Chimps with more aggressive, greedy and irritable personalities reach the highest rungs on their social ladder and are more successful at siring offspring than other males in their group. Researchers base their study on 37-year observations of the behavior of 28 chimpanzees in Tanzania's Gombe Park.
Some chimpanzees are more sociable and others more solitary. Some prefer to be calm while some individuals are authoritarian and tend to provoke fights. Within the great primates, chimpanzees are the ones that show the most aggressive and territorial behavior (particularly compared to bonobos)