Bonobos' eyesight deteriorates as they age

KYOTO, Japan, Nov. 7 (UPI) -- The deterioration of eyesight over time isn't solely a human phenomenon. As new research revealed, bonobos become increasingly far-sighted as they get older.

Scientists determined each bonobo's vision health by measuring how far away they hold their arms from their face when grooming another ape. Just as an elderly human might hold the newspaper farther away to read the print, elderly chimps must move their eyes farther from their target to achieve proper focus.

"We found that wild bonobos showed the symptoms of long-sightedness around 40 years old," Heungjin Ryu, a scientist at the Primate Research Institute of Kyoto University, explained in a news release. "We were surprised that the pattern found in bonobos is strikingly similar to the pattern of modern humans."

Scientists photographed 14 wild bonobos in the Congo, measuring the grooming distance between partners ranging from 11 to 45 years old. The results showed grooming distance increases exponentially with age.

The findings -- detailed in the journal Current Biology -- suggest the deterioration of sight among humans has a natural evolutionary antecedent, undermining hypothesis that a lifetime of reading text and staring at screens is to blame for failing eyes.

"This suggests that senescence of the eyes has not changed much from the Pan-Homo common ancestor, even though the longevity of modern humans is far longer than that of chimpanzees and bonobos," concluded Ryu.