A new study has revealed that bonobos, some of humanity’s closest relatives, suffer from similar eye problems in old age. This would seem to indicate that long-sightedness isn’t a problem of modern lifestyle, but something completely different.

This photo shows Fuku (female: 17 years old) grooming Hoshi (female: 32 years old). She needs only 5 to 10 centimeters between her fingers to eyes to get pin-focus for grooming. Credit: Heungjin Ryu (CC BY-NC 4.0)

Long-sightedness affects the ability to see nearby objects. You may see very well distantly, but closer objects can be out of focus — especially when reading or using a computer. While it can affect people of all ages, people over 40 years old are especially vulnerable to it. The modern lifestyle is often blamed for this condition.

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We spend too much time focusing our eyes on things which are close-by, we tire them working on computers and we don’t spend enough time in open spaces where our eyes can relax. But new studies have cast that theory into doubt by studying our closest relatives: chimps and bonobos. Previous studies have indicated that chimps also get long-sightedness in old age, and now, a new study has found the same thing in bonobos.

“One day, I was with another researcher and observed the oldest male bonobo Ten (TN) grooming Jeudi (JD),” Ryu recalls. “TN had to stretch his arm to groom JD, and only when he found something on JD’s body would he come close to remove it using his mouth. It was funny to see how he groomed.”

But while it may have been funny to them, it really is a struggle for bonobos and might have serious consequences for their survival. So scientists started studying exactly how their eyesight fares by using┬ádigital photographs to measure the grooming distance of 14 wild bonobos of various ages, ranging from 11 to 45 years old. The measurements showed that the distance increased exponentially with age — in other words, older bonobos groomed from further away, just like a human would hold the book a bit further away.

“The results we found were very surprising even for us,” Ryu says. “When I started to collect data, I did not expect that age could be such a strong predictor of long-sightedness.”

This also indicates that modern lifestyle isn’t to blame for the decline in our eyesight, or at least not entirely. There’s something else causing a decline in eyesight, a process deeply rooted in our evolutionary history.

Journal Reference: Heungjin Ryu, Kirsty E. Graham, Tetsuya Sakamaki, Takeshi Furuichi. Long-sightedness in old wild bonobos during grooming. Current Biology, November 2016 DOI: 10.1016/j.cub.2016.09.019 |