Primates are 150 to 550 more violent than humans

From The Distinctiveness of Human Aggression by Rob Henderson.  A review of The Goodness Paradox: The Strange Relationship Between Virtue and Violence in Human Evolution by Richard Wrangham.

Single indents are Hendersons words, double indents are Wranghams.  An interesting and detailed essay.  These are mere interesting points.

The “self-domestication hypothesis” is the idea that in the ancestral environment, early human communities collectively killed individuals prone to certain forms of aggression: arrogance, bullying, random violence, and monopolizing food and sexual partners.

Over time, our ancestors eliminated humans—typically males—who were exceedingly aggressive toward members of their own group.

If there was a troublemaker, then other less domineering males conspired to organize and commit collective murder against them.

Women too were involved in such decisions involving capital punishment, but men typically carried out the killing.

Humans tamed one another by taking out particularly aggressive individuals. This led us to become relatively peaceful apes.

[snip]

The fact is, humans are not nearly as violent as our nearest evolutionary relatives.

Comparing the level of within-group physical aggression among chimpanzees with human hunter-gatherer communities, chimps are 150 to 550 times more likely than humans to inflict violence against their peers.

We humans are far nicer to members of our own group than chimps are. Thanks to our ancestors and their ability to plan organized murder. And tear overly dominant males to shreds.

Many people are familiar with the findings that bonobos are more peaceful than chimpanzees.

This is true.

Male bonobos are about half as aggressive as male chimpanzees, while female bonobos are more aggressive than female chimpanzees.

Bonobos are “peaceful,” relative to chimps. But bonobos are extremely aggressive compared to humans.

[snip]

Humans present a puzzle. We are the only species capable of horrific cruelty as well as extraordinary kindness. Think of the Nazis who existed in the same society as those who risked their lives hiding strangers from being killed by them.  

This incongruity gives rise to the perennial question: Are humans naturally good or evil?

In the introduction of the book, Wrangham provides his answer: both.

Informed by evolutionary science, the book states that our biology gives rise to contradictory motives and behaviors.

We are innately good and innately bad.

Wrangham then posits a more useful question: What is the significance of primate behavior for understanding human nature?

In chapter one, the book reports observations of early anthropologists who would encounter “primitive peoples.” These western observers were surprised at how little fighting there was within these communities.

Their peacefulness, however, extended only to members of the same society.

Wrangham writes:

“In 1929, the anthropologist Maurice Davie summarized a consensus understanding that remains true today: people were as good to members of their own society as they were harsh to others. There are two codes of morals, two sets of mores, one for comrades inside and another for strangers outside, and both arise from the same interests. Against outsiders it is meritorious to kill, plunder, practice blood revenge, and steal women and slaves, but inside the group none of these things can be allowed because they would produce discord and weakness.”

In everyday life, humans tend to experience relatively low levels of within-group violence.

But conflict between groups creates conditions for catastrophic death rates. Humans are good at getting along with their peers. And good at extinguishing their adversaries.

[snip]

In the course of evolution, human communities selected against reactive aggression.

In other words, early humans united to inflict penalties (including death) on impulsive and domineering members of their communities.

Wrangham writes:

“For the first time, coalitions of males became effective at deliberately killing any member of their social group who was prepared to use violence on his own behalf and simply did not care what others thought about him. In the end, execution was the only way to stop such a male from being a tyrant…The killing of aggressive males is an alarmingly potent form of social control and a human universal.”

If a man repeatedly irritated his companions in the group with aggressive and selfish behavior, then gradually, a whispered consensus emerged against him.

A conspiracy formed among the other men, and the aggressor was killed.

Throughout thousands of prehistorical generations, those with a high propensity for reactive aggression were targets of execution.

Killing these individuals gradually led humans to have a calmer, less overtly hostile temperament.

[snip]

Wrangham states that self-domestication and morality are intertwined.

Morality can only evolve among a species that is intensely sensitive to social disapproval.

Negative moral judgment is extremely unpleasant for most people.

For our ancestors, cultivating a good reputation was crucial. Troublemakers were ridiculed, ostracized, and sometimes murdered.

Today, we often feel self-conscious even in one-shot interactions with people we will never meet.

This doesn’t make rational sense, until you understand that early humans almost never interacted with anonymous strangers. For them, every social interaction held potentially life-threatening importance. We still carry this psychology with us today. We will endure minor and sometimes even extreme discomfort to avoid the negative judgment of strangers.

Of course, morality has differed throughout time and across cultures. As the book states:

“Society influences what we care about, but evolution has produced the fact that we care.”

In my view, morality is analogous to language.

Both are human universals. But the specifics of each vary by culture and change over time.

[snip]

Wrangham makes good on explaining the book’s title, The Goodness Paradox.

Throughout the book, he uses the term “coalitionary proactive aggression,” which means a group of individuals who come together to deliberately attack a person or another group.

This type of violence is unique to humans.

As Wrangham puts it:

“Tribalism does not distinguish us, nor does reactive aggression. It is coalitionary proactive aggression that makes our species and societies truly unusual.”

[snip]

As the psychologist Jonathan Haidt has observed in the context of university campuses:

“A funny thing happens when you take young human beings, whose minds evolved for tribal warfare and us/them thinking, and you fill those minds full of binary dimensions. You tell them that one side of each binary is good and the other is bad. You turn on their ancient tribal circuits, preparing them for battle. Many students find it thrilling; it floods them with a sense of meaning and purpose.”

Inter-group conflict can take on different forms.

[snip]

As the physician and sociologist Nicholas Christakis has written in Blueprint: The Evolutionary Origins of a Good Society:

“Maybe kindness and hatred are related. Mathematical analyses of models of human evolution suggest that...neither altruism nor ethnocentrism evolved on its own, but they could arise together. In order to be kind to others, it seems, we must make distinctions between us and them.”

And an economist would agree.  Time and materials are scarce.  If we share them with everyone, we risk having nothing and gaining nothing.  If, on the other hand, we can share some of our time and resources to reinforce coalitions with others with common goals, we become more effective in achieving those goals.

But to prioritize those with shared goals, we necessarily must deprioritize those who do not share our goals.  Not because we wish to punish them or harm them but simply because we have limited time and resources to share.  

All this also relates to The Better Angels of Our Nature by Steven Pinker and others.  Aggregate annual death rates among tribal groups are far higher than among settled complex populations.  Small increments of routine violence have a greater impact than occasional large scale violence.