Bonobos and chimpanzees possess the longest long-term memory among animals, according to a study by researchers from the University of California. These primates are capable of remembering relatives they interacted with in the past, even after decades of separation.
“The findings indicate the longest long-term memory ever recorded in animals. This is one of the first studies to demonstrate that monkeys’ memories are shaped by their social bonds,” said researcher Laura Lewis, as reported by The Guardian.
In the experiment, 26 bonobos and chimpanzees were shown photographs of their relatives. The animals were simultaneously presented with two images: one of a stranger and the other of a former group mate who had either passed away or had been moved at least nine months prior. The researchers recorded the direction of the animals' gaze and their reactions.
The results showed that, on average, the animals looked longer at images of familiar individuals, particularly highlighting those with whom they had previously had good relationships. The most impressive result was recorded for a bonobo named Louise, who recognized her sister and nephew 26 years after their separation.
The researchers noted that further experiments are needed to determine why this type of long-term memory has been supported by natural selection. However, they suggest that one reason may be that females typically leave their natal groups after reaching reproductive age to avoid inbreeding. The ability to retain images of relatives for a long time may be beneficial in such social conditions.
