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Why the Argument from Suboptimal Design Is Weak

Jonathan McLatchie
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I recently received correspondence from a chess Grand Master I know. As an atheist, and an adherent of evolutionary orthodoxy, he wanted to know how I, an ID advocate, would respond to the problem of poor or suboptimal design in nature — an argument to which, he claimed, he had never encountered a satisfactory answer. He gave a few examples, “rang[ing] from technical design flaws such as the recurrent laryngeal nerve, to vestigial features such as the marsupial mole having non-functioning eyes hidden under its skin, to ‘commonsense’ features such as using the same mouth for both eating and breathing, leading to an untold number of deaths through choking.”

I responded by pointing out what seems to me to be four significant flaws in the argument from suboptimal design against ID. The first problem with the argument is that the ability to detect design does not require that the design be optimal. Microsoft Windows operating systems have many design flaws — but that does not make them any less designed. All it takes to show the unsoundness of the argument is for me to point to, as counter-examples, systems that we know are designed but that are, in fact, suboptimal. Plenty of such cases come to mind. The argument carries the assumption that the only candidate for designer is an omnipotent and benevolent deity, but this does not necessarily follow. I happen to believe in such a deity (for, in my judgment, good reasons), but I don’t believe that the evidence of design in biology demands it. Even if one is a theist, I see no problem with the position that God may have acted through secondary causes. Perhaps there is some sort of intrinsic teleology built into the world, for instance, that produces the sort of complex specified information we find so abundantly in living systems.

A second problem with the argument is that it assumes that an intelligent cause would have to produce each living thing de novo. But, again, this does not necessarily follow. The theory of ID (as applied to biology) asserts that there are certain features of living systems that bear hallmarks of an intelligent cause, but this does not necessarily entail a rejection of common ancestry. Perhaps there are constraints on design placed by an organism’s evolutionary history. I happen to be skeptical of universal common ancestry, for reasons that I have articulated in my writings here at ENV. But it isn’t at all incompatible with ID — in fact, many of my colleagues in the ID movement (for example, Michael Behe, Michael Denton) subscribe to common descent. I’m ambivalent. I can see some defensible arguments for the idea of hereditary continuity, but I can also see severe scientific problems with it. In my opinion, many evolutionary theorists on this point fall victim to confirmation bias.

Third, the theory of ID does not require that everything in biology be designed. Indeed, designed artifacts may exhibit evidence of weathering. An illustration would be the once-functional vestigial lenses of marsupial moles which are hidden under the skin.

Fourth, the argument often commits what one might describe as an “evolution-of-the-gaps” fallacy. Whereas the “god-of-the-gaps” fallacy states that “evolution can’t explain this; therefore god must have done it,” the converse “evolution-of-the-gaps” fallacy states that “God wouldn’t have done it that way; therefore evolution must have done it.” It is curious that this dichotomous mode of thinking is precisely what ID proponents are often accused of. Much like “god-of-the-gaps” arguments, the “evolution-of-the-gaps” argument has to retreat with advances in scientific knowledge, as biologists uncover important reasons for the way these features have been designed. One example of this would be the once-thought-to-be-prevalent “junk DNA” in our genomes, for which important function is constantly being identified. I would argue that such design reasons or “trade-offs” are plausible for the recurrent laryngeal nerve (as well as many of the other examples that are traditionally cited, such as the allegedly backwards wiring of the retina), as we have discussed extensively at ENV.

Shortly after making the above points, I received a response from my friend. Regarding my first three objections, my friend wrote (quoted with permission):

…you’re essentially saying you believe God is responsible for some but not necessarily all of the design features we see in the natural world — which effectively gives you a “Get Out of Jail Free” card for any example of poor design that a critic may throw at you, as you can simply reply, “I believe God created/designed some ancestor of that species, but then evolution took its course, which led to the occurrence of that particular design flaw.”

But this isn’t exactly what I was saying. First, ID (in its purest sense) is neutral on who the designer is. The theory of ID has two components — the design inference (our methods for detecting design) and the design hypothesis (the hypothesis that a certain feature is designed). Inferring design in nature does not require that one know the identity or nature of the designer. Moreover, I do not think it is unreasonable to assert that teleology and evolutionary mechanisms can work together — I believe that evolutionary mechanisms are grossly inadequate to account for the complexity of life (and demonstrably so), but they certainly do operate. If, for example, a mutation inactivates a gene (creating a unitary pseudogene) and this somehow becomes fixed (either through drift or because the inactivation of the gene confers some sort of survival advantage), one might consider this to be “suboptimal design.” But I don’t think this is really a compelling argument against the hypothesis of original design. The same is true with all so-called “vestigial organs” such as the human appendix. All of them involve the loss of traits, not their origination.

As for my fourth criticism of the argument, my friend wrote,

Regarding the “evolution of the gaps” argument, I’m not sure if you’re suggesting this applies to any of the examples I gave. Personally I don’t think of these examples as actively providing evidence for evolution — although in many cases they offer what I might think of as “circumstantial evidence,” e.g. the RLN being associated with our fishy ancestors (hardly a technical term but you know what I mean).

But such cases of “suboptimal design” are quite routinely given as evidence for common descent. Jerry Coyne has a whole chapter on it in his book Why Evolution is True (which I recently reviewed here). The recurrent laryngeal nerve is an interesting example, but there is reason to think there may well be design reasons for its circuitous route. I would say that the RLN could be taken as suggestive or circumstantial evidence for our shared ancestry with fish. But there is other evidence as well that needs to be taken into account, much of which militates against the idea of common ancestry. The RLN, then, while interesting, should not be considered in isolation from the other evidence.

Here’s the bottom line: The argument from suboptimal design in biology is weak, since it can be defeated by pointing to counter-examples of suboptimally engineered systems (of which there are many) that we know are nonetheless intelligently designed.

Jonathan McLatchie

Fellow, Center for Science and Culture
Dr. Jonathan McLatchie holds a Bachelor's degree in Forensic Biology from the University of Strathclyde, a Masters (M.Res) degree in Evolutionary Biology from the University of Glasgow, a second Master's degree in Medical and Molecular Bioscience from Newcastle University, and a PhD in Evolutionary Biology from Newcastle University. Currently, Jonathan is an assistant professor of biology at Sattler College in Boston, Massachusetts. Jonathan has been interviewed on podcasts and radio shows including "Unbelievable?" on Premier Christian Radio, and many others. Jonathan has spoken internationally in Europe, North America, South Africa and Asia promoting the evidence of design in nature.