Friday, January 14, 2011

Brains

On this scruffy little sandstone island the largest animal other than humans is the domesticated goat. Wild animals? The Bahamian boa is the biggest. Rats, of course. Altogether a rather impoverished fauna.

But as I sit in the hammock chair on the screened porch there's lots of activity to watch. Hummingbirds at the hanging feeder. Bananaquits at the sugar dish on M's gardening table. Geckos skittering on the stoop. Occasionally a brown racer snake slips close to the house. I watch with a dreamy awareness.

The creatures are also aware of me, and quick to react if I startle them or move toward their space. To me, they are a source of entertainment and wonder. To them, I am a potential threat.

I rhapsodize. They react.

In her wonderful book The Sacred Depths of Nature, the biologist Ursula Goodenough reproduces a comparative diagram of vertebrate brains: codfish, frog, alligator, goose, cat, human. We all have pretty much the same inventory of parts. During the course of evolution, the hindbrain has undergone the fewest changes. The most significant development has been the steady increase in the relative and absolute size of the cerebrum, with a corresponding decrease in the importance of the midbrain. As I look at the diagram on the page, it's like watching an explosion of pink flesh as the cerebrum grows and folds until finally all those bulbs and lobes I share with the bananaquits and geckos are squeezed into a knot that looks a bit like an afterthought -- which is exactly the wrong word to describe them.

It's not that I have less hardwired functionality than the creatures outside the porch; parts of my brain maintain my breathing, balance and other activities I don't have to consciously think about, and I will startle as quickly as the hummingbird. It’s the plasticity of the human brain -- its ability to be programmed by experience -- that sets me apart, that lets me be aware of the creatures in a reflective, creative way, and even lets me be aware of my awareness.

The bananaquit's brain is the size of a pea; mine is the size of a softball. But I love the fact that we share the same essential design -- cerebellum, optic lobe, pituitary, olfactory bulb, cerebrum, etc. -- love the fact that we are bound together by the great and beautiful drama of evolution.

Sacred depths indeed!