|Toy tin robot in the show. Boston MA United States. Picture taken by Jonathan McIntosh, 2003; Wikimedia|
As I've gotten older, my vision has gotten worse, each eye in its own way. My eyes are equidistant from 20:20 in opposite directions, one myopic, the other hyperopic; I can still see without glasses, though not perfectly. And still, without my glasses, it's one eye working at a time.
|Vision pathway; Weiss and Buchanan, The Mermaid's Tale, 2009|
And at some point, in managing input anywhere along the continuum from my eyes to the furthest point I can see, my brain switches from paying attention to my right eye to paying attention to my left. All the light waves are getting passed along in the same way to both eyes and on to my visual cortex -- I know this because if I close the 'good' eye, of course I'm seeing something, it's just blurry -- but at the very final step in the vision pathway, when my visual cortex is coordinating all the input into a single image, my brain dumps the blurry images and retains the clear.
But it's even more impressive, I think -- with my glasses on, my brain allows input from both eyes to make its way to the final image. It's switching from monocular to binocular vision all the time. Again, how does it know to do that?
My eyes as a metaphor for life
The plasticity of the brain isn't confined to the vision pathway, of course. Plasticity defines the brain -- it's why we can meet new people, learn things, have new experiences, create memories, and then make sense of it all as we go. Not only are we constantly making new synapses between neurons, we are still making new neurons well into old age, which is what makes our brains able to successfully make sense of all the information with which we're bombarded all the time. Adaptability, or facultativeness, is so fundamental to evolutionary success that we think of it as a basic principle of life (see chapter 3, The Mermaid's Tale).
And yes, there's a larger point here. The idea that some of us evolved 'for' sprinting, ping-pong, money-lending, economic prowess, or the ability to do well in 20th century school systems is based on, we think, a superficial understanding of evolution, and the way the brain works. But it's an appealing one, one that too many scientists and journalists still believe.
Ideology assumes, science asks.