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Seventeenth-century French philosopher René Descartes conceived of living things as complex machines, a concept now known as the "machine metaphor." In 1998, Bruce Alberts (who was then president of the U.S. National Academy of Sciences) wrote that "the entire cell can be viewed as a factory that contains an elaborate network of interlocking assembly lines, each of which is composed of a set of large protein machines."1
In Salvo 20, Casey Luskin wrote about how such machines pose a problem for unguided evolution and provide evidence for intelligent design (ID).2 Luskin focused on three molecular machines in particular:
1. ATP synthase, which operates like a rotary engine, recharges molecules of adenosine triphosphate (ATP), which in turn provide energy for just about every function in a living cell.
2. Kinesin, which runs along microscopic fibers called microtubules, transports cargoes throughout the cell.
3. The ribosome, which is a combination of proteins and RNAs, translates messenger RNA (which is transcribed from DNA) into proteins.
These are only a few of the many hundreds of molecular machines that have been identified in living cells.
Luskin argued that complex molecular machines, which function only after all of their parts are in place, could not have been produced by unguided evolution but only by a goal-directed intelligence. In other words, molecular machines provide evidence for intelligent design.
Sometimes the Metaphor Backfires
Charles Darwin called his theory of evolution "descent with modification," and he insisted that the process was undirected. Some people have tried to use the machine metaphor to illustrate evolution, but their efforts have backfired. In 1990, biologist Tim Berra published a book titled Evolution and the Myth of Creationism that included photographs of some automobiles. Berra wrote, "if you compare a 1953 and a 1954 Corvette, side by side, then a 1954 and a 1955 model, and so on, the descent with modification is overwhelmingly obvious."3 Since automobiles are engineered, however, the series of Corvettes actually illustrated design rather than undirected evolution. In 1997 Phillip E. Johnson, a critic of Darwinism and advocate of intelligent design, called this "Berra's blunder."4
In 2014, three engineers published an article in the Journal of Applied Physics comparing the evolution of airplanes to the evolution of animals. According to the authors, "Evolution means a flow organization (design) that changes over time," and they argued that animals and "the human-and-machine species" (airplanes) "evolved in the same way."5 But once again, the comparison of machines and living things implied design rather than undirected evolution.
According to pro-evolution philosophers Massimo Pigliucci and Maarten Boudry, the machine metaphor should be abandoned altogether. In 2010 they wrote: "Creationists and their modern heirs of the Intelligent Design movement have been eager to exploit mechanical metaphors for their own purposes." So "if we want to keep Intelligent Design out of the classroom, not only do we have to exclude the 'theory' from the biology curriculum, but we also have to be weary [sic] of using scientific metaphors that bolster design-like misconceptions about living systems." Pigliucci and Boudry concluded that since machine metaphors "have been grist to the mill of ID creationism, fostering design intuitions and other misconceptions about living systems, we think it is time to dispense with them altogether."6
Organized from the Inside Out
But there are better reasons for us to be wary of the machine metaphor than wanting to keep intelligent design out of classroom. Eighteenth-century German philosopher Immanuel Kant pointed out that a machine is organized by an external agent from the outside in, while a living thing organizes itself from the inside out. Kant wrote that a living thing "is then not a mere machine, for that has merely moving power, but it possesses in itself formative power of a self-propagating kind which it communicates to its materials though they have it not of themselves; it organizes them."7
According to philosopher of biology Daniel Nicholson, "despite some interesting similarities, organisms and machines are fundamentally different kinds of systems . . . the former are intrinsically purposive whereas the latter are extrinsically purposive." Thus, the machine metaphor "fails to provide an appropriate theoretical understanding of what living systems are."8
Biologist (and intelligent design advocate) Ann Gauger has written that "the machine metaphor fails," in part, because living organisms are "causally circular beings."9 Not only do new cells require existing cells, but also many biosynthetic pathways require the very molecule that is being synthesized. For example, the biosynthesis of the amino acid cysteine requires an enzyme that contains cysteine.10 Without cysteine, a cell cannot make cysteine. Similarly, ATP synthase consists of more than a half-dozen protein subunits, each of which requires ATP for its biosynthesis.11 In other words, ATP is needed to make the molecular motor that makes ATP.
So the machine metaphor is inadequate as a description of living organisms. Then what about the inference to design from molecular machines? The inference is still justified, because the machine metaphor is appropriate for isolated structures such as ATP synthase, kinesin, and the ribosome. Each of these consists of several parts that are precisely arranged by a cell to utilize energy to perform a specific function (which is how "machine" is usually defined). None of them can perform their functions if parts are missing or arranged incorrectly. They point to intelligent design just as much as machines made by humans.
An organism, however, in contrast to an isolated structure, rearranges its parts over time. An organism imposes organization on the materials it comprises, and its organization changes throughout its life cycle.
To see how remarkable this is, imagine a machine familiar to most of us: a laptop computer. If a laptop computer were a plant or animal, it would start out as a protocomputer consisting of perhaps a few transistors, a little memory with some software, and a battery on a small circuit board. Then it would obtain materials from its surroundings to fabricate other components, and it would make its circuit board larger and more complex. Along the way, it would find ways to recharge its own battery. It would also write more programs. After reaching maturity, the laptop would run its programs by itself—imagine keys on the keyboard going up and down as though pressed by some unseen finger. If components were damaged, the computer could repair or replace them while continuing to operate. Eventually, the computer would fabricate one or more protocomputers, each capable of developing into other laptops just like it.
A lot of design goes into laptop computers. How much more design would have to go into making a laptop computer that could do all the things listed above? No one knows. But such a computer would certainly require more design, not less. And the design would be radically different from human design, because, after the origin of the protocomputer, the design would be intrinsic rather than extrinsic.
So the inference to design from molecular machines is robust, but it's only the beginning. There is design in living things that far transcends the machine metaphor—and it should inspire awe. •
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