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Ask Marilyn: Evolution and Poor Eyesite

William A. of Irvine, California, writes:

Marilyn: So many young people are nearsighted and need glasses. Why didn’t evolution select against poor eyesight?

Marilyn responds:

Myopia (nearsightedness) isn’t simply inherited. Evidence strongly suggests that only the tendency to develop myopia is inherited and that its actual development is mostly due to the ways in which a growing child uses his or her eyes.

In other words, the developing eyes respond to the needs of the child who uses them. If the eyes are used frequently for close visual activity, like reading or computer work, the child may be more likely to become myopic. So the stereotype of the bookish child who wears glasses may be rooted in truth. Today, add video gamers and other technology addicts to the list of young ­people affected

Some individuals are more susceptible than others, and if one or both parents are nearsighted, their children are more likely to develop myopia. Yet studies indicate that many children not just a small fraction—are born with the tendency. In nature, this kind of visual adaptability to one’s environment could be a positive trait. In civilization, however, we just wind up wearing glasses.


Scott Welch of Wilton, California, writes:

Marilyn: What is it about baby animals—and baby humans—that makes everyone think they’re so cute?

Marilyn responds:

Human babies are so helpless, so needy, so demanding and for so long!that without the development of a wildly positive emotional response from a parent, the species wouldn’t have evolved the way it did. That love of anything that shares the look of a human baby is what we feel when we describe something as “cute.” The features include large, forward-facing eyes set low in a roundish face, accompanied by small noses and mouths and rounded ears. Add floppy arms and legs, a side-to-side seesawing gait, cluelessness, and presto: It’s adorable! The young of dogs and cats and other mammals possess many of these traits to some degree, so we think they’re cute, too. Baby birds make the cutoff—barely—but baby reptiles and insects? Forget about it!


 
 
 
 

 

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