Reposted from the old TfK because it's fun.
In KU's introductory biology lab about evolution, the students are asked (not my phrasing):
In the vertebrate animal clade, jaws have evolved from cartilage-like rods associated with gills. In jawless ancestral vertebrates, as well as extant jawless species such as hagfish and lampreys, the function of these skeletal rods was/is to support the gills. Jaws function to grasp and chew, their success is notable, as jaws are still present in most extant vertebrates. If an engineer were put to the task of designing "jaws," would the outcome be the same as the evolutionary outcome we observe in jawed vertebrates? Explain your reasoning.
I usually mention that the reptile jaw consists of three bones on each side, while the mammalian jaw has only one bone on each side. The other two bones migrated into the inner ear. We have fossils with an articulation on the third bone and another on the first, a perfect transition. "If you designed a jaw," I ask confused students, "would you start by making really good gills, then take the parts of that to build a jaw, then take some parts of that away and use them to build a microphone?"
They usually say that they wouldn't. The point is that even if the end result were identical to jaws we see now, the process that leads to the final product is very different. An engineer has a goal and works toward it. Evolution can see maybe half a step ahead, and really can only look backward. Whatever works, sticks, whatever doesn't work, dies out. The existing structures we see are dependent on historical contingency.
For really confused students, I draw on a point Stephen Jay Gould made in Eight Little Piggies (in the essay by the same name), that the number of fingers we have is entirely contingent on history. While one can try to construct an explanation for the superiority of 5 fingers, paleontological history shows that there were potential ancestors of the tetrapod clade (which we are part of) which had as many as eight rays per fin. If they had succeeded, 8 fingers would be the norm, and the Simpsons would look very odd with only 4. As Gould says of historical contingency: "Other configurations would have worked and might have evolved, but they didn't--and five works well enough."
In the essay, Gould is building on a point he made most forcefully in an essay he wrote with Richard Lewontin, "The Spandrels of San Marcos and the Panglossian Paradigm: A Critique of the Adaptationist Program." The point was that biologists were too quick to insist that every feature was adaptive and a result of natural selection. Spandrels are triangular structures produced when two round arches meet. They are necessary byproducts of joining rounded and flat surfaces. Nonetheless, in many churches they are richly decorated and the entire artistic vision for a space can be shaped by the spandrels. One might, Gould points out, be lead to think that the spandrels are there in order to be used for paintings, and not that they are necessary by-products nicely dressed up. The worldview he criticizes treats anything, whether spandrels or five fingers, as the product of intense selection, a perfect solution to the problems it faces.
an old argument holds that five [digits] might be an optimal configuration for weight-bearing--a central axis centered on digit three, with adequate and symmetrical buttressing on each side (one or three toes might not provide enough lateral support against wobbling, while seven toes might be superfluous and interfere with locomotion). On this argument, tetrapods have five toes because support and locomotion demand (or at least strongly encourage) this configuration as optimal.
Gould compared this approach to that of Voltaire's Doctor Pangloss, the court metaphysician in Candide: or Optimism.
Master Pangloss taught the metaphysico-theologo-cosmolonigology. He could prove to admiration that there is no effect without a cause; and, that in this best of all possible worlds, the Baron's castle was the most magnificent of all castles, and My Lady the best of all possible baronesses.
"It is demonstrable," said he, "that things cannot be otherwise than as they are; for as all things have been created for some end, they must necessarily be created for the best end. Observe, for instance, the nose is formed for spectacles, therefore we wear spectacles. The legs are visibly designed for stockings, accordingly we wear stockings. Stones were made to be hewn and to construct castles, therefore My Lord has a magnificent castle; for the greatest baron in the province ought to be the best lodged. Swine were intended to be eaten, therefore we eat pork all the year round: and they, who assert that everything is right, do not express themselves correctly; they should say that everything is best."
Later, when the good Doctor has contracted syphilis, he says:
it was a thing unavoidable, a necessary ingredient in the best of worlds; for if Columbus had not caught in an island in America this disease, which contaminates the source of generation, and frequently impedes propagation itself, and is evidently opposed to the great end of nature, we should have had neither chocolate nor cochineal.
I raise this for two reasons. The same spirit that moved Gould and Lewontin to decry this approach to the analysis of biological systems also moved people to crack down on "just-so stories," but to be clear about how a given hypothesis about a structure might be tested. The Index of Creationist Claims explains more. Creationists like to toss that word around now, but it was biologists who saw the problem and have fixed it.
Furthermore, modern creationism often takes on exactly this approach. The classic example is Privileged Planet, the book and movie which the Discovery Institute has been pushing as a case for Design in the Universe. The book is, so far as I've been able to determine, an extended Panglossian diatribe. Our moon is the best of all possible moons because its position is just-so. Our solar system, our planet, our galaxy, the galaxies around us, our atmosphere, our eyes, our mountains, our orbit, our sun, all is for the best in this best of all possible worlds.
The same approach creeps into creationism in its terrestrial focus. We know Noah was able to fit all those animals onto the ark because it was just-so. The rainbow is evidence enough. The earth is 6,000 years old because that's what you get when you add up all the generations in the Bible, and all the available scientific evidence says otherwise because things cannot be otherwise than they are. The flagellum is a perfect outboard motor, it cannot be otherwise than as it is, for as it has been created for some end, it must necessarily be created for the best end (the rear end of a bacterium). Humans, who surely did not descend from primates, cannot be other than we are. And so forth. Of course, Dembski insists that intelligent design need not be optimal design, but that's a dodge. Consider the end of his essay from February, 2000:
This is a fallen world. The good that God initially intended is no longer fully in evidence. Much has been perverted. Dysteleology, the perversion of design in nature, is a reality. It is evident all around us. But how do we explain it? The scientific naturalist explains dysteleology by claiming that the design in nature is only apparent, that it arose through mutation and natural selection (or some other natural mechanism), and that imperfection, cruelty, and waste are fully to be expected from such mechanisms. But such mechanisms cannot explain the complex, information-rich structures in nature that signal actual and not merely apparent design--that is, intelligent design.
The design in nature is actual. More often than we would like, that design has gotten perverted. But the perversion of design--dysteleology--is not explained by denying design, but by accepting it and meeting the problem of evil head on. The problem of evil is a theological problem. To force a resolution of the problem by reducing all design to apparent design is an evasion. It avoids both the scientific challenge posed by specified complexity, and it avoids the hard work of faith, whose job is to discern God's hand in creation despite the occlusions of evil.
The good that who initially intended? I thought we didn't know who the Designer is? Anyway.
The scientist doesn't try to "explain dysteleology." The scientist recognizes that issues of teleology are for theologians to handle, and focuses on the processes which lead to a given outcome.
IDolators want teleology. They want 4.55 billion years 6000 years 4.55 b 6000 history to be inevitably leading to them, right now. They want to live in a world where everything is best. Or at least could be, without those scientific naturalists mucking things up.
Voltaire concludes his tale of Optimism with this passage:
In the neighborhood lived a famous dervish who passed for the best philosopher in Turkey; they went to consult him: Pangloss, who was their spokesman, addressed him thus:
"Master, we come to entreat you to tell us why so strange an animal as man has been formed?"
"Why do you trouble your head about it?" said the dervish; "is it any business of yours?"
"But, Reverend Father," said Candide, "there is a horrible deal of evil on the earth."
"What signifies it," said the dervish, "whether there is evil or good? When His Highness sends a ship to Egypt does he trouble his head whether the rats in the vessel are at their ease or not?"
"What must then be done?" said Pangloss.
"Be silent," answered the dervish.
"I flattered myself," replied Pangloss, "to have reasoned a little with you on the causes and effects, on the best of possible worlds, the origin of evil, the nature of the soul, and a pre-established harmony."
At these words the dervish shut the door in their faces.
Adieu to the Panglossian creationists. There are more interesting questions in the world than why lower back pain is the most common form of chronic pain. The human back is vertical, all our ancestors have horizontal vertebral columns. However optimal the curve of our spine, it is not how an engineer would build a vertical support. It's exactly what you'd get if you took a lemur, stood it on two legs and didn't give it the good sense to lift with the knees, not with the back.
Incidentally, knees aren't so well designed. Bipedalism is novel within mammals, and we haven't worked all the kinks out. One could speculate on the great benefits this brings to orthopedic surgeons, but I'll close the door on that question for now.
The good that who initially intended?
I think what he meant to say was "the good that was intended by God to be initial." Because if the world is fallen then God must have intended that too, so the good would have only been intended to be initial. And then punish the whole human race.
Anyway, thanks for posting those couple of paragraphs of Mr. Dembski's gibberish. It is always a pleasure. Cheers.
I'm a bit confused about a few sentences from your post. You said,
"Evolution can see maybe half a step ahead, and really can only look backward. Whatever works, sticks, whatever doesn't work, dies out. The existing structures we see are dependent on historical contingency."
I don't understand the teleological notion of evolution "looking" either half steps forward or back. My conception of evolution has always been that of its being a consequence, not an apriori plan being refined by looking ahead and behind. I conceive of the current state of biodiversity as a direct consequence of the biodiversity of the immediately previous generation as acted on by mechanisms like selection, drift, etc.
Can you elucidate a bit the idea of evolution "looking?"
Then, too, I wondered about, "Whatever works, sticks, whatever doesn't work, dies out. The existing structures we see are dependent on historical contingency." In the first sentence I get the sense that you endorse a strict selectionist evolutionary model, while the second seems to contradict that notion.
Can you provide a slightly clearer view of how you picture evolution playing out?
Do you know if the NCSE has an evolution curriculum or study guide for independent scholars, autodidacts and the like? I've looked over their sight and I don't see anything like that. It would be a useful reference for those like myself who wish to bring ancient coursework up to date, and put it to use in public forums like Cafe Scientifique.
What I mean by "looking back" is that it is a contingent process dependent on the past state of the organism's ancestors, the past selective pressures they faced, and the random forces acting on them. As you observe, talking about this as "looking back" is a reification of "evolution" into a thing with its own volition, but is meant to contrast between teleology (directed toward something) and simple directionality. Evolutionary history can be traced backwards, but its future course is not pre-defined.
As for a study guide, I'd recommend Berkeley's Understanding Evolution as a good starting point. For something (substantially) more advanced, I've found West-Eberhard's Developmental Plasticity and Evolution to be a useful upper-level survey of some aspects of the current state of evolutionary biology. It's focussed on evo-devo, but I think it's as close as anyone's gotten to working through the implications of advances in developmental biology for studies of evolution broadly speaking.
If you're looking for something different, let me know and I'll poke around.
I'll give the material a close look and inquire further of you if need be.