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Chimpanzees are able to identify their fellow chimpanzees even after several decades, particularly if they had a good relationship.


Our capacity to recall individuals we encountered years ago, whether it be a large group at a school reunion or extended relatives at a wedding, can be advantageous. Recent research suggests that our primate relatives also possess this ability.

Scientists have discovered that both bonobos and chimpanzees are able to remember individuals they have previously interacted with, even after being apart for many years. Additionally, it seems that the strength of their previous relationship plays a role in this recognition.

Dr. Laura Lewis, a researcher at the University of California, Berkeley, stated that the findings demonstrate some of the most extensive long-term memory observed in non-human animals. This study is also among the first to suggest that apes’ memories may be influenced by their social connections.

“It is unexpected because the duration and characteristics of this collective memory are comparable to our own individual long-term memory.”

Lewis stated that, before this discovery, the longest recorded memory among non-human animals belonged to dolphins. These mammals are capable of retaining the vocalizations of others for up to 20 years. Additionally, bonobos have been observed to remember the vocalizations of past group members for a maximum of five and a half years.

In their publication in the Proceedings of the National Academy of Sciences, Lewis and his team detailed how they uncovered their findings by presenting images of other bonobos and chimpanzees to a group of 26 individuals from each species.

During the experiment, the group of apes were presented with two images simultaneously. One image featured a new individual that they had not encountered before, while the other showed a former group member who had either passed away or relocated at least nine months earlier. The team monitored the apes’ eye movements throughout the study.

The findings indicate that, on average, the apes took more time to view images of their previous group members compared to unfamiliar individuals. However, this trend was strongest among the 12 apes at Kumamoto sanctuary in Japan, who are more familiar with eye-tracking experiments on screens.

“During the study, it was found that bonobo named Louise had not been in contact with her sister Loretta or nephew Erin for more than 26 years. Surprisingly, she demonstrated a strong focus and preference towards both Loretta and Erin.”

The findings also indicate that the primates observed their previous group members for a longer period of time if their relationship was mostly positive, as opposed to negative.

Lewis stated that apes have positive relationships with others, which involve spending a significant amount of time in close proximity and grooming each other. This suggests that these relationships remain important to apes, even after being separated for extended periods of time.

Lewis stated that more research is needed to comprehend the reasons behind the potential evolutionary advantages of this type of long-term memory in apes. One possible factor could be that when female apes reach the age to reproduce, they tend to leave their birth groups and join neighboring groups as a means of avoiding inbreeding.

According to Lewis, it is possible that possessing long-term memory for others can assist in social situations where individuals are not in regular contact with each other.

Another researcher involved in the study, Dr. Christopher Krupenye from Johns Hopkins University, noted that the results indicated that apes have equal abilities in remembering both relatives and non-relatives. However, this could be due to the size of the sample or the significance of relationships beyond just family, as evidenced by strong bonds and alliances among non-relatives.

Having a comprehensive understanding of your social environment is crucial, regardless of familial relations, according to the speaker.

Source: theguardian.com