PZ Myers links to a great Ted Rall cartoon on Stupid Design. The point being that the world around us isn't anything close to being efficiently designed. If it is the reflection of the plans of some supernatural architect, many of us could have offered a few useful pointers. As with most such arguments, David Hume was there first:
In a word, Cleanthes, a man who follows your hypothesis is able perhaps to assert, or conjecture, that the universe, sometime, arose from something like design: but beyond that position he cannot ascertain one single circumstance; and is left afterwards to fix every point of his theology by the utmost license of fancy and hypothesis. This world, for aught he knows, is very faulty and imperfect, compared to a superior standard; and was only the first rude essay of some infant deity, who afterwards abandoned it, ashamed of his lame performance: it is the work only of some dependent, inferior deity; and is the object of derision to his superiors: it is the production of old age and dotage in some superannuated deity; and ever since his death, has run on at adventures, from the first impulse and active force which it received from him.
Hume gets extra bonus points for writing before Darwin demonstrated how complex adaptive organisms can arise even without a designer. (But he loses some points for weaseling at the end of the Dialogues.) Before Darwin, you couldn't really fault someone for thinking "Gee, my two choices are between imagining that something as complicated as a human being just sort of came together by accident, or that someone designed it. I think I'll go for Door Number Two." But once we figured out that there was a Door Number Three -- that such complexity could evolve through descent with random modification and natural selection -- it boggles the mind how anyone could look at the natural world and conclude that it shows any signs of being intentionally constructed just this way. One of the prevalent misconceptions about evolution is that, in response to a certain problem, organisms can (over the course of generations) simply "evolve an appropriate solution." Of course they don't always do so; sometimes they just die off. But more importantly, the space of possibilities that organisms explore via descent with minor modifications is most definitely not the space of small variations on bodies (or behaviors); it's the space of small variations on genomes. Even if a certain physiological feature would be useful, we're not going to be able to evolve it unless flicking a few switches in the genetic code would lead to an intrinsically useful mutation that would move us along that direction. Years ago, Stephen Jay Gould and Richard Lewontin borrowed the term spandrel from architecture to illustrate an important consequence of the way evolution works. A spandrel is an aspect of some form (whether from Renaissance arches or paedomorphic morphology) that arises as a side effect of some other trait that is useful, even if it doesn't itself serve a necessary purpose. Those kinds of non-adaptations and accidents and anachronistic features are found all over the place in real organisms. Any intelligent designer with a shred of self-respect would be embarrassed to exhibit such shoddy workmanship. The classic argument-from-design question is: What good is half an eye? Even when I was twelve years old, I could guess the answer to that one: it's a lot of good! Imagine just a few photo-sensitive cells evolving on the skin of a sightless organism; that could be immensely useful, offering a decided advantage to its offspring. Continual reinforcement of that tendency could directly lead to better sensitivity and all the other highly-specialized upgrades that our own eyes come with. On the other hand: What good is half a wheel? Now you've got me. The wheel is an excellent answer to a pretty obvious question, if you're a person sitting there thinking about how to move heavy loads more quickly or efficiently. And it's not hard to imagine wheels coming in useful on certain organisms. (Tell me that a snake with wheels wouldn't be pretty efficient, if a bit scary.) But you just can't get there from here, by ordinary evolutionary means. It's hard to think of useful transitional forms. All of which should teach us a lesson when we sit down to try to understand and reproduce the workings of actual organisms. The idea behind Strong Artificial Intelligence is that the brain is basically a computer -- a thesis I'm happy to go along with. But reproducing brainlike behavior in actual computers has turned out to be much harder than many people anticipated. In retrospect it's not hard to see why; the brain might be a computer, but it's certainly not the same kind of computer that we are used to programming. Its functioning arose naturally, rather than through top-down planning, and this kind of "organic design" leads to very different structures than "synthetic design." Rather than relatively straightforward sets of algorithms expressed in neurological lines of code divided into tidy subprograms, our minds are subtle machines with virtual processors distributed holographically and interacting nonlocally throughout the brain. As a result, computers still aren't very good poets, but they're definitely better at multiplication and division than we are. (Now you tell me which talent might have been more useful out there on the veldt.)
