Why do we have eyesight?

Why indeed? A quite interesting question!

Vision, arguably the most important of the 5 basic senses, is the most immediate but also the most sensitive to far-away origination. In the brain, neurons devoted to visual processing number in the hundreds of millions and take up about 30 percent of the cortex, as compared to 8 percent for touch and just 3 percent for hearing.

Since light is so very much faster than sound, we see the flash of a distant lightning strike long before we can hear it rumble. Although it depends on the type of nerve fiber, a bite to your foot will send neural impulse to your brain at a speed ranging from a sluggish 2 miles per hour to, in some myelinated fibers, 200 miles per hour. But even this top speed is 3 million times slower than the speed of light to your eye. And the brain can process that image of the snake hitting the retina in as little as 20 milliseconds!

Vision, then, is the most useful of the senses for survival. The advantage of using it would have given our genetic ur-ancestors a serious edge in surviving predators and finding food so as to mate and pass on our genes.

 

- Dr. Woodhams