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In Biology as in Technology, Similarities Do Not Prove the Absence of Intelligent Design


Editor's note: The following is excerpted from the new expanded edition of Granville Sewell's book In the Beginning: And Other Essays on Intelligent Design (Discovery Institute Press). References for cited works are given in this book. ENV contributor Dr. Sewell is Professor of Mathematics at the University of Texas El Paso. He has written three books on numerical analysis, and is the author of a widely used finite element computer program.

In the Beginning Sewell.jpegA November 2004 National Geographic article proclaims that the evidence is "overwhelming" that Darwin was right about evolution. Since there is no proof that natural selection has ever done anything more spectacular than cause bacteria to develop drug-resistant strains, where is the overwhelming evidence that justifies assigning to it an ability we do not attribute to any other natural force in the universe: the ability to create order out of disorder?

As always, the main evidence offered is the "evolutionary tree" of similarities connecting all species, fossil and living. These similarities were of course noticed long before Darwin (many animals have four legs, one head, two eyes, and a tail!); all modern science has done is to show that the similarities go much deeper than those noticed by ancient man.

To our modern minds, these similarities may suggest natural causes: the argument is basically, "This doesn't look like the way God would have created things," an argument used frequently by Darwin in Origin of Species. But if the history of life does not give the appearance of creation by magic wand, it does look very much like the way we humans create things, through testing and improvements.

In fact, the fossil record does not even support the idea that new organs and new systems of organs arose gradually: new orders, classes and phyla consistently appear suddenly. For example, Harvard paleontologist George Gaylord Simpson writes:

It is a feature of the known fossil record that most taxa appear abruptly.... This phenomenon becomes more universal and more intense as the hierarchy of categories is ascended. Gaps among known species are sporadic and often small. Gaps among known orders, classes and phyla are systematic and almost always large.

We see this same pattern, of large gaps where major new features appear, in the history of human technology. For example, if some future paleontologist were to unearth two species of Volkswagens, he might find it plausible that one evolved gradually from the other. He might find the lack of gradual transitions between automobile families more problematic, for example, in the transition from mechanical to hydraulic brake systems, or from manual to automatic transmissions, or from steam engines to internal combustion engines; though if he thought about what gradual transitions would look like, he would understand why they didn't exist.

He would be even more puzzled by the huge differences between the bicycle and motor vehicle phyla, or between the boat and airplane phyla. But heaven help us if he uncovers motorcycles and hovercraft, the discovery of these "missing links" would be hailed in all our newspapers as final proof that all forms of transportation arose gradually from a common ancestor, without design.

The similarities between the history of life and the history of technology go even deeper. Although the similarities between species in the same branch of the evolutionary "tree" may suggest common descent, similarities (even genetic similarities) also frequently arise independently in distant branches, where they cannot be explained by common descent. For example, in a 2004 Nature Encyclopedia of Life Sciences article on carnivorous plants, Wolf-Ekkehard Loennig and Heinz-Albert Becker note that

carnivory in plants must have arisen several times independently of each other... the pitchers might have arisen seven times separately, adhesive traps at least four times, snap traps two times and suction traps possibly also two times.... The independent origin of complex synorganized structures, which are often anatomically and physiologically very similar to each other, appears to be intrinsically unlikely to many authors so that they have tried to avoid the hypothesis of convergence as far as possible.

"Convergence" suggests common design rather than common descent: the probability of similar designs arising independently through random processes is very small, but a designer could, of course, take a good design and apply it several times in different places, to unrelated species. Convergence is a phenomenon often seen in the development of human technology, for example, Ford automobiles and Boeing jets may simultaneously evolve similar new GPS systems.

So if the history of life looks like the way humans, the only other known intelligent beings in the universe, design things -- through careful planning, testing and improvements -- why is that an argument against design?

Image: Military hovercraft, U.S. Navy, via Wikipedia.