A number of outlets have reported a recently completed study of chimpanzee aggression and killing. Evidently some have hypothesized that chimps killing each other was an unintended consequence of their contact with humans, including loss of habitat. This was despite Jane Goodall’s early reports of chimp violence when human contact was very limited. So analyzing a number of studies of chimpanzee and bonobo violence, the scientists found no correlation between chimp violence and human contact. They also found next to no bonobo violence. Why?
Now this chimp looks pretty reflective but I have no idea of the context. Chimps are known to be pretty aggressive both within their clan reflecting their social hierarchy and between clans over resources. A pretty good Disney movie a couple of years ago, Chimpanzee, showed the good and the bad here. An orphaned youngster was adopted by the alpha male and thus survived, a presumably unusual event and the documentarians thanked their lucky stars that they saw it. This group also had to fight another group repeatedly over a prime food source and these battles were seemingly well organized both on the offense and the defense. Really amazing.
Now bonobos are smaller than chimps and known to be less aggressive. They are entirely promiscuous and solve conflict through physical expression of affection, if I can use that word here, and they are known to be very caring parents. I believe I have read studies showing a higher level of oxytocin, which promotes parental positive feelings, in bonobos than chimps. Some geographic isolation by large rivers has contributed to the separation of these two primate lines, but why the difference in violence is a very interesting question being studied today.
Perhaps the chimp above is pondering his next play like a poker player wondering if the other’s cards are good. Here is a picture of the bonobo, a lover not a fighter.