A 50-year-old woman seated in a dimly lit restaurant opens a menu, looks at it up close, then holds it at arm's length and reaches for her reading glasses. There's a solid reason this behavior is so common as we age: presbyopia.
The older people get, the harder it is to focus on details up close. The lens of the eye, which starts out soft and flexible, becomes thick and stiff with age. With this loss of lens elasticity, the eye struggles to focus on objects that are near. Part of the difficulty stems from the eye's increasing inability to focus light on the retina. Instead, the eye dials in the light in a different way, focusing light behind the retina. This condition, presbyopia, blurs a person's vision while they read printed materials or view the screen of a computer, tablet or smartphone.
But surely these vision issues are aggravated by the electronic milieu of modern life, right? All our up-close screen time must make this a purely human affliction. Well, not so fast. It turns out that wild bonobos (Pan paniscus) become farsighted as they age, too.
Researchers at Japan's Kyoto University have studied the bonobo — a close relative of the chimpanzee — in Japan's Luo Scientific Reserve for more than four decades. Much of that time, they observed bonobos in close contact with each other, getting close and personal to pick off bits of dirt and parasites. As time passed, though, the researchers realized they were seeing a markedly different behavior in the older bonobos, as these grooming rituals began to take place at arm's length.
The new study, published in the journal Current Biology, found that by age 35 the distance between bonobo grooming partners started to widen, from 4.69 inches (11.9 centimeters) to about 6.65 inches (16.9 centimeters). And by age 45, the partners were five times farther away from each other than younger pairs — an increase in distance attributed to age-related vision changes brought on by presbyopia.
The realization that people aren't the only ones in the animal kingdom dealing with vision issues as they age is intriguing, especially considering the bonobo shares more than 98 percent of its genetic profile with people. Looks like we're all in this together.