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The Problem with “Bad Design” Arguments

The past weekend’s Wall Street Journal offered an interview, “Cracking the Code of Life — at Light Speed,” featuring scientist Mike Hunkapiller who collaborated in inventing the first DNA-sequencing machines in the 1980s. Since Hunkapiller’s original sequencing machines, technology has made technical leaps and bounds, allowing large-scale sequencing projects targeted to divining the genomes of thousands of arthropods, birds, and vertebrates. Even though there has been much hype since, promising that diagnoses and cures for genetic diseases and various forms of cancer are just around the corner, the magical cures are regrettably still a few decades into the future. The interview is worth reading for insights into the ongoing work of one of the pioneers of the field.

Equally interesting are some of the debates in the Comments section of the article. One commenter noted how spineless politicians are, because they don’t provide more funding for genomic research that would allow scientists such as Hunkapiller to diagnose and cure diseases much faster. There was a reply from another reader who lamented that “so many in Washington are controlled by dark-ages [sic] beliefs.”

The response to that was issued by a woman who made a bold proclamation of her Christian faith, sensing where the previous poster was going with his comment. She continued with the argument that “natural selection does not rule out a designer.” Immediately after, a commenter called William Butler launched into a typical “bad design” argument. He asserted that the “designer” must be an “absolute idiot” or had some diabolical plan to “cause misery and cover his/her/its tracks” (whatever that means since a designer doesn’t have to answer to Butler or anyone else).

One of Butler’s arguments focused on the supposedly poor design of the eye, which is hardly an original argument. As I read his posts, it was apparent his knowledge only extended to maybe reading of a book or two by Richard Dawkins and I suspect some blog posts. His basic argument, as I expected, was that even though the eye is “remarkably good,” it is backwards and also “absolutely stupid” because light has to travel through blood vessels before reaching the light-sensing receptors. Thus, according to Butler, you end up with a blind spot. This is not a problem, he notes, for the camera eye of a cephalopod whose light-sensing cells point toward the incoming light, providing what he felt was a more “rational design.” Therefore, he posits, there cannot have been a designer of the human eye, since this is exactly what we would expect from natural selection.

I thought I would chime in to provide Mr. Butler a little education on the human eye, as, fortunately, Discovery Institute biologist Jonathan Wells has covered this beautifully in his latest book Zombie Science: More Icons of Evolution. Wells also recently wrote a succinct version of his argument at Evolution News asking, “Is the Human Eye Really Evidence Against Intelligent Design?” Thus armed, I was able to quickly rebut Butler’s arguments, and as of this writing, he hasn’t responded further.

Referencing Wells and the research he cites, I pointed out that the inverted retina actually provides higher optical quality than the cephalopod eye. The light-sensing rods and cones of the vertebrate eye operate at the highest metabolic rate of any tissue in the human body, with enormous energy requirements to continually regenerate themselves. A hefty blood supply is needed, which is provided by a dense network of capillaries that would block almost all incoming light. Since nerve cells in front of the rods and cones are relatively transparent, they block little of this light and thus the rods and cones can be located behind them. This allows for sustained higher metabolic activity relative to that of non-inverted eyes. The Wikipedia article on the evolution of the eye acknowledges this very thing (in the “Evolutionary baggage” section, no less).

As to the blind spot Butler speaks of, your average human with two good eyes doesn’t have to worry about a blind spot since they are in different places in each eye. Each eye covers the blind spot of the other eye, so the field of vision is unhindered. Moreover, the blind spot is in reality so small as to be unnoticeable even when you put your hand over one eye. There are simple tests you can do to find your blind spots. But unless you are specifically “looking” for them, you most likely won’t find them. So the blind-spot argument holds little weight, and is fully accounted for in vertebrates, all of whom normally have two eyes.

Another problem with Butler’s argument is built into his very assertion that the cephalopod eye is superior to the vertebrate eye. If the designer of the vertebrate is an “idiot” as Butler charges, then assuming there is a designer, how does Butler account for the fine design work of the cephalopod eye? Perhaps the designer is not quite the “idiot” that Butler thinks.

The problem with “bad design” arguments is that they flow from a rigid position of metaphysical naturalism, which, for problems of explaining biological complexity and its origins, permits Darwinian evolution as the only possible solution. Such arguments criticize the vertebrate eye, but in the same breath make a comparison to the cephalopod eye as if that was designed the right way. If that is the case, then why won’t the cephalopod eye demonstrate design, where each of these eye types, along with the compound eyes of arthropods, has a specific plan suited to the requirements of their respective organisms?

In a physical world there will be design constraints, so it is only realistic to expect tradeoffs. Nonetheless, there is no optical device devised by man that can match any eye type, so a little humility is appropriate. In fact, it is estimated that to build an optical device that can approximate the human eye, it would cost about $35 million and the thing would weigh around four tons. Yet each human has two completely gratis, weighing in at just 7.5 grams each!

Of course there are better eyes than ours. An eagle’s eye has vision that is four to five times better than the human eye. And then there is the peregrine falcon, equipped with special nictitating membranes (third eyelids) that allows high-speed dives from great heights at over 200 mph in order to catch prey. Hardly the work of an idiot designer, and virtually impossible by Darwinian natural selection and random mutation.

Photo: A peregrine falcon, by Alex Proimos [CC BY 2.0], via Wikimedia Commons.

Source: Evolution News