In our last episode, we were contemplating the wondrously efficient neural system by which reptiles managed to store learned information by reducing it to its most critical components and storing these as emotional reactions. The system seemed to work so well that the dinosaurs never bothered to change it. Silly dinosaurs! Then along came an asteroid and sat down beside them and blew those dinosaurs away. At this point, the mammals, losers and wimps that they were, took center stage. Along with various special traits, the mammals brought one special new idea to life's party: bigger brains with a completely new conceptual approach to processing: sequential thinking.
It's difficult for me to articulate just how tricky and special sequential thinking really is. We take it for granted, and love to disparage it as "linear thinking", but in fact sequential thinking is tricky business. I first sensed this when I began playing with digital electronics some twenty years ago. It was trivially simple to set up circuits that could handle direct stimulus-response relationships; you just slapped some gates together in whatever complicated pattern you desired. Yes, it could get pretty complicated, but in design terms it was easy to understand. Then came the day when I tried to design a circuit that would process a sequence of bits coming down a wire. All of a sudden life became vastly more complicated, because the circuit loses its instantaneous stimulus-response nature. You have to define a starting point for the sequence. Then you have to collect the first bit of information. Then you have to store it. Then you have to wait for the next bit of information. How long should you wait? How do you decide when you've waited too long? What if the second bit of information comes in fast, but the third comes in slowly, and the fourth comes in fast? How do you handle such complexities? Meanwhile, you've got to store all the incoming information in a convenient place, then bring it back out when it has been assembled. From this point, things get simpler: once the information is all lined up properly, processing it is just a straightforward pattern recognition issue. But getting it lined up in the first place is the trick.
Fortunately, this system can be built on top of existing pattern recognition neural circuitry. In other words, you can start with a conventional reptilian pattern-recognizing brain and add just a little bit of sequentializing circuitry, and all that sequentializing circuitry has to do is line up a temporal sequence of information into a spatial pattern, and then hand the pattern off to the regular pattern-recognizing circuitry. With just that tiny incremental improvement on the reptilian brain, all sorts of new behaviors become possible. For example, suppose that I am a small wimpy mammal and a big nastry predator lunges at me. If I had nothing but direct pattern-recognizing circuitry, I'd have a tough time escaping, but with just a little sequential-processing capabilities, I have a big advantage: I can process momentum. Suppose that he's on the left side of my visual field and I note that he is moving fast towards the right side of my visual field. By comparing the information on his previous position (left side) with his current position (right side), I can infer that he has lots of momentum towards the right -- so if I zag to the left, I can probably shake him. The reasoning process need not be so academic, but the trick does hinge on my ability to compare past information with current information: sequential information processing.
Well, if a little is good, then more must be better, right? That's what natural selection seemed to tell the mammals, because they started growing larger cortexes with greater sequential-processing capabilities. Most mammals can remember route information, taking circuitous paths around obstacles to reach their destinations; this is an example of more complex sequential thinking. Then the mammalian predators really pushed the envelope even further, inventing the concept of the hunt as a complex sequence of steps culminating in dinner. If you have any doubts as to the ability of mammals to engage in sequential thinking, just watch a cat stalk and capture its prey sometime. There's some pretty complicated sequential thinking going on in that furry head. Even more fascinating is the complex interaction between mammalian predator and mammalian prey. From stalking and evasion to the chase, the process is loaded with complex mental twists and turns as each tries to anticipate the opponent's move and counter it.
Then came the primates, and they apparently decided to invest a higher percentage of their biological capital into even bigger brains. This gave them the capacity for more complex social structures than any of the other mammals had, which in turn gave them a competitive advantage. With the hominids, we saw the first evidence of tool use. Pause for a moment to consider how utterly alien toolmaking is to pattern-recognition. It's not as if you can look at a chunk of flint and see cleanly scraped animal hides incipient in it. You have to think in a long, long sequence about how you could chip the flint to make it sharp, then carry the flint to a freshly killed animal, then use the flint to scrape the meat off the hide. Moreover, you must anticipate doing this many times, for the very essence of a tool is something whose capital cost to create exceeds the return from a single usage. This is highly sequential thinking!
Well, the cortex that handles all this sequential thinking just kept growing and growing, allowing more and more complex sequential thinking. Indeed, the growth of the human cortex over the last three million years can best be described as an explosion. It happened so fast that we just didn't have the time to adjust to it. Look how the female pelvis has been rearranged to get that big fat head out of the womb at birth -- what a pain! Human females don't walk, they kind of galumph along. High-heeled shoes are sexy because they accentuate the natural ungainliness of the female gait, which in turn is the direct result of our big heads. If we had small heads, high-heeled shoes wouldn't be sexy. Therefore, if you're female and are abducted by aliens, and they have really big heads (as aliens are wont to do), just put on some high-heeled shoes to drive them into a sexual frenzy and -- on second thought, maybe that wouldn't be such a good idea.
I realize all this stuff must sound deadly boring and academic, but I'll ask you to bear with me a while longer; there really is a point at the end of this excursion.