During a late-night lab conversation, I came up with something that interests me. My view of how "intelligence" works is essentially reductive. The model I propose relies on selection. If what we call intelligence arises from the same dynamics as natural selection, then to me that means the "intelligent design" argument falls apart at the level of theory. I mean, among other reasons to doubt ID. Here I spell out the idea and ask you folks to assess whether it's a good argument or not.
Background (sorry of this seems pedantic, just trying to be clear for nonscientists): brain activity arises primarily from specialized, highly interconnected cells (neurons). They receive input from other neurons. Some might be stimulatory, some inhibitory. If the wiring of a neuron weights all inputs in favor of stimulation, it propagates a signal. Otherwise not. In this sense, a neuron can be thought of as a transistor or signal processor. Memories, thoughts and other activities might(I think probably) derive from larger or smaller sets of circuits of such linked sets of neurons.
I'll start with a very brief take on how I think intelligence arises. There's a lot more detail that we can flesh out in comments, but here's the basic gist.
First, memories. Say a parent dies. Information is received that is of huge emotional significance. The process of receiving that info can be distinguished from how it's weighted. For instance. Someone tells you your mother has passed away. There's, I dunno, an old familiar lamp and its light bulb suddenly dies with a pop. You store that information in a circuit, but weight it according to what you're feeling. Next time a light blows, you return to that moment. I'd argue that this is an emotional burden that has provided selective advantages. That's because although correlation doesn't necessarily imply causality, causality always implies correlation. In other words, if you see a stick that looks like a snake, it costs you less to pointlessly jump away than if you don't jump away when you see a snake that looks like it might be a curvy stick. This category of false-positives costs less in terms of survival than selecting for false-negatives. Returning to the light bulb. Your mind is geared, I argue, to link any event of strong emotional significance because not to do so is more costly than doing it. An unfortunate and extreme consequence of such selection algebra is probably PTSD.
Next: rewarding thoughts. There are pleasure centers in your brain. Their role (I think) is to amplify circuits that meet various criteria. Those criteria have presumably been selected by evolution. So. You want to fix your TV, right? You screw around with various things until, finally, you reason out a potential problem, test it and - eureka! - you fixed it! How do you feel? Pretty good. As a result, you'll remember how you got to the solution and what the solution was. That is, both the process by which you arrived at a rewarding answer and what the answer was that gave you a reward (Ethel! I fixed the TV all by myself!). To me that means that the neural circuits engaged in reasoning become reinforced by pleasure centers.
One more thing (bear with me). Years ago I figured that a significant advance in human evolution was the availability of what I call the "mental chalkboard". I'm almost certainly not the first to have thought of this, but haven't seen it elsewhere yet. The idea is this. By expanding the frontal (associative) cortex, the larger human brain gained the ability to represent reality to itself and compare that representation to learned experience. In so doing, the brain gained an enormous efficiency. Instead of having to traverse long distances to hunt, one could instead draw from experience to model what might be found on various routes. Virtual modeling is pretty much always more efficient than building/acting, provided that the model is accurate. We have the brain real estate to do that.
Here's the crux. Neural circuits are selected by evolution to "seek" solutions by representing various scenarios and comparing them to experience. The "method" circuits (gee, what if I tweak this knob?) and the "result" circuits (light bulb, or Ethel!) are both reinforced bypleasure/pain centers that evaluate the merits of a particular circuit against external reality. This is selection. Thoughts or circuits are selected based on their usefulness (evaluated by pleasure-center gatekeepers).
If this is an accurate but crude sketch of how intelligence works, then what does "intelligent design" actually mean? It means one process (natural selection) generated another process (intelligence) that in turn leads to useful outcomes or creations. Intelligence generates weapons/farming/buildings/language/nanotech/democracy to maximize its own survival.
Bottom line? Intelligence is a process arising from selection, both in its history and in how it acts. Intelligence then "designs" stuff in the real world to benefit itself. If the structure and mechanism of the "designer" can arise due to selection, where's the contrast? Selection is the deep mechanism in all cases.
btw, this gets really weird if you start asking the implicit questions. Are we really just matter organized by selection to "think"? Does that mean all complex systems are intelligent in some way? If some differently-defined concept of thought is intrinsic to any complex system, what does death actually represent? Just saying.
[update: I saw today a different formulation of the same argument, by Richard Dawkins(sixth paragraph).]