It was once believed that war-like violent behavior among social groups was exclusively a human trait. That is, until Jane Goodall observed a group of chimps in Tanzania’s Gombe Stream National Park in 1971 break out in a violent four-year civil war that eventually resulted in the systematic murder of all members of the losing faction.

For decades, researchers have debated what ultimately spurred the gruesome civil war. But now for the first time, modern analysis of social networking behavior is being applied to the case, revealing some of the complicated social dynamics at play when chimps tragically turn to war, reports NBC News.

The study was conducted by Joseph Feldblum, a Ph.D. student in evolutionary anthropology at Duke University, and his team, consisting of Sofia Manfredi, Ian C. Gilby and Anne E. Pusey. They applied several programs that analyze social networking behavior to the data from Goodall's copious notes of the event, but one program, called UCINET, was especially revealing.

The analysis tool looked at the chimp comings and goings — a social network of sorts — and showed that one chimp in particular, an alpha male named Leakey, was a keystone figure in the social dynamics of the pre-war chimp society. Leakey's leadership served as the social glue that held the various factions together. But after his death, the factions dispersed, much in the same way that a power vacuum forms when a dictator dies.

The majority of the chimps that hailed from the northern part of the original group's territory rallied around a male named Humphrey, while chimps from the south pledged their loyalty to two brothers, Hugh and Charlie. Researchers now believe that these social divisions were present even before Leakey's death, for the same reasons that humans form closer bonds with individuals they regularly interact with. For example, chimps often have "core areas" where they congregate to forage — and that was the behavior that Goodall was tracking. These patterns are what eventually coalesced into the new splintered factions.

Because the northern group was larger and more unified, it was able to gradually pick off the members of the southern group one by one over the course of a wretched four-year period.

Chimp attacks usually begin with a group of males going on patrol, listening quietly near the border of their territory. If they discover another group of chimps with similar strength, the two sides usually shout back and forth and size each other up without too much physical violence. But if the patrol happens upon a smaller group, they will occasionally rush in to scatter them until a member of the smaller group is isolated. The lone chimp will then be held down, savagely bitten, hit, kicked and dragged, often leading to death. This is how the southern Gombe group was systematically decimated.

"It’s really horrible and violent," said Feldblum. 

Since Goodall's first observations of war-like behavior among chimps, researchers have learned that, while this kind of chimp violence doesn't happen everyday, it isn't that uncommon either. It would seem that violence and war is not the exclusive terrain of human behavior after all.

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