Chimpanzees and bonobos bear in mind their buddies many years after being separated | Science | EUROtoday

Despite having gone 26 years with out seeing his sister Loretta and his nephew Erinthe bonus Louise He acknowledged them within the pictures that the scientists confirmed him, stopping his gaze on his household. Like her, different bonobos and chimpanzees have proven to have a excessive social reminiscence. In pioneering work, members of each species remembered companions from the group to which they’d belonged way back. The reminiscence was deeper if the valence of the connection was constructive. That is, in the event that they have been buddies. For the authors of the work, this capability that they share with people is on the foundation of advanced societies.

The concept of ​​investigating whether or not nice apes are able to remembering these they know arose from the personal expertise of the scientists with whom they interacted. They noticed that the animals acknowledged them after they returned to go to them after a yr, two or 5. To verify this, a gaggle of primatologists, anthropologists and psychologists designed an experiment through which they confirmed two photographs on the identical time on a display. One featured a former member of the group to which the individual watching belonged, however who had been gone for a very long time (as a consequence of having died or being transferred from one other facility). In the opposite, one other specimen of his species, however utterly unusual. The monitor had a system to detect eye actions. The experiments have been carried out with 26 chimpanzees and bonobos from the Edinburgh Zoo (United Kingdom), Planckendael (Netherlands) and the Kumamoto Sanctuary (Japan). The picture slides solely lasted three seconds. The primatologist on the University of Saint Andrews (United Kingdom) and co-author of the work Josep Call explains the brevity: “You put a child in front of a problem and he looks and looks. Chimpanzees don’t do it like that. They look to one side, then to the other, and back to this side. Your attention is distributed in a different way. That’s why you have to give them brief tests to capture their attention at that moment.”

In these tests, both the chimpanzees and the bonobos spent an average of 0.24 seconds more looking at the images of those who had been their group mates, as detailed in the scientific journal PNAS. And the memory was lasting. On average, those who carried out the trials had gone five and a half years without seeing those who appeared in the images.

“There were no differences between chimpanzees and bonobos,” Call remembers. Both species are, from an evolutionary viewpoint, the closest family of people. Between six and 9 million years in the past the three lineages separated, however each animals share 98.7% of their genome with people.

Recognition is basic in life. It allows you to remember that place where food was abundant or that that snake is dangerous. But not only events and places are remembered. Humans also preserve relationships and the emotions associated with them in their memory. The authors of the trials saw that the great apes also do it: the participants of the two species and in the three countries focused their gaze more on the group mates with whom they had had positive interactions, what in a human context would be called friendship. For Professor Christopher Krupenye of Johns Hopkins University (United States), an expert in animal cognition and senior author of the research, “this suggests that it is not just a matter of familiarity with something, but that they preserve dimensions about the quality of those social relationships.” ”. Previous work has shown that primates that cultivate social ties reproduce more, which would give an evolutionary advantage to friendship.

In the most extreme case, the bonoba Louise He remembered his family even though 26 years had passed, dedicating more time to them in the eight passes they made to him. For a species that has at most a 60-year life expectancy, that is a long time, which would indicate that the strength of relationships is not diminished over the years. But the authors cannot categorically affirm that the long social memory of Louise It was due to kinship and not just group membership. In the sample, there was only this family relationship. For this reason, as the psychologist at the University of California, Berkeley, and first author of the study, Laura Simone Lewis, says in an email, they did not specifically measure how much they looked at family members. “In fact, in the main analyses, we excluded the cases of relatives so that the mechanisms of recognition of relatives did not interfere with the recognition patterns.” But it is one of the lines of research that leaves open to the future: whether, like friendship, family also weighs or does more in social memory.

“We humans like to think that everything we do is unique and here we show that it is not”

Josep Call, primatologist at the University of Saint Andrews (United Kingdom)

This finding makes bonobos and chimpanzees the animals with the longest lasting social memory, almost immune to the passage of time. In humans, the so-called forgetting curve is very pronounced in the first 15 years that they spend without seeing someone they love, but after that what remains, remains forever. That all three species share this capacity gives clues to social memory. Call highlights this: “We humans like to think that everything we do is unique and here we show that it is not, so do chimpanzees and bonobos.” But other species, such as dolphins, are also capable of distinguishing the vocalizations of their companions despite the passage of time apart. “Once you get to a type of behavior in which individuals are not only part of a group, but are individuals whom others can identify as Charlie, Juanita o Nuggetfrom there the type of social complexity that is established and that can potentially evolve is much greater,” concludes the primatologist.

Julia Fischer is also a primatologist, in her case from the German Primate Center. Like the authors of the work, in which she has not intervened, the same thing happened to her: “I saw the baboons that she had studied for a year and a half in the Okavango Delta again five years later. And curiously, the animals I had studied treated me like someone they knew (ignoring me), while the new ones that had been born since my departure or that had immigrated to the group, treated me like a stranger.” It is an anecdote, but it points in the same direction as the maintenance of social memory, which Fischer summarizes: “Recognizing the members of your group has a clear survival value and, of course, it is also necessary to have a good memory, just as the we have, a precondition for human friendship and drama.”

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