Friendly signals at the beginning and at the end: As is well known, special communication patterns shape our social interactions. This apparently also applies to our closest relatives in the animal kingdom, according to a study: Chimpanzees and bonobos also display certain behaviors in order to initiate and complete interactions. Interestingly enough, how much the animals make an effort to communicate also depends on their relationships with the bonobos. Overall, the behavior of our relatives reflects the basic principles of human courtesy, say the scientists.
Together we are strong: The complex ability to cooperate is a key element of human success. As is well known, the underlying social behavior is linked to many rules – those who do not adhere to them can expect negative reactions from their fellow human beings. This system also includes the feeling of a certain obligation towards people with whom we have established contact. This is reflected in our manners: For example, we clarify the beginning of interactions through certain phrases, gestures and our body language. The same applies to the end of each contact. On the other hand, anyone who simply turns away and leaves without a word or a goodbye gesture is behaving impolite or deliberately snubbering their counterparts.
Questioning look at our relatives
These complex behaviors are typically human, one might think – but there are already indications that great apes also feel obliged when dealing with conspecifics: If two animals are interrupted during a joint activity, they then take it up again with the same partner , researchers have already observed. But do they also show special communication signals at the beginning and end of interactions – like we do? The researchers led by Raphaela Heesen from Durham University answered this question through a behavioral study on chimpanzees kept in zoos (Pan troglodytes) and bonobos (Pan paniscus) followed up. In total, they analyzed the communicative characteristics of 1242 interactions between two animals.
As they report, their evaluations confirmed: In both great ape species, individuals looked at each other with remarkable frequency and showed communicative signals to both begin and end interactions such as mutual grooming or play. This was even more pronounced with the bonobos, known as “hippie chimpanzees” because of their “special” social behavior: they exchanged input signals and mutual glances in 90 percent of the cases – the biologists observed this in around 70 percent of the interactions with the chimpanzees. In both species, the end was more often characterized by conspicuous communication behavior: in 92 percent of the cases in the bonobo and 86 percent in the chimpanzee interactions. The signals included gestures such as touching each other, holding hands, butting the head or looking at each other, the researchers report.
Parallels to people
As part of their study, they also recorded the social relationships between the respective partners – the special friendship relationships or the status in the hierarchy. It was found that with bonobos, the duration of entry and exit communication tended to be shorter the closer the individuals were. According to the authors, this pattern is similar to how we as humans communicate with others: “When you interact with a good friend, you are less likely to make an effort to communicate politely,” says Heesen.
Interestingly, the researchers found no connection between behavior and social relationships in the chimpanzees. As they explain, this difference could have something to do with the different foundations of social structures in chimpanzees and bonobos: Bonobo communities are more intensely shaped by friendships and alliances than the dominance-based systems of chimpanzees. Maybe that’s why the manners of the bonobos are a bit more complex.
As the scientists finally emphasize, the results also shed light on the development of behaviors in the common evolutionary history of chimpanzees, bonobos and humans: The results suggest that the behaviors associated with the feeling of “commitment” already existed in our last common ancestor existed, according to the scientists. “Behavior doesn’t petrify – you can’t dig up bones to see how behavior evolved. But you can study our closest living relatives to gain clues, ”says Heesen.
This video shows the apparently typical behavior at the beginning and at the end of a playful interaction between two chimpanzees. (Credit: Raphaela Heesen and Emilie Genty)
Source: Cell Press, technical article: iScience, doi: 10.1016 / j.isci.2021.102872