An international team of anthropologists working in Ecuador conducted the study.
“In 1988, Napoleon Chagnon published evidence that among the famously warlike Yanomamo of Venezuela, men who had participated in a homicide had significantly more wives and children than their less warlike brethren. Our research among the Waorani indicates that more aggressive warriors have lower indices of reproductive success than less warlike men,” said Stephen Beckerman, associate professor of anthropology, Penn State.
The Waorani are rainforest manioc horticulturalists and foragers, known for warfare and murder. They practiced their violence on each other as well as on outsiders. Eventually, over a period of 14 years, the missionaries pacified all the sections of the Waorani population, bringing an end to the aggressive warfare and raiding.
“In light of the documented abundance of wild resources, resource limitation cannot be considered the cause of warfare among the Waorani,” said Beckerman.
The Waorani Life History Project looked at how a man’s participation in raiding correlates with his survivorship and that of his wives, the number of his wives and the number of children he produced and their survivorship.
For the study, the researchers interviewed men in 23 settlements, focussing mainly on any man old enough to have experienced warfare before the pacification that could be found and who agreed to the interview.
They collected Waorani men’s genealogies, reproductive history, narrative personal life history and warfare history. The raiding database contained 95 men.
“Our sample of warriors includes both living and dead men. We ranked aggression by the number of raids they participated in. Our analysis is free of the problem caused by the inherent correlation of the warrior’s age with both participation in raids and reproductive success,” said Beckerman.
The researchers found that more aggressive men do not acquire more wives than milder men and they do not have more children as well as their wives and children do not survive longer.
In fact, warlike men have fewer children who survive to reproductive age.
The findings have been published online in the Proceedings of the National Academy of Science.