Why are chimpanzees so aggressive?

[Image Gallery: Lethal Aggression in Wild Chimpanzees] As one of humanity's closest living relatives, chimps can shed light on the evolution of people, such as when humans adopted warlike behaviors, Wilson said. "Studies of chimpanzee violence have been especially influential in how people think about the origins of human warfare," Wilson explained. read more

Chimpanzees need to compete against each other for the resources, since there is never plenty and to spare for everyone, so they evolved as fiercely territorial animals. I suspect this is also why chimpanzees are omnivores; they need to get their hands on any food possible. read more