Scientists Confirm that Chimps, Like Humans, Go to War

It's obvious that humans are fundamentally different from every other animal species. It's not so easy, though, to identify the specific traits that make Homo sapiens so special. Scientists realized long ago that other animals make tools, play jokes and even have a sense of justice and altruism — all things we once thought were unique to our species.
Now a paper in the journal Current Biology has added another behavior to the list of what other animals share with us — and this one isn't quite so charming. After years of field observations in Uganda's Kibale National Park, John Mitani of Michigan State University and several colleagues have concluded that chimps wage war to conquer new territory.
"We already knew that chimps kill each other," says Mitani. "We've known this for a long time." What scientists didn't know for sure, at least in cases in which groups of chimps banded together to kill others, was why. One hypothesis, advanced more than a decade ago by anthropologist Richard Wrangham, was the idea of territorial conquest; circumstantial evidence from both Gombe and Mahale National Parks in Tanzania bolstered the theory.
In Mahale, for example, male members of one group mysteriously vanished, and another group then expanded into what had been their land — suggestive but not conclusive. In Gomba, an existing group dissolved into civil war, resulting in killing and land takeovers. But it's hard to say what the casus belli was and thus impossible to know if territorial combat was a key motivator.
Mitani, for the first time, has gathered direct evidence of deliberate warfare. From 1999 to 2008, he and his colleagues actually observed 18 chimp-on-chimp killings, 13 of which took place in the homeland of a single neighboring group. Then, says Mitani, "last year, all of a sudden, [the aggressors] made this big land grab," moving into the territory where the 13 victims had lived. "It isn't rocket science," he says. "We put two and two together and got four."
Time/By MICHAEL D. LEMONICK/continue reading