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.