In his review of Dawkins most recent book, Jerry Coyne writes:
Even more evidence for evolution comes from the “bad designs” of animals and plants, which, Dawkins observes, look nothing like de novo creations of an efficient celestial engineer. His favorite example–and mine–is the recurrent laryngeal nerve, which runs from the brain to the larynx. In mammals it doesn’t take the direct route (a matter of a few inches) but makes a curiously long detour, running from the head to the heart, looping around the aorta and then doubling back up to the neck. In the giraffe, this detour involves traversing that enormous neck twice–adding about fifteen feet of superfluous nerve. Anyone who’s dissected an animal in biology class will surely agree with Dawkins’s conclusion: “the overwhelming impression you get from surveying any part of the innards of a large animal is that it is a mess! Not only would a designer never have made a mistake like that nervous detour; a decent designer would never have perpetuated anything of the shambles that is the criss-crossing maze of arteries, veins, nerves, intestines, wads of fat and muscle, mesenteries and more.”
Creationists often object to this sort of argument, saying that it’s not scientific but theological. God is inscrutable, they claim, so how could we possibly know how he would or would not design creatures? But this misses the point, for the “bad design” we see is precisely what we’d expect if evolution were true. The laryngeal nerve takes that long detour because, in our fishy ancestors, it was lined up behind a blood vessel, with both nerve and vessel servicing the gills. As the artery moved backward during its evolution to the mammalian aorta, the nerve was constrained to move behind it, although its target (the larynx, an evolutionary descendant of the gill arch) remained up in the neck. If you insist that such designs reflect God’s plan, then you must admit that his plan was to make things look as if they had evolved.
There is some sleight of hand to detect here. Coyne/Dawkins begin with a “bad design” argument, but when confronted by the criticism that this argument is theological, they shift gears and insist they are really arguing that the mammalian nerve route is best understood by considering fish development and physiology. In other words, it’s just an argument for homology. And since arguments for homology do not depend on something that looks nothing like de novo creations of an efficient celestial engineer, the whole bad design argument is superfluous.
The problem with Coyne’s complaint is that it is coupled to a double standard. Bad design counts as evidence against design, but I doubt Coyne would acknowledge the other side of the coin – good design counts as evidence for design. From his non-teleological perspective, it is “heads I win, tails you lose.” Bad design counts against an intelligent design and good design counts as evidence for how good the designer mimic can be. All data are absorbed into the Duck.