September 18, 2014

Murderous chimps

Nature 513, 414–417 (18 September 2014) doi:10.1038/nature13727

Lethal aggression in Pan is better explained by adaptive strategies than human impacts

Michael L. Wilson et al.

Observations of chimpanzees (Pan troglodytes) and bonobos (Pan paniscus) provide valuable comparative data for understanding the significance of conspecific killing. Two kinds of hypothesis have been proposed. Lethal violence is sometimes concluded to be the result of adaptive strategies, such that killers ultimately gain fitness benefits by increasing their access to resources such as food or mates1, 2, 3, 4, 5. Alternatively, it could be a non-adaptive result of human impacts, such as habitat change or food provisioning6, 7, 8, 9. To discriminate between these hypotheses we compiled information from 18 chimpanzee communities and 4 bonobo communities studied over five decades. Our data include 152 killings (n = 58 observed, 41 inferred, and 53 suspected killings) by chimpanzees in 15 communities and one suspected killing by bonobos. We found that males were the most frequent attackers (92% of participants) and victims (73%); most killings (66%) involved intercommunity attacks; and attackers greatly outnumbered their victims (median 8:1 ratio). Variation in killing rates was unrelated to measures of human impacts. Our results are compatible with previously proposed adaptive explanations for killing by chimpanzees, whereas the human impact hypothesis is not supported.

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6 comments:

Justin Loe said...

Of interest from earlier research: "Chimpanzees had rates of aggression between two and three orders of magnitude higher than humans."
reference:
http://link.springer.com/article/10.1007%2Fs10329-005-0140-1

batman said...

The observer observing the change of the observed as the observer is observed by the observed the observer observes.

Now, who's having no impact - on who?

DocG said...

The fact that bonobos are far less aggressive than chimps suggests that chimp violence could be cultural rather than biological. And the fact that a great many African foragers, including both Pygmies and Bushmen, tend to lack any trace of institutionalized violence, makes them closer to Bonobos than Chimps in any case. Such groups also resemble Bonobos in their strong tendencies to share and the relatively high degree of female independence and assertiveness. The notion that we get our violent tendencies from "violent genes" shared with chimps is almost certainly false.

barakobama said...

" Pygmies and Bushmen, tend to lack any trace of institutionalized violence, makes them closer to Bonobos than Chimps in any case"

You shouldn't expect such undeveloped and small societies as those of the Bushmen and Pygmies to have institutionalized violence. That's largely a modern thing. Most people in history didn't have an official military like for example America does.

I bet humans are more similar to Chimps when it comes to aggression. We use our weak and small size as an excuse to say all animals are more violent than we are. We're constantly fighting each other.

We can't use advanced societies in Eurasia as an excuse for war, raid, conquest, and murder, native Americans for example did the same thing. Violence in humans has nothing to do with being advanced, it's our instinct. When we become more advanced overtime we just find more effective ways to kill each other. There are plenty of prehistoric examples of extreme human violence. The famous Otzi the Iceman for example did not die of natural causes and buried he was murdered.

andrew said...

Notably, the gender balance of murder in chimps is almost exactly the same as in humans.

DocG said...


@barakobama:
"You shouldn't expect such undeveloped and small societies as those of the Bushmen and Pygmies to have institutionalized violence. That's largely a modern thing."

"Violence in humans has nothing to do with being advanced, it's our instinct."

These two statements appear to contradict one another.

In any case, the fact that those societies with the deepest genetic roots lack institutionalized violence makes it hard to claim that violence is some sort of instinct inherited from ancestors we share with chimps. Sure, there are many foragers who engage in feuding, raiding and warfare on a regular basis. But those rooted most deeply in our phylogenetic trees do not.

Also it's important to remember that chimps are the ONLY primates, and indeed the only mammals, aside from humans, who prey upon their own kind. They are the exception, not the rule. As I see it, endemic violence is a product of historical contingencies, not genetically based "instincts."