Evolution succeeds where "Intelligent Design" fails in describing the natural world.

Bruce and Frances Martin

Intelligent Design is a well-worn concept in theological argument. Since ancient times, the harmony and complexity of natural organs and systems have served as "proof" for the existence of God. In modern times before Darwin (1859), William Paley (1802) was the most famous proponent of this idea. Remember the watch found on the heath? Paley supposed that, just as the discovery of such an intricate mechanical setting would be proof of a human designer, so the intricate mechanisms of the natural world, such as the human eye, prove the existence of a benevolent, divine designer. Today design has new currency in the latest anti-evolution thrust. Pennock gives a list of its academic sponsors (Pennock 1999, 29) and cites Philip Johnson as "the most influential new creationist and unofficial general" of the Intelligent Design school. Johnson is a retired professor of law at the University of California at Berkeley and author of Darwin on Trial (1991) and Defeating Darwinism (1997). Since the word design itself implies plan or purpose, it appears redundant to say "intelligent design" unless one means to imply intelligence of the highest order or divine intelligence. Despite its abstract aura, the origin of the term is undeniably religious.

By their own definition, creationists believe that the world in general, and mankind in particular, are designed and exist for a divinely ordained purpose (Pennock 2001). Therefore, creationists reject the possibility that new species appear through evolution by common descent, which proceeds without a preordained purpose. They offer as the alternative Intelligent Design: the purposeful fashioning of each species by an intelligent designer-by implication God. Like its forerunner, creation science, this movement presumes that by undermining Darwinism they ensure Intelligent Design reigns as the sole available alternative, ignoring numerous other creation myths. A full defense of evolution is available elsewhere; our purpose in this short article is to cite some cases incompatible with Intelligent Design.

Does the real world show evidence of wise, omniscient design? To be plausible, an argument must take all the facts into account. The scientific study of biology shows us that existing species have serious flaws, belying claims of a beneficent creator. Intelligent design spokesmen ignore vestigial organs, anatomical inefficiency, destructive mutation, the sheer wastefulness of natural processes, and the findings of molecular genetics. The constant interplay of random mutations honed by selection pressures during evolution produces many instances of poor design. What follows are a few of the less technical of the hundreds of examples of flaws noted by paleontologists and other students of evolutionary processes.

Vestigial Features

Darwin was not only convinced by the success of evolution in explaining numerous instances of common descent, but also by its ability to account for vestigial organs, "parts in this strange condition, bearing the stamp of inutility." These organs are of little or no current use to an organism but are probable remnants of an earlier form from which the organism evolved. Intelligent Design has no explanation for these organs. As Stephen Jay Gould has put it, "Odd arrangements and funny solutions are the proof of evolution-paths that a sensible God would never tread but that a natural process, constrained by history follows perforce" (Gould 1980; Gould in Pennock 2001, 670). Let's look at some examples.

Cockroaches and other insects may grow an extra set of wings, as did their fossilized ancestors. Unlike most other snakes, boa constrictors possess small vestigial hind legs. Crabs possess small useless tails under their broad, flat bodies, remnants of some ancestral form. Flounders lie flat on the sea floor and in the adult both eyes are on the same side of the head, but when young the eyes are on opposite sides of the head and one moves to the other side! The earlier stage is a clue to an evolutionary path. The result is a wrenched and distorted skull.

The frigate, a non-aquatic bird, does not benefit from the webbing on its feet. In flightless birds the number of usable limbs is reduced from four to two with the presence of two non-functional limbs. Penguins possess hollow bones although they do not have the same need for minimal body weight as flying birds. Otherwise fully aquatic animals such as sea snakes, dolphins, and whales must rise to the surface to breathe air. Modern whales exhibit several non-functional vestigial traits. Fetuses of baleen whales bear teeth that are absorbed as the fetus matures; adult baleen whales do not have teeth.

Paleontologists proposed that whales had evolved from land mammals with legs, and therefore, in an example of its predictive power, the theory of evolution forecast that legs would be found on fossilized whales. In recent years the evolution of whales from now extinct land mammals has become well documented through newly found fossils from the Eocene epoch, about 50 million years ago (Wong 2002). The fossilized whales contain well-defined feet and legs. In modern adult whales, the front legs have evolved into flippers and the rear legs have shrunk so that no visible appendages appear. Hindlimbs still appear in the fetuses of some modern whales but disappear by adulthood. Externally invisible, vestigial diminished pelvic bones occur in modern adult whales. Evolution accounts for these useless vestigial elements as leftovers in the development of whales from land mammals, but they remain unaccounted for by Intelligent Design.

Anatomical Inefficiency

Some anatomical features that may be useful to a creature do not show efficient design one could term intelligent. They testify instead to the process of natural selection. Tails have a widely varied role in mammal bodies. They appear essential for monkeys, but the small, wispy tail in a large elephant seems useless. Tails are absent in adult apes and humans, except they appear in early embryos and are residual in the coccyx at the end of the vertebra. In some human babies a residual tail is clipped at birth.

Why should moles, bats, whales, dogs, and humans among others possess forelimbs based on the same bones that have been adapted in each case unless inherited from a common ancestor? Starting from scratch, an engineer could do a better job in each case. In pandas a normally small bone in the wrist has undergone significant enlargement and elongation so it is opposable as a thumb to the other five fingers, enabling them to strip leaves from a bamboo stalk (Gould 1980; Gould in Pennock 2001, 669). To achieve this feat, the thumb muscles normally assigned to other functions have been rerouted. It is difficult to see how this anatomical architect would receive another commission.

The early embryos of most animals with backbones have eyes on the sides of the head. In those such as humans that develop binocular vision, during development the eyes must move forward. Sometimes this forward movement is incomplete and a baby is born with the eyes too far apart.

In mammals the recurrent laryngeal nerve does not extend directly from brain to larynx, but upon reaching the neck bypasses the larynx and drops into the chest where it loops around a lung ligament and only then retraces up to the larynx in the neck. While a one-foot length of nerve would be required for the direct route from brain to larynx in giraffes, the actual length of the doubled-back nerve from the chest of giraffes may reach twenty feet (K.C. Smith in Pennock 2001, 724-725).

There are many features of human anatomy we might wish were better designed. Our jaws are a little small to accept wisdom teeth that are often impacted and may need pulling. The openings of our tubes for breathing and swallowing are so close that we often choke. In humans the appendix serves no apparent purpose, but it is infection-prone, leading to inflammation and potentially fatal appendicitis. In men the testes form inside the abdomen and then drop through the abdominal wall into the scrotum, leaving two weak areas that often herniate, requiring surgery to relieve pain. Also in men the collapsible urethra passes though the prostate gland that enlarges in later life and impedes urine flow. Anatomists cite many more examples of such inefficient or useless structures, such as nipples in male primates.

Creationists often cite the human eye as a model of perfection for which Darwinism cannot account, claiming that such a complex organ could not be created by natural selection. But throughout the animal kingdom eyes have evolved many times, presumably beginning with plentiful photosensitive material followed by a stepwise incremental buildup over generations to the current organs. And the human eye is far from a model of perfection. In all vertebrate eyes the "wire" from each of three million light-sensitive retinal cells passes in front of the retina, and the collection is bundled into the optic nerve, creating a blind spot. This set-up is just the reverse of what any designer would construct: wires leading away from the backside, not light side, of the light-sensitive cells (Dawkins 1987). On the other hand, the wires do lead from the backside of the separately evolved eyes of the squid, octopus, and other cephalopods. Why does the designer favor squid over humans?

Instead of the efficiency and elegance one expects from Intelligent Design, we see numerous vestigial characteristics and instances of poor design. Such anomalies are both expected and accommodated by evolution. Only evolution offers a self-contained explanation of why more than 99 percent of the species that have lived on Earth are extinct. What sport does a benevolent, omniscient, and omnipotent deity receive from visiting on humans and other mammals all sorts of afflictions including parasitic bacteria, viral diseases, cancer, and genetic diseases?

These and many other examples suggest that any Intelligent Design must have been undertaken by a committee of fractious gods who could not agree. Taken at face value, invocation of Intelligent Design supports an argument for polytheism.

Of course creationists might respond to these and other examples by saying that the ways of God are mysterious and inscrutable, and that we are not wise enough to comment on the means by which he achieves his ends. If anyone offers this argument, what gives him license to propose Intelligent Design as the means by which God achieves his ends? Such a personal view is patently religious, and does not belong in any science classroom.

Destructive Mutations

The study of molecular evolution strongly reinforces and extends the classic whole animal conclusions for evolution, while appearing whimsical at best for an intelligent designer. Modern evolutionary theory regards genetic mutation in the DNA of a species as the source of favorable variations that nature selects for their value in aiding the survival of an individual. But mutation occurs randomly, and in most cases the variation is harmful and results in miscarriage, deformity, or early death. Such mutations are passed from one generation to the next, sometimes lurking in recessive genes until they meet a recessive partner. One example is cystic fibrosis, which causes mucus buildup in lungs, liver, and pancreas. Sickle cell anemia results in poor blood circulation, general weakness, and when inherited from both parents, painful crises owing to sickling and clumping of the red cells. Phenylketonuria prevents infant brain development. Muscular dystrophy wastes muscles and often leaves the victim helpless. In other cases such mutations are dominant. Huntington's Disease causes gradual deterioration of brain tissue in middle age. Hypercholesterolemia causes heart disease due to cholesterol build-up. Neither intelligence nor design seems at work in producing such cruel mutations, though modern evolutionary theory fully accounts for nature's fickleness.

Discoveries of Molecular Genetics

In the genetic material, DNA, the sequence of four nucleic bases furnishes three-letter code words for the sequence of twenty amino acids that occur in proteins. Owing to similarities among the properties of some of the twenty amino acids, substitutions may occur without consequence for proper protein folding and function. For many animals it has proved possible to follow the sequences of both nucleic bases in DNA and amino acids in proteins to spot the changes that have occurred over time. One example is the blood protein hemoglobin, which is a tetramer composed of two alpha and two beta chains working in concert to bind four oxygen molecules. For the beta chain of hemoglobin, the number of amino acid differences compared to that in normal adult humans of 146 amino acids appears in parentheses after the listed animal: gorilla (1), gibbon (2), rhesus monkey (8), dog (15), horse and cow (25), mouse (27), chicken (45), frog (67), and lamprey (125) (Campbell 1987). Clearly, species more closely related to man have fewer differences from humans in their hemoglobin. Since each amino acid substitution requires millions of years to occur, a time scale for branching descent from a common organism according with evolutionary theory is more probable than creation by an intelligent designer.

The known library of DNA and protein sequences is now so huge that numerous comparisons between organisms are possible. If evolution had not already been elaborated by Darwin, we would be led to it by the more recent results of substitutions in molecular sequences. Many amino acid substitutions result in inactive mutant proteins that are not further elaborated by the organism, if it survives the mutation. On the other hand, many substitutions do not impair function and result in amino acid sequence variation of a functional protein, as in the example of the beta chain of hemoglobin above. Furthermore, in humans there are more than 100 amino acid substitutions in the 146-amino-acid beta chain of normal adult human hemoglobin that still yield a functional protein, and most carriers are unaware that they bear a hemoglobin variant. On the other hand, the substitution of only the third amino acid in the beta chain of human hemoglobin gives rise to an aberrant hemoglobin that aggregates within and produces sickling of the red cell with consequent reduced oxygen-carrying capability. This kind of trial-and-error probing involving numerous inter- and intra-species amino acid substitutions has evolution written all over it; it is very difficult to ascribe any design or anything intelligent to this process.

Human Nature

Is it any more than an overweening human ego that proposes intelligent design for such a poorly designed creature? In this egoism, creationists confirm in a perverse way that they have great difficulty rising above their animal origins. It is by reducing influence of ego that the nobler aspects of human nature emerge in humanistic values, values which have been appropriated by some religions.

Of course, evolutionary history fails to induce the warm and fuzzy feeling inspired by Intelligent Design. People would rather believe in a benevolent creator who cares for them. Evolution offers no mercy for the individual or species that lack the traits enabling them to compete in the struggle for food or adapt to changing environments. Fossil evidence shows the number of species that have failed these trials. An Intelligent Designer would create only successful species, but evolutionary theory can account for the many unsuccessful ones. If Intelligent Design fails so badly to account for the real world, aside from the emotional appeal of a wise providence, is there any justification for its continued promotion?

Addendum: The Law of Evolution

We end with a comment on the status of evolution-as fact, "just a theory," or something in between. In the physical sciences there are many observations or facts that have given rise to generalizations: two of these are the law of conservation of matter and the law of definite proportions (which states that when two or more elements combine to form a compound they do so in definite proportions by weight). The statements of facts and their convenient generalization to laws are expressed in terms of macroscopically observable and weighable quantities. The overarching explanation for these laws is achieved in atomic theory, which is expressed in terms of invisible atoms and molecules. No one thinks that atomic theory is "just a theory," for it possesses extraordinary explanatory power and provides the context in which many of the conveniences of our civilization depend. Thus we proceed from many observations or facts to their generalization in terms of laws, both levels macroscopic, to a theory expressed in terms of invisible entities.

If we now apply this scheme to biology, we see that the concept of evolution is at the law level, as it summarizes the results of a large number of observations or facts about organisms. The analogous theory is natural selection or other means by which evolution is achieved. Unknown nearly 150 years ago to Darwin, explanations of macroscopic evolution in terms of microscopic genes and molecular sequences of nucleic bases in DNA are known to us. Placing the concept of evolution at the law level clarifies its status; it is not a theory.

In contrast, the premise of Intelligent Design fails to meet even the most fundamental elements of rational inquiry. By being able to account for everything by divine edict, Intelligent Design explains nothing.