Self-Domestication Syndrome

Description

From the Wikipedia:

"Hare and Woods argue that instead, humans underwent extreme selection for prosociality, and that cognitive changes occurred by accident.

Domestication is a process of human induced artificial selection that causes marked changes in an animal compared to their wild relatives. Collectively called the domestication syndrome, these changes include physiology (increases in serotonin, oxytocin), morphology (skull shape and size, tooth size, floppy ears, curly tails, star mutations), behavior (reproductive cycle, juvenile behavior), and social cognition (increase in cooperative communicative abilities). Different domesticated animals have different combinations of these changes. Until recently, it was poorly understood why different species of domesticated animals developed which traits. However, one trait that all domesticated animals share is a reduction in aggression compared to their wild relatives.

Pioneering experiments where Siberian foxes were experimentally domesticated demonstrated that domestication is directly caused by intense selection against aggression. Over 50 generations, breeding only the friendliest, non-aggressive foxes, whose fear towards humans was replaced by attraction, led to a cascade of the physiological, morphological, behavioral, and cognitive changes apparent in other domesticated animals.

The process of self-domestication is similar, but instead of humans actively selecting against aggression, natural selection favors the process instead. As an example, in our closest living relatives, bonobos, self domestication can occur entirely without human intervention. Compared to our other closest living relatives, chimpanzees, bonobos are much less aggressive, and have never been observed to kill their group members or attack neighboring groups. Recent work shows that the friendliest bonobo male is more reproductively successful than the most despotic chimpanzee. Thus natural selection could favor reduced aggression in bonobos, which would have led to the domestication syndrome. Indeed, compared to chimpanzees, bonobos have changes to their morphology, (reduced cranial size, canine dimorphism, and depigmentation of the lips and tail tufts), physiology (changes to serotonin receptors and testosterone response), behavior (more juvenilized socio sexual behavior and play) and social cognition (increase in cooperative abilities).

If self domestication could occur in bonobos, then it may also be possible in our own species. Hare and Woods propose that natural selection favored increased in-group prosociality over aggression in late human evolution. As a by-product of this selection, humans are predicted to show traits of the domestication syndrome observed in other domestic animals, including early-emerging cooperative communicative abilities.

Drawing on comparative, developmental, fossil, and neurobiological evidence, Hare and Woods propose that late human evolution was dominated by selection for intragroup prosociality over aggression. As a result, modern humans possess traits consistent with the syndrome associated with domestication in other animals. Increases in cognition, particularly related to cooperative communicative abilities, occurred by accident."

(https://en.wikipedia.org/wiki/Survival_of_the_Friendliest)

Discussion

Robin Henderson:

(from a review of the book: The Goodness Paradox: The Strange Relationship Between Virtue and Violence in Human Evolution by Richard Wrangham)

"What factors were responsible for the self-domestication of humans?

Homo sapiens are thought to have arisen about 300,000 years ago.

Based on DNA analysis and findings from paleontology, Wrangham estimates that the self-domestication process began approximately 400,000 to 600,000 years ago. It started among the “Mid-Pleistocene Homo,” an early forerunner of Homo sapiens.

The book states that “the execution hypothesis” is key to the process. Capital punishment practiced in small human groups gave rise to a less aggressive psychology that uniquely defines Homo sapiens compared with other primate species.

Executing the most antisocial individuals selected against aggression in favor of greater docility and conformity.

There are physical characteristics associated with human self-domestication, including neotenous facial features, reduced sexual dimorphism, and smaller teeth. Our ancestors, before the self-domestication, had a more mature appearance, larger brows, larger teeth, and greater visible sex differences existed between men and women.

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.

Relatedly, as Christopher Boehm and other anthropologists have found, hunter-gatherer communities are largely egalitarian. At least among the adult men.

Wrangham gives an example from the Ona (Selk’nam), a nomadic people in South America:

“A certain scientist visited our part of the world and, in answer to his enquiries on this matter, I told him that the Ona had no chieftains, as we understand the word. Seeing that he did not believe me, I summoned Kankoat, who by that time spoke some Spanish. When the visitor repeated his question Kankoat, too polite to answer in the negative, said: ‘Yes, Señor, we the Ona, have many chiefs. The men are all captains and the women are sailors.”

Among some hunter-gatherer bands, leaders, headmen, and chiefs do exist. But they tend not to hold much power.

Their main purpose is to assist with consensus-seeking when the group needs to make important decisions.

For example, the Mae Enga of Highland New Guinea will discuss their options for warfare and raiding at length. Every man has the option to contribute to the discussion. The leaders within the community maintain a low profile.

As group opinion sorts itself, and a consensus appears to emerge, a leader will exert his limited influence to help crystallize an agreement. But they tend to do this very judiciously, lest they elicit collective scorn from the other men.

Hunter-gatherer communities do not jump straight to executions to control and eliminate hostile males. They start out with softer approaches first, such as leveling mechanisms—norms to constrain people’s egos.

For instance, the book quotes anthropologist Elizabeth Cashdan:

“The proper behavior of a !Kung [Ju/’hoansi] hunter who has made a big kill is to speak of it in passing and in a deprecating manner; if an individual does not minimize or speak lightly of his own accomplishments, his friends and relatives will not hesitate to do it for him.”

Among the Ju/’hoansi hunter-gatherers, people were eight times more likely to deliver criticism than praise.

Similar observations have been made by anthropologists observing modern hunter-gatherer communities. Shaming, teasing, ridicule, and laughter are all used to cut down men who might believe themselves to be better than the others.

More drastic measures include shunning or ostracism, which are often effective because social exclusion tends to be deeply painful. As they say, there’s a reason why solitary confinement is considered by prison inmates to be the worst punishment.

Language was key to the ability to form conspiracies to take out domineering aggressors. It gave humans the ability to murmur about how much you resent some other individual, gauge the reactions of your companions, and coalesce around the decision to impose a penalty.

The capability to quietly and quickly communicate birthed many tools of social control, from ridicule to gossip, all the way up to ostracism and killing.

Wrangham illustrates how such executions work with an example from the Yanomamö hunter-gatherers. Some of the men in the group were annoyed by the arrogance and bullying by a particular male. One day, they encouraged the bully to climb a tree to extract honey. He agreed, and laid down his weapons before climbing up.

His assassins collected the bully’s weapons and merely waited for him to come down before easily killing him."

(https://robkhenderson.substack.com/p/the-distinctiveness-of-human-aggression?)