July 8, 2012
Nature’s Brains, Part 2
(Note: I invite you to read Part 1 before you dive into this part.)
Nature is the Great Inventor. Through its innovative experiments we have an awe-inspiring array of species. Considering only the animal kingdom, there exists such a marvelous set of unexpected forms. Some, in fact, are altogether strange. Nature makes even the most creative Hollywood creature-maker look like an imbecile.
Among nature’s animals on this planet (both living and extinct), there is a notable subclass, namely, those creatures possessing a brain. Now, at the extreme, where we find insects, spiders, bugs, worm and snails, we might want to argue about what is the minimum level of neural tissue that actually qualifies as a brain. But that is not the motivating question behind this essay. So we will keep our focus on animals whose possession of a brain is undeniable.
Over the eons nature rolled many dice, so to speak, and out popped numerous experimental forms. Many of these species couldn’t cut it. Either these species failed to compete or to harmonize with other species in their neighborhoods and petered out. More likely it was not an either-or. These extinguished germ lines most likely failed to compete and to harmonize with other species. More about that, later.
However, somewhere in the succession of new forms, one innovation appeared that had lasting value: a brain. In order to continue this discussion, we must relieve ourselves of the conviction that human brains are the only ones worth considering. Or even that only mammalian brains merit discussion. Certainly there are many scientists—biologists, ethologists, geneticists, neurologists and bio-psychologists—for whom this widening of the field is a no-brainer. (I just made a funny. Huh.)
But to include the rest of us in on the discussion, let’s start by noticing that once nature chanced upon the brain as an animal trait, it was simply too valuable to relinquish. Animals with brains prospered, and the number of such species multiplied. Brains can be used in creatures that graze, hunt, swim, fly and burrow.
There is a little more to the story, though. Brains come at a cost. They must be encased for protection. They put demands on their owners for large amounts of oxygen, chemical energy (glucose), and other nutrients. As an organ, brains take longer to develop than other organs. Some animal experiments probably abandoned the concept (“It’s a luxury, not a requirement”) and chose a different reproductive strategy, such as laying a million eggs. But, seeing how many brains inhabit the directory of animals, I think we’re safe in concluding that brains established themselves in the genetic menu because of their lasting value. (Kind of like pizza and ice cream. I’m only kidding.)
Well, then, what exactly is a brain, one might ask? In questions of this sort, I usually start with the simplest definition I can imagine. A brain is a storage medium that can encode (store) a repertoire of behaviors and can allow the animal to apply them in the appropriate situations. With a brain, an animal can either store more types of behaviors and/or more complex behaviors.
As an aside, one of my favorite examples is the web-building spider. The spider web is a marvel of engineering. The spider can build one wherever it finds itself, using whatever objects happen to be present. If you look at many garden spiders in the city, you will find that they opportunistically choose a spot for a web because there is a nearby light that will attract flying insects. Even a streetlight three houses away will do. They don’t stop and check to see if there are precisely six branches and an overhang. They go ahead and use the available props. This is the height of creativity!
In spiders I see a tiny brain used to store one fairly complex behavior (web-building) and an assortment of quite simple ones (such as running for cover if a shadow moves over quickly).
So, just like the cellular telephone, brains found a stable niche because they proved to be a useful “natural technology” that was too valuable to give up. As a result, there ensued a lengthy series of design experiments to show what could be made from this basic concept.