Only a mobile creature needs a brain, points out New York University neurophysiologist Rodolfo Llinias in his 2002 book, I of the Vortex: From Neurons to Self. To illustrate he uses the example of a tiny jellyfish-like animal called the sea squirt: Born with a simple spinal cord and a three hundred-neuron “brain,” the larva motors around in the shallows until it finds a nice patch of coral on which to put down its roots. It has about twelve hours to do so, or it will die. Once safely attached, however, the sea squirt simply eats its brain. For most of its life it looks more like a plant than an animal, and since it’s not moving, it has no use for its brain. Llinas’ interpretation: “That which we call thinking is the evolutionary internalization of movement.”
— Spark: The Revolutionary New Science of Exercise and the Brain, by John J. Ratey and Eric Hagerman
Suppose you already know the outcome of an otherwise difficult choice. Go left or go right. You already know that the left path leads astray into danger, and that the right path leads safely home. Would you bother thinking it over, analyzing the situation, debating your choice? Of course not. When there is no uncertainty, concrete action is preferable to talking and thinking. Thinking too much only causes anxiety; action clears it.
The absence of uncertainty is exceedingly rare. The universe is a story of things in motion. Once there was a high ordered singularity, then there was a big bang. Everything since is dissipation of energy, the expansion of the universe to entropy. Change is constant and the things that survive are the ones that can adapt to it. Brains are for managing change. Humans evolved brains with the ability to think, to analyze and evaluate, to rehearse and estimate, to predict and control. At the limit of our biological brains, we invented technologies to make us smarter yet. Pencils, pens, paper. Books, computers and artificial intelligence. Information technologies externalize and extend human brains.
Is it the universe that is endlessly complex or is it our minds? Was life simpler in the past? We think so, but each generation thinks its time the most complex. Twenty years you thought your life was complex. Complexity may be a constant. Perhaps it is only our minds that are in constant motion. Movement cannot fathom stillness. The only way for movement to be aware of stillness would be to stop, to turn upon itself with a small crunch, and, like the sea-squirt, eat its own brain.