Other anthropologists rejected these assertions as exaggerated and even racist, saying they could do harm to the tribe by casting it in a bad light. Many argued that human behavior was best explained not by genetics and evolution but by the social and natural environments in which people live.

Still, Dr. Chagnon found a wide audience for his views. His ethnographic study “Yanomamö: The Fierce People” was published in 1968 and turned into a textbook that is widely described as the best-selling anthropology text ever.

In other books, and in interviews, he described his research in the Amazon jungle in swashbuckling terms, citing threatening snakes, jaguars and naked men armed with arrows no less sharp because their points were made of wood.

He visited the Yanomami year after year for months at a time, learning to communicate with them. Members of the tribe gave him the nickname Shaki , which Ms. Machak translated as “pesky bee” — a sobriquet he won, she said, because he was always pestering people with questions. His friends and colleagues called him Nap.

As his work received more and more attention, it drew increasing criticism from people ready to argue over practically anything about it, even the way he spelled the name of the tribe: Yanomamö.

The most serious attack came in 2000 , in the book “Darkness in El Dorado: How Scientists and Journalists Devastated the Amazon,” by Patrick Tierney, a journalist. Mr. Tierney accused Dr. Chagnon and a colleague of a wide range of misdeeds, including worsening a measles epidemic in the tribe to test their genetic theories and giving the Yanomami weapons that raised the level of tribal violence.