Was Hugging a "Technique of Peace"? Conflict Avoidance Taught by Apes from 6 Million Years Ago

When you are about to have a clash of opinions with someone, sometimes placing a gentle hand on their shoulder or exchanging a handshake with a close acquaintance can change the atmosphere more effectively than words.

Is such physical contact a sophisticated form of communication developed exclusively by humans who use language? Or is it an ancient "social technology" inherited long before we had language?

Research conducted by an international team centered at Durham University in the UK on bonobos and chimpanzees suggests the latter possibility.

According to the study, individuals that engaged in more affiliative physical contact, such as hugging, touching, and kissing, just before tensions over food escalated, tended to spend more time eating peacefully in close proximity to others afterward.

Physical contact not only repairs damaged relationships after a conflict but may also be used to alleviate tension before a conflict begins, helping to navigate competition peacefully.

The "Five Minutes of Tension" Before Food Appears

For wild animals, food is a precious resource directly linked to survival. Especially in situations where many individuals gather in a limited space, tension arises over who eats first and who eats next to whom.

The research team observed semi-wild bonobos and chimpanzees living in the Lola ya Bonobo Sanctuary in the Democratic Republic of the Congo and the Chimfunshi Wildlife Orphanage in Zambia.

The study focused on five groups, totaling 116 individuals. Researchers filmed the five minutes just before food was provided in a limited shared space, meticulously recording which individuals touched whom and what kind of contact it was.

They also examined how long individuals could eat close together and whether any aggressive behavior occurred before and after feeding. The analysis covered 60 feeding sessions, with total observation time exceeding 10 hours.

The results showed that in both bonobos and chimpanzees, individuals that engaged in reassuring contact before feeding tended to spend more time eating with their peers afterward.

While it remains possible that "they touched because they were close, and they ate together because they were close," the timing of the contact is at least significant. Just before tensions over food peaked, they engaged in behaviors that seemed to reaffirm their relationships.

Reestablishing Relationships Before Conflicts Arise

Previous studies on ape physical contact have often focused on behaviors that console individuals affected by conflicts or reconcile conflicting parties after a fight.

This study, however, focused on the stage before conflicts even begin.

When faced with limited food, even usually close companions can become competitors. Therefore, exchanging hugs or contact before actual competition begins may convey the message, "We will compete, but I don't intend to ruin our relationship."

In human society, people shake hands before important negotiations, and athletes hug before and after sports matches. This serves not only as a formality but also as a way to separate competition from relationships.

Even if you need to compete with someone, you don't have to make them an enemy. Physical contact may function as a non-verbal signal to confirm that boundary.

Among Bonobos, Females; Among Chimpanzees, Males

Interestingly, the combinations where the effect of contact was most pronounced differed between the two species.

In bonobos, the strongest tendency was observed in female pairs. In bonobo society, it is known that unrelated females form cooperative relationships and support the order of the group. The stronger the bond between females, the more peacefully they can handle competition over food.

On the other hand, in chimpanzees, the relationship between contact and co-feeding was stronger in male pairs. Male chimpanzees remain in their birth groups while forming alliances with other males. They have complex relationships, competing for status while needing each other as cooperative partners.

Thus, while the form of physical contact itself is similar, the individuals for whom it is particularly important differ according to the social structure of each species.

It cannot be simply categorized that bonobos are peaceful and chimpanzees are aggressive. Both species have developed networks of contact suited to their societies to balance competition and cooperation.

"Dangerous Trust" of Putting a Hand in the Mouth

The research team was particularly surprised by the highly risky contact shown by some chimpanzees, especially males.

In tense situations before meals, they would sometimes put their fingers or hands into the mouths of others.

Inserting a hand into the mouth of a chimpanzee, which has sharp canines and strong jaws, could easily lead to serious injury if something goes wrong. Such an action cannot be done without trusting that the other will not harm them.

Researchers suggest that this behavior may serve as a strong signal of "I trust you."

Trust cannot be established merely by observing the safety of the other. Sometimes, it is confirmed by showing one's vulnerability and giving the other the opportunity to harm.

Offering the hand that holds a weapon for a handshake, turning one's back, or confiding a secret—many actions in human trust relationships share this structure.

The act of putting a hand in a chimpanzee's mouth seems to teach that trust is not about eliminating danger completely but about entrusting oneself to the other amidst the presence of danger.

The "Reassurance Train" of Successive Hugs

One of the triggers for this research was an impressive behavior observed in a socially tolerant group of chimpanzees.

Initially, one male would hug another male from behind. Then, another male would join from behind, followed by yet another. Eventually, multiple chimpanzees would line up, calming down while hugging each other.

Researchers called this scene the "reassurance train."

At first glance, it might look like a children's game. However, considering it was done in situations where tension over food was high, it may have been a behavior to adjust the mood of the entire group.

The contact of one individual would draw out contact from the next, spreading reassurance throughout the group. The effect of reducing tension might have been cascading as touched individuals touched others.

The atmosphere of a society is not determined solely by systems or rules. Small interactions between individuals accumulate, forming the expectation that "resources can be shared without fierce conflict in this group."

The reassurance train can be seen as a visible manifestation of that expectation.

Has Physical Contact Continued for 6 Million Years?

Bonobos and chimpanzees are the closest living apes to humans. The fact that both species use similar physical contact in similar situations to alleviate tension suggests that the foundational behavior may have existed in the common ancestor of humans.

It is believed that the lineage connecting humans, chimpanzees, and bonobos split over 6 million years ago.

However, we cannot directly confirm scenes of hugging by ancestors 6 million years ago, as behavior does not fossilize.

Comparative studies estimate the possibilities of traits in common ancestors based on features shared by current closely related species. Therefore, it is appropriate to understand that "it is highly likely to be an ancient ability derived from the common ancestor" rather than definitively stating "the ancestor did the same thing 6 million years ago."

This caution is also necessary when applying research findings to human society.

Just because a link between contact and social tolerance was found in apes doesn't mean all human conflicts can be resolved by hugging. Unwanted contact can cause fear or discomfort rather than reassurance. The meaning of being touched varies greatly depending on culture, relationships, positions, and past experiences.

The important thing is not to make contact itself a panacea but to focus on the possibility that pre-verbal communication has long been used as a means to confirm relationships and adjust tension.

On Social Media: "Necessary for Humans" and "Caution in Evolutionary Conclusions"

This study was just published on July 21, 2026, and as of the day after its release, extensive comments or widespread discussions about the research itself are not yet easily observable.

Meanwhile, looking at related research on ape social behavior shared on social media, reactions are largely divided into two.

One reaction is to take it as a lesson for modern society, saying, "Humans also need to confirm relationships before conflicts" and "In a society centered on online interactions, non-verbal signals of reassurance might be important."

Photos of hugging chimpanzees or bonobos have a strong emotional appeal, making them well-suited to humorous interpretations like "They seem more peaceful than humans" or "We need a reassurance train before meetings."

The other reaction is a cautious stance on expressions related to evolution.

When Durham University previously introduced related research on social tension management through sexual behavior in bonobos and chimpanzees on social media, comments questioning "how much can be inferred about the behavior of ancestors 6 million years ago from the behavior of current apes" were also received.

This criticism is also important when reading this study. While the possibility inherited from a common ancestor can be scientifically examined, past behaviors were not directly observed. The research indicates the possibility that physical contact has an ancient evolutionary basis, not that it proves specific historical behaviors.

On social media, the straightforward conclusion of "peace through hugs" tends to spread easily. However, the truly intriguing aspect lies not just in the presence or absence of contact but in who touched whom, at what timing, and how much risk was involved.

"Peace Was Achieved Because of Contact" Cannot Yet Be Definitively Stated

The results of this study show that individuals with more contact before feeding tended to spend more time eating together afterward.

However, at this stage, it cannot be completely concluded that physical contact directly produced tolerance.

It is possible that there was more contact because the individuals already had good relationships, allowing them to eat together. Additionally, it may have been that dangerous contact was permitted because the group was tolerant.

In fact, the relationship between contact and co-feeding was particularly clear in groups that were already socially tolerant. This suggests a bidirectional relationship where contact might create a tolerant atmosphere, and a tolerant atmosphere might enable contact.

The research team intends to further investigate whether specific pairs that had contact before feeding could eat calmly later, or if the risk of conflict decreases.

Moreover, it is also an important research topic to determine whether stress hormones in both the toucher and the touched actually decrease due to physical contact.

If behavioral observations and physiological changes are linked, it could more clearly explain whether physical contact is merely an expression of intimacy or a mechanism that directly adjusts tension.

Evolution Is Not Just a "History of Competition"

The evolution of humanity is often described as a history of competition, where strong individuals win and compete for limited resources.

Of course, competition and aggression are important elements of evolution. However, for animals living in groups, resolving every conflict through violence is a significant burden.

Injuries can be detrimental to survival, and losing cooperative partners can make it difficult to secure food, raise offspring, and respond to external threats. The ability to adjust competition so that it does not destroy the group is as necessary as the ability to win competitions.

The hugs, hand contacts, kisses, dangerous mouth contacts, and reassurance trains shown by bonobos and chimpanzees suggest that evolution has continually selected not only the "power to fight" but also the "power to maintain relationships while fighting."

Touching may be both an expression of kindness and a practical action to maintain a complex society.

Before the advent of language, laws, or contracts, our ancestors may have communicated their intentions not to harm others and to continue relationships despite competition through body warmth, pressure, and proximity.

In modern human society, consent and cultural consideration are indispensable for physical contact. Nevertheless, the principle that actions reassuring others can alleviate social tension remains unchanged.

Making eye contact, speaking in a calm voice, confirming the other person's intentions, maintaining a safe distance, and holding hands with consent if the person is close.

Behind these small signals we use in society flows a history of ancient communication that may extend over 6 million years.

Sources

・Phys.org. Referenced for the study overview, subjects, the relationship between pre-feeding physical contact and co-feeding time, and researchers' comments.
https://phys.org/news/2026-07-humans-closest-ape-physical-social.html

・Proceedings of the Royal Society B published paper "Reassuring body contact promotes social tolerance in bonobos and chimpanzees." Primary source of the study.
https://doi.org/10.1098/rspb.2025.3190

・Doctoral thesis by Jake Brooker submitted to Durham University. Referenced for the research background on consolation, pre-feeding contact, and the evolution of empathy in bonobos and chimpanzees.
https://etheses.durham.ac.uk/14972/

・Scimex research release. Referenced for information on research methods, target facilities, research funding, and future research topics.
https://www.scimex.org/newsfeed/hugs-may-be-an-ancient-tool-for-social-harmony-ape-study-shows

・LinkedIn post related to research by Durham University. Referenced for cautious reactions on SNS regarding inferences linking ape behavior to common ancestors 6 million years ago.
https://www.linkedin.com/posts/durham-university_did-you-know-that-using-sex-to-manage-social-activity-7303036804893409280-vjFF

・ChosunBiz Japanese version of Chosun Ilbo's explanatory article. Referenced for reporting expressions on the "reassurance train" and species-specific social structures.
https://biz.chosun.com/jp/jp-science/2026/07/22/LLA62QRIINFMPO4OLOF4ZMULYQ/?outputType=amp##HTML_TAG_212