Argument from Undesign
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[edit] Introduction
There are a number of features of organisms that appear inept and foolish on the hypothesis that they were designed, but which are readily explicable in evolutionary terms; these provide evidence that organisms were in fact produced by evolution and not directly by the miraculous activity of an omniscient God.
This observation might be called the "argument from undesign", a phrase coined by the popular Christian apologist C. S. Lewis.
[edit] Examples
We shall give a selection of examples here: many others are known.
[edit] The recurrent laryngeal nerves
The recurrent laryngeal nerves in land vertebrates are a commonly given example of undesign. To connect the brain to the larynx, they take a circuitous route down the neck, through the thorax, wrapping around the arch of the aorta (in the case of the left recurrent laryngeal nerve) and the right subclavian artery (in the case of the right recurrent laryngeal nerve) before passing back up the neck to the larynx. This is costly in terms of the production of nerve fiber, and delays the nerve signals: considered as a piece of engineering, this is wasteful and pointless.
From an evolutionary perspective, however, it makes perfect sense: in fish, ancestral to land vertebrates, the homologous nerves are following a direct route: it is adaptation of the body plan of fish to that of terrestrial vertebrates that has left the nerves with this bizarrely circuitous route. Evolution, which proceeds in small adaptive steps, cannot simply unhook the nerves and rewire them from scratch, so we're stuck with it.
[edit] The blind spot
The blind spot in vertebrates is another commonly given example of undesign. the nerves leading from the light-sensitive cells emerge from the front of these cells and so have to pass through the retina to get to the brain, giving us a blind spot. Our brain fools us into ignoring this by filling in our visual field with what it thinks should be in the blind spot, based on the contents of the visual field surrounding the spot: to demonstrate that you do, in fact, have a blind spot, see this website.
This is, obviously, bad design; we can see that it is unnecessary by comparing it with the eyes of molluscs such as squid and octopods, which have the nerve fibers emerging from the back of the light-sensitive cells, and so have no blind spot.
From an evolutionary perspective, however, it makes perfect sense. The evolution of the eye is well-understood: it begins with a scattering of light-sensitive cells which do not function as a true eye, but merely distinguish light from darkness. At this point, it doesn't matter which way the nerves emerge from the cells: it is only in the later stages of eye evolution, when many light-sensitive cells are packed together densely to form a retina, that the way the nerves are connected becomes a problem.
As with the recurrent laryngeal nerves, evolution can't simply scrap the old design in favor of a new one: it works by progressive adaptation, and it is not possible to gradually turn the retina inside out in such a way that the intermediate stages would be favored by natural selection.
[edit] Non-functional DNA
Large swathes of DNA appear to have no particular function. This can be verified experimentally by removing it from the genome:
- A total of 2.3 million letters of DNA code from the 2.7-billion-base-pair mouse genome were deleted. To do this, embryonic cells were genetically engineered to contain the newly compact mouse genome. Mice were subsequently generated from these stem cells. The research team then compared the resulting mice with the abridged genome to mice with the full-length version. A variety of features were analysed, ranging from viability, growth and longevity to numerous other biochemical and molecular features. Despite the researchers' efforts to detect differences in the mice with the abridged genome, none were found.[1]
Where direct experimental evidence is not available, we may still infer the existence of non-functional DNA: for example, the single-celled organism Amoeba dubia has a genome 200 times the size of the human genome[2]; it is reasonable to infer that it doesn't really need that much.
From an evolutionary perspective, such sequences can be explained as selfish DNA. But its existence cannot be considered good design: it has costs but brings no benefits.
[edit] Quirks of embryology
There are a number of embryological quirks which similarly have a cost but no function. To take just one example, embryonic baleen whales produce, then lose, their teeth (baleen whales are toothless). These teeth are obviously of no use to an embryo in the womb.
An evolutionary rationale for this and similar features of embryological development can be found in our article on embryology and evolution. But it can hardly be considered good design, since it has costs but no benefits.
[edit] The "mysterious ways" excuse
The stock creationist answer to such conundrums is to explain that God's ways are not our ways, and that what seems stupid to us might seem like a good idea from his perspective, which is, of course, the right one.
But the result of this is to remove from the creationist hypothesis the only vestige of predictive power it ever had. For example, the theory of evolution predicts that fish should be streamlined; now, if we supposed that instead fish were produced in an act of fiat creation by a creator who designed things well by our criteria, then the creationist hypothesis would predict the same thing, and in this respect, if no other, would be as good as the theory of evolution.
But once we admit the "mysterious ways" excuse, then God might just as well have made fish shaped like bricks, for mysterious reasons known unto God but not vouchsafed unto men. Adding the "mysterious ways" excuse avoids the Argument From Undesign only at the cost of making the creationist hypothesis useless for its original purpose, i.e. to explain why, for the most part, organisms look well-designed.
Meanwhile the theory of evolution, as we have seen, can explain both the appearance of good "design" and the exceptions to it.
[edit] The creationist argument from undesign
Curiously enough, creationists have attempted to adopt the argument from undesign as an argument against evolution. They complain, for example, that evolution should have provided them with eyes in the back of their heads, infra-red vision, prehensile tails, and the like, as supposed improvements on the actual human form, and that their lack of these supposedly desirable traits proves that their bodies are not the products of evolution.
Now, any criticism of the natural world as imperfect would seem to be a better objection to the proposition that it was produced by a perfect creator than to the proposition that it was produced by the unintelligent, trial-and-error mechanisms of evolution. Any creationist who thinks that he should have a prehensile tail, you would think, should take up his complaint with the God whom he supposes to have created him.
At this point the "mysterious ways" excuse once more comes into play, as they explain that God's idea of what constitutes good design might be radically different from their idea of what good design is. However, they still maintain that evolution should have produced exactly what they conceive of as good design.
Each particular version of this argument needs to be assessed on its own lack of merit. However, we can point out some general classes into which creationist mistakes can be divided.
- Demanding the impossible. Some creationist complaints about nature are simply technically impossible to redress. For example, it is simply not energetically possible for an organism to evolve that subsists entirely by eating snow, as we have seen one creationist propose. Evolutionary processes cannot produce an organism that actually breaks the laws of nature. To take another example, we have seen another creationist insist that evolution should have given us the ability to detect infra-red, as a means of detecting potential predators and prey: but this would not work for warm-blooded organisms such as ourselves, since we would find that external sources of heat would be swamped by the heat of our own bodies; and we may note that all organisms that do have the faculty of detecting infra-red are cold-blooded.
- Failure to assess the cost/benefit ratio. Every part has a cost, in producing it, in maintaining it, and in the risk it presents of injury and infection. The benefits of, for example, a prehensile tail, are not that great for creatures such as ourselves, having hands with opposable thumbs which allow us to delicately manipulate objects held in front of us, where we can see them. All the animals we know of with prehensile tails are arboreal in habit and use the tails to cling more firmly to the branches of the trees in which they live.
- Failure to understand evolutionary processes. Let us assume for the sake of argument that eyes in the back of our heads would have a benefit greater than the associated cost. Nonetheless, it is hard to see how these extra eyes could evolve. For the evolution of the eye begins with light-sensitive cells that simply allow an organism to tell light from darkness. Now, the eyes we have allow us to do this. There would therefore be no selective advantage to the first step towards evolving extra eyes, and without a first step, there is no evolutionary pathway to the supposedly desirable final outcome of extra eyes. In the words of the old joke: "You can't get there from here".
Finally, we should note that there is something very strange about this whole argument in the mouths of creationists. These, after all, are the same people who go around pretending that evolution is about "random chance"; and that biologists explain the adaptation of organisms to their environment in terms of "pure coincidence"; and other such fatuous creationist lies. And yet when they find something in nature that they consider to be not absolutely perfect, they start talking as though evolutionary processes are omnipotent, omniscient, and omnibenevolent and so are guaranteed to produce their idea of perfection.
