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Good Grief. No, Airplanes Don't "Evolve" by Natural Law.

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In an article entitled "Survival of the Flight Test: Airplanes Evolve, Too," Live Science reporter Tanya Lewis offers the startling claim that airplanes evolve the same way living organisms do. Come again? That's right, but she's just echoing a paper, "The Evolution of Airplanes," published in the Journal of Applied Physics by mechanical engineers led by Adrian Bejan of Duke University. Their abstract sounds like a throwback to 19th-century orthogenesis:

The prevailing view is that we cannot witness biological evolution because it occurred on a time scale immensely greater than our lifetime. Here, we show that we can witness evolution in our lifetime by watching the evolution of the flying human-and-machine species: the airplane. We document this evolution, and we also predict it based on a physics principle: the constructal law.* We show that the airplanes must obey theoretical allometric rules that unite them with the birds and other animals. For example, the larger airplanes are faster, more efficient as vehicles, and have greater range. The engine mass is proportional to the body size: this scaling is analogous to animal design, where the mass of the motive organs (muscle, heart, lung) is proportional to the body size. Large or small, airplanes exhibit a proportionality between wing span and fuselage length, and between fuel load and body size. The animal-design counterparts of these features are evident. The view that emerges is that the evolution phenomenon is broader than biological evolution. The evolution of technology, river basins, and animal design is one phenomenon, and it belongs in physics. (Emphasis added.)

First of all, what's the constructal law? Lewis writes, "In 1996, Bejan developed a rule, known as the constructal law, which states that 'for any finite flow system to persist, that is, be alive, it must evolve in such a way that it provides easier and easier access to its currents.'" This is absurd; many things persist but are not alive -- for example, ocean currents or tides. And in Darwinian theory, nothing "must evolve" by any rule or law: many organisms simply go extinct or never change (e.g., living fossils). The requirements of powered flight are incapable, in themselves, of forcing mindless laws to conjure up a wing or avian lung. The "constructal law" is, therefore, nothing more than a mental imposition on nature that allows Bejan to salvage mindless Darwinism by making it appear law-driven.

In any event, talk about reductionism! Now, they have made technology, river basins and animal body plans all subsets of evolution, and evolution, they say, belongs in the physics department. Did it never occur to these three engineers (including one from Boeing) that airplanes are intelligently designed?

They seem delighted to offer (finally!) an example of evolution that can be observed within a human lifetime. To equate this with biological evolution, they need to redefine evolution as design (they even call it "design evolution"), and conceive of the human-airplane combination as a species. Note carefully the word "imagination" in this excerpt:


Looking at Fig. 1 [a chart of airplane "evolution" over the years] satisfies precisely this need. The species to watch is the human-and-machine species. New airplane models do not happen by themselves. They are extensions, enclosures of the humans who come together to ride on them. Airplanes are flying buildings. Every model is a new human-and-machine design for moving our bodies, groups, and belongings over the entire globe. This design is changing, and what evolves with it is the movement of humans on the globe. This spreading flow gets better, faster, more efficient, and farther reaching, in accord with the constructal law.

It is hard to be charitable to such logic. You might as well say that teenagers and their smartphones constitute an evolving unit, the teenager-and-smartphone species. Granted, phones sometimes seem like extensions of teen ears. Maybe we should call them Homo smartphonenesis, v. applei and v. androidei. The authors might imagine this "species" evolving according to some kind of natural law toward better, faster, more efficient teen-phone units. The smartphones would then become "extensions ... of the humans who come together" to communicate on them.

Where in this picture do the minds at Apple, HTC, or Samsung come into play? You might think a Boeing engineer would know better than to insult his peers by insinuating that their work is not mindful. But if the "design" that produces "human-and-machine" units is a natural law (and therefore, mindless), why wouldn't that same natural law produce "human-and-scientific-paper" units? It would force us to conclude, not in an insulting way, but as a logical deduction, that their paper is mindless.

Human designs do change over time, but only with mindful intent. Intelligently guided change is not evolution in any coherent Darwinian sense. Intelligent-design champion Phillip Johnson's most effective critique of Darwinism began with his focus on its essential nature: that it is unguided, purposeless, aimless, and mindless. This is true of both mutation and natural selection. The human mind doesn't work like Darwinism. Aircraft designers use their minds! They may improve their designs over time, but they always have goals: they know what they want, and apply thought, intention, and determination to reach those goals.

Minds make matter do things it would not naturally do, like making tons of metal fly into the air. The authors' analogy is backward. We don't infer from birds that airplanes evolve; we infer from airplanes that birds were designed! In Flight: The Genius of Birds, Ann Gauger explains why a bird could never emerge by a materialistic process such as natural selection:

Here's the problem: natural selection is blind and unguided; it has no sense of direction ... it doesn't know where it's going. The lack of foresight is the major problem. We know that if you throw all the parts for a 747 into the middle of a room and turn on a fan and blow everything around, you're not going to end up with a 747. We know it doesn't work that way, intuitively -- even when you've got all the parts! Organisms are much more complicated than a 747: much more complicated, and they're integrated wholes; they're not the sum of their parts.

See here for our repeated refutations of Tim Berra's fallacious notion that cars evolve in a Darwinian fashion. The emergence of this "Evolution of Airplanes" paper, and Live Science's cheerful coverage of it, show that Berra's Blunder has not yet succumbed to our critique.

The end of the paper, by the way, acknowledges, "Professor A. Bejan's research was supported by the National Science Foundation." So if you're a U.S. taxpayer, you helped pay for this. Just thought you'd like to know.

Photo credit: Michael B./Flickr.