Tierney never claimed, then, that Chagnon was the sole cause of the violence he recorded. Tierney's research—and that of others, such as Brian Ferguson—does show that some of Chagnon's actions had the effect of promoting conflicts that he then attributed to the ferocity of the people he was studying. (Tooby writes, irrelevantly, that other pre-state societies have higher rates of violence, but he never refutes Tierney's argument that Chagnon's account of warfare among the Yanomamö was exaggerated.) Tierney pointed out that missionaries gave machetes to the Yanomamö, beginning in the '50s, and that it was a cause of warfare. But Chagnon's machete trade was distinctive, Tierney showed, and distinctly destabilizing. Chagnon provided machetes in exchange for the names of dead relatives, a violation of tribal taboos, and in doing so, he contributed to discord among the Yanomamö. Chagnon also gave some Yanomamö villages a large number of machetes at once in exchange for their participation in his research projects. In one case, Tierney reported, he created an alliance between two villages which resulted in a raid on a third village and a death. In another case, which Chagnon describes in his book Yanomami: The Fierce People, the act of choosing one village over another for collecting blood samples in exchange for machetes resulted in conflict. According to one tribal leader Tierney spoke to, Chagnon promised machetes to those who would take part in an alliance that Chagnon created in order to make the film The Feast.
