A new study from Harvard University shows that there may be a biological benefit to violent conflict.
The study found that among members of an East African herding tribe, those who engaged in violent raids on neighboring tribes had more wives, leading to the opportunity to have more children.
“The currency of evolution is reproductive success,” said Luke Glowacki, a doctoral student at the university. “By having more wives you can have more children. What we found was that, over the course of their lives, those who took part in more raids had more children.”
The benefit actually comes from an increased access to livestock, which is then used to arrange marriages, he said, noting it’s tied to the tribe’s culture.
“The cultural mechanism is mediated by the elders who control virtually all aspects of the society,” he said.
“After a raid young men give any livestock they capture to the elders and the raider cannot use them at that point even if he wants to get married. Later in life, as the raider gets older he can gain access to them, so there’s a lag in receiving benefits from participating in a raid.”
To examine the connection between violence and a possible biological benefit, Glowacki lived with the Nyangatom, a group of nomadic herders in a region of southwest Ethiopia and South Sudan, for more than a year. During that time, he observed virtually every part of day-to-day village life, from digging water holes to migrations to the raids.
The raids, typically carried out by men between 20 and 40 years old armed with weapons like AK-47 rifles, sometimes resulted in serious injuries and deaths, the researcher noted.
Those who take part in the raids, however, must turn over any livestock they obtain to village elders, who use them to obtain wives for themselves. It may not be until years later that elders agree to provide a raider with the cows necessary to obtain their first wife or subsequent wives.
“In many cultures, particularly in east Africa, in order to get married you have to give livestock to the bride’s family,” Glowacki explained.
“We refer to it as bridewealth. If you don’t have cows, you simply cannot get married. It doesn’t matter how handsome you are or how much status you have, if you don’t have cows to give the bride’s family, you cannot get married.”
Though he found evidence that violence offers a benefit to warriors, Glowacki said he’s more interested in a bigger question.
“The overriding question I’m interested in is how humans cooperate, and one type of cooperation is participating in intergroup conflict,” he said. “Why do people do things that benefit their group if they have to pay a cost?
“For the Nyangatom there are no formal institutions governing society, and yet they manage to make a living from one of the toughest landscapes on Earth, and they do that through cooperation.”
Cooperation plays a key role in virtually every aspect of Nyangatom life, he noted.
“I set out to study who herds together, who digs water holes together, who plants together, and also who participates in conflict events together,” he added.
“I conducted interviews about the raids, and collected reproductive histories by asking how many wives raiders have, how many children each has had, how many are alive, how many died and how they died.”
In an analysis of 120 men, Glowacki found that those who participate in more raids had more wives and more children over the course of their lives.
But while raiders benefit from taking part in conflict, the lack of an immediate payoff helps to keep violence in check, he postulates.
“We don’t have quantitative data to that effect, but there are some groups in neighboring Kenya where raiders who capture cows in a raid don’t have to give them to the elders or they can sell them at a market for money, and the violence is significantly greater,” he said.
“The Nyangatom have a mechanism that mediates the benefits the warriors receive. There is a lot of status and privilege that comes with participating in raids. When you come back to the village, the women are singing and people are parading. They’re celebrating you, but you still go home alone.”
The study was published in the Proceedings of the National Academy of Sciences.
Source: Harvard University