In youth, parties with as many friends as possible are popular – with increasing age, however, people tend to focus more on quality than quantity. This tendency towards smaller but closer circles of friends has now also been established by researchers in aging male chimpanzees. The observation thus calls into question a previous explanation of the phenomenon, which is connected with the complex future thinking of humans. It shows that the maturation of friendship systems has more fundamental causes that also play a role in our closest relatives in the animal kingdom.
The term friendship is not that easy to define. Fundamentally, friendship describes a relationship based on mutual affection that is associated with trust and helpfulness. However, people have very different ideas about this concept and the characteristics of their friendly networks differ significantly. As studies in different cultures show, age also plays a role. In their youth, people tend to build larger, but more relaxed, groups of friends. With increasing age, the network then usually becomes smaller, but more profound: People focus more on closer, more positive relationships – they apparently prefer to spend their time with “real friends”.
The finitude of life in mind?
So far, the so-called socio-emotional selectivity has been an explanation of this tendency in psychology. According to this, the growing awareness of one’s own finitude plays a role with increasing age: people would rather devote their remaining lifetime to close friends than to dealing with looser contacts or looking for new ones – so the assumption. However, it remains questionable whether people actually deal with the topic in this way. Against this background, the researchers led by Alexandra Rosati from the University of Michigan in Ann Arbor have now investigated the question of how friendship systems develop in our closest relatives in the animal kingdom over the course of life.
The results are based on observations of wild chimpanzees (Pan troglodytes) in the Kibale National Park in Uganda. The behavior of the animals has been systematically documented there for 25 years. As part of the study, the researchers analyzed the relationships of 21 males aged 15 to 58 years. The focus was on developments in male friendships, as female animals are more difficult to identify because they change groups more frequently. For the study, the researchers examined how often the males made contact and in what way. As a sign of the intensity and reciprocity of friendships among certain individuals, they rated the behavior when grooming each other.
Parallels to chimpanzee friendships
“Principles emerged that are similar to those in humans,” says Rosati, summing up the results of the analyzes. In contrast to the younger ones, the older male chimpanzees therefore spent significantly more time with individuals with whom they had developed intensive relationships over many years. These old friendships were characterized by their reciprocity, which was reflected in the mutual grooming behavior. In younger chimpanzees, on the other hand, the researchers observed more often one-sided relationships in which care was not always reciprocated. “In young animals, we have noticed this less intense form of friendship and then, as they get older, they spend more and more time with individuals who are equally willing to give,” says co-author Zarin Machanda of Tufts University in Medford . “The animals really invest a lot in these relationships,” says the behavioral scientist.
Now the focus is now on people again. The underlying principles of the phenomenon remain questionable, but the explanatory approach of socio-emotional selectivity now appears implausible in view of the findings in chimpanzees. “Even though chimpanzees are very intelligent, they don’t understand that they’re going to die,” says co-author Richard Wranham of Harvard University in Cambridge. “Apparently another process shapes why their relationship systems change in the observed way with increasing age. This begs the question: does this also apply to humans? It is possible that we will see systems of behavior that go back evolutionarily to our common ancestors about seven or eight million years ago, ”says Wranham.
Source: Harvard University, Technical article: Science, doi: 10.1126 / science.aaz9129