Chagnon's ethnography, Yanomamö: The Fierce People was published in 1968 and later published in more than five editions and is commonly used as a text in university-level introductory anthropology classes, making it the all-time bestselling anthropological text.

As Chagnon described it, Yanomamö society produced fierceness, because that behavior furthered male reproductive success. According to Chagnon, the success of men in violent interaction and even killing, was directly related to how many wives and childern they had. At the level of the villages, the war-like populations expanded at the expense of their neighbors. Chagnon's positing of a link between reproductive success and violence cast doubt on the sociocultural perspective that cultures are constructed from human experience. An enduring controversy over Chagnons' work has been described as a microcosm of the conflict between biological and sociocultural anthropology. [excerpted from the Wikipedia article on Napoleon Chagnon]