What were our early ancestors really like as they accomplished the transition from hunter-gathering bands to more complex settled societies? The anthropologist Napoleon A. Chagnon may have come closest to the answer in his 35-year study of a remarkable population, the Yanomamö of Venezuela and Brazil.
His new book, "Noble Savages," has three themes. First, it is a beautifully written adventure story of how Dr. Chagnon learned to survive in an entirely alien culture and environment, among villages locked in perpetual warfare and jaguars that would stalk his tracks through the jungle. Second, it describes the author's gradual piecing together of how Yanomamö society actually works, a matter of great relevance to recent human evolution. Third, it recounts his travails at the hands of the American Anthropological Association.
Most tribes studied by anthropologists have lost much of their culture and structure under Western influences. In the 1960s, when Dr. Chagnon first visited them, the Yanomamö were probably as close as could be to people living in a state of nature. Their warfare had not been suppressed by colonial powers. They had been isolated for so long, even from other tribes in the Amazon, that their language bears little or no relationship to any other. Consisting of some 25,000 people, living in 250 villages, the Yanomamö cultivated plantains, hunted wild animals and raided one another incessantly.
Trained as an engineer before taking up anthropology, Dr. Chagnon was interested in the mechanics of how the Yanomamö worked. He perceived that kinship was the glue that held societies together, so he started to construct an elaborate genealogy of the Yanomamö (often spelled Yanomani.)
The genealogy took many years, in part because of the Yanomamö taboo on mentioning the names of the dead. When completed, it held the key to unlocking many important features of Yanomamö society. One of Dr. Chagnon's discoveries was that warriors who had killed a man in battle sired three times more children than men who had not killed.
His report, published in Science in 1988, set off a storm among anthropologists who believed that peace, not war, was the natural state of human existence. Dr. Chagnon's descriptions of Yanomamö warfare had been bad enough; now he seemed to be saying that aggression was rewarded and could be inherited.
A repeated theme in his book is the clash between his empirical findings and the ideology of his fellow anthropologists. The general bias in anthropological theory draws heavily from Marxism, Dr. Chagnon writes. His colleagues insisted that the Yanomamö were fighting over material possessions, whereas Dr. Chagnon believed the fights were about something much more basic -- access to nubile young women.
In his view, evolution and sociobiology, not Marxist theory, held the best promise of understanding human societies. In this light, he writes, it made perfect sense that the struggle among the Yanomamö, and probably among all human societies at such a stage in their history, was for reproductive advantage.
Men form coalitions to gain access to women. Because some men will be able to have many wives, others must share a wife or go without, creating a great scarcity of women. This is why Yanomamö villages constantly raid one another.
The raiding over women creates a more complex problem, that of maintaining the social cohesion required to support warfare. A major cause of a village's splitting up is fights over women. But a smaller village is less able to defend itself against larger neighbors. The most efficient strategy to keep a village both large and cohesive through kinship bonds is for two male lineage groups to exchange cousins in marriage. Dr. Chagnon found that this is indeed the general system practiced by the Yanomamö.
After overtaxing one of his informants, the shaman Dedeheiwä, about the reason for a succession of village fissions into smaller hostile groups, Dr. Chagnon found himself rebuked with the outburst, "Don't ask such stupid questions! Women! Women! Women! Women! Women!"
During his years of working among the Yanomamö, Dr. Chagnon fell into cross purposes with the Salesians, the Catholic missionary group that was the major Western influence in the Yanomamö region. Instead of traveling by canoe and foot to the remote Yanomamö villages, the Salesians preferred to induce the Yanomami to settle near their mission sites, even though it exposed them to Western diseases to which they had little or no immunity, Dr. Chagnon writes. He also objected to the Salesians' offering the Yanomamö guns, which tribe members used to kill one another as well as for hunting.
The Salesians and Dr. Chagnon's academic enemies saw the chance to join forces against him when the writer Patrick Tierney published a book, "Darkness in El Dorado" (2000), accusing Dr. Chagnon and the well-known medical geneticist James V. Neel of having deliberately caused a measles epidemic among the Yanomamö in 1968.
On the basis of these accusations, two of Dr. Chagnon's academic critics denounced him to the American Anthropological Association, comparing him with the Nazi physician Josef Mengele. The association appointed a committee that, though it cleared Dr. Chagnon of the measles charge, was nevertheless hostile, accusing him of going against the Yanomamös' interests.
In 2005, the association's members voted by a 2-to-1 margin to rescind acceptance of the committee's report. But the damage was done. Dr. Chagnon's opponents in Brazil were able to block further research trips. His final years of research on the Yanomamö were disrupted.
In 2010 the A.A.A. voted to strip the word "science" from its long-range mission plan and focus instead on "public understanding." Its distaste for science and its attack on Dr. Chagnon are now an indelible part of its record.
Dr. Chagnon's legacy, on the other hand, is that he was able to gain a deep insight into the last remaining tribe living in a state of nature. "Noble Savages" is a remarkable testament to an engineer's 35-year effort to unravel the complex working of an untouched human society.
This article originally appeared in The New York Times.