snorted hallucinogen called ebene, which eased their mood of tense anticipation.)

After the shock of his first visit, Chagnon spent the next 25 years studying and living for long periods among the Yanomamö. He shot anacondas, killed poisonous snakes with a machete, and survived an attempt on his life. He also conducted thousands of hours of ethnographic research and constructed meticulous genealogies and life histories for several thousand Yanomamö.

His observations of widespread violence and his emphasis on Darwinian explanations shook some of the central orthodoxies of anthropology and generated a scandal that spilled into the popular media. It’s not hyperbole to call him the most controversial and famous anthropologist in America. His new book, Noble Savages: My Life Among Two Dangerous Tribes—The Yanomamö and the Anthropologists, is a memoir that offers a highly readable mixture of adventure, science, and scandal.

Chagnon quickly realized that living with a tribe in the Amazon is, to say the least, an enormous adjustment from America. The ubiquity of dirt and insects required such elaborate preparation routines that by the time he’d finished making breakfast it was time for lunch. Soon he was subsisting largely on sugared espresso, canned sardines, and peanut butter. A pulpy perimeter of raw sewage encircled each village, which made walking into the forest to find some privacy an ordeal.

He also endured linguistic hazing by the Yanomamö. They encouraged his malapropisms and were delighted when he confused similar words and proclaimed to a small crowd, “Yes, I’m horny!” After six months of diligently collecting residents’ names in one village, he traveled to a nearby village and casually mentioned some of the names. His hosts broke out laughing. He’d written an entire genealogy of salacious names: “Hairy Cunt” was married to “Long Dong,” their youngest son was “Asshole,” and so on. If Chagnon had studied only one village for fewer than six months, as many anthropologists do, the prank would never have been discovered.

After this incident, he developed a time-intensive method of verifying every fact he wanted to document. Before asking any subject about their ancestors, number of children, or causes of relatives’ deaths, he would first gauge their reliability by asking questions on topics of general Yanomamö knowledge, like geography or mythology. He would also fact-check every answer by questioning friends or relatives of the subject who weren’t aware of his initial interview. Often this meant traveling through the rainforest for several days to speak to relatives in distant villages.

A central claim of Chagnon’s new book is that larger units of political organization arose throughout human history when the need for protection against violent neighbors overcame the difficulties of living in bigger groups. Most Yanomamö villages were between one hundred and three hundred members, and he realized their size was constrained by two opposing pressures. Villages that were too small were vulnerable to raids by larger neighbors, whereas villages that were too large often dissolved because of internal squabbles. The choice, in other words, was between enduring frequent and devastating raids and learning to live with a higher percentage of non-relatives.

To a Darwinian anthropologist, it comes as no surprise that genetically related kin would form coalitions to wield power. And indeed, nearly all Yanomamö headmen have a greater number of male kin in their village than potential rivals do. But earlier anthropological models often downplayed natural selection and rejected the idea that hierarchies might be innate features of human society. Where these models assumed that individuals of the same age and gender would have roughly equal status in a village, Chagnon documented extensive kin-based hierarchies. He explained their presence in Darwinian terms: individuals who promote the survival of genetic kin are promoting the survival of their own genes. He also observed that power in Yanomamö villages was primarily defined by access to reproductive resources, not material ones. Powerful males had more wives and more offspring than less powerful males, and they were able to use their influence to provide close male relatives with wives. Power was both cause and effect of producing many genetically related kin in a village.

A more disturbing finding was the correlation he noticed between violence and reproductive success: Yanomamö men who had killed other men were statistically more likely to have more offspring than those who had not. After he published this result in the journal Science in 1988, Chagnon was accused of all sorts of things: the press paraphrased his article with splashy headlines like “Killers Have More Babies” and reduced his correlation to the implausible claim that there is a single “violence gene.” Some anthropologists alleged that he had fabricated his data, while others maintained that he himself was the cause of the violence he had documented. (This was because his presence supposedly sparked violent competition between villages for the Western goods he dispensed as payment for participating in genealogical surveys.)

Chagnon’s work suddenly became the principal battleground on which anthropology sought to define itself. Some anthropologists argued that the purpose of the field was to lobby for the rights of indigenous peoples and document their suffering at the hands of capitalist powers; since Chagnon’s work might promote a negative image of the Yanomamö, it was seen as a betrayal of the profession. This same contingent sparked recent debates within the American Anthropological Association over whether to strip the word “science” from its long-range plan.

Chagnon spends the final section of his book relating the academic and political scandals that swirled around his work in America and Brazil. He presents himself as the brave defender of scientific anthropology, unfairly attacked by politically correct and unscientific colleagues who couldn’t accept the stark truth of his findings. While Chagnon doesn’t give a terribly charitable account of his critics’ arguments in these conflicts, it’s clear that his work helped deflate a myth lingering in the minds of many. Those still clinging to some variant of Rousseau’s “Noble Savage” were appalled by Chagnon’s reports of frequent raiding, abduction, rape, and violence. A Yanomamö husband who even suspects his wife has been unfaithful might bash her in the head with firewood or shoot her in a nonlethal body part with an arrow, for instance.

If Chagnon and his critics were Yanomamö, they might settle their difference in a chest-pounding duel (which is basically what it sounds like). But implicit in the structure of his book is the barbed suggestion that beneath its veneer of civility, academic life is just a transfigured form of tribal warfare.