An older bonobo (45 years old), grooms another with arms outstretched
Image: Heungjin Ryu (CC BY-NC 4.0)]
Written by Julia Cleghorn

While observing bonobos in the wild, researchers from Japan noticed an interesting and familiar behaviour. Older bonobos were grooming with their arms outstretched. While this might not sound particularly noteworthy, check it out in the picture here. Look familiar?

You might have seen your parents, or grandparents, do the same thing when reading the newspaper. They do this because their eyes have trouble focusing on things up close, known as long-sightedness.

When researchers noticed this behaviour in the wild bonobos of Wamba, Democratic Republic of the Congo, they hypothesised that bonobos, one of human’s closest primate relatives, were also losing their sight as they aged.

To find out more, they took digital photos of 14 wild bonobos, aged 11–45, while grooming. Then they measured the distance between the bonobos’ face and hands. The photos revealed that grooming distance increased exponentially with age.

“The progress of long-sightedness in bonobos was strikingly similar to that of humans,” says lead researcher, Heungjin Ryu, of his work at the Primate Research Institute at Kyoto University, Japan.

“We found that wild bonobos showed the symptoms of long-sightedness around 40 years old,” says Heungjin. This is the same age humans start to notice the condition. “It suggests that over six to seven million years … the aging of eyes might not have changed.”

So, our failing eyesight might not be the result of our modern day lives, staring at computer screens all day. It might actually be a natural trait dating back to a common ancestor!

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