Chapter 1

Comparative Similarities: Homology

by Dr. Gary Parker on January 1, 1994

Why should a person’s arm have the same kind of bone pattern as the leg of a dog and the wing of a bat? There are two basic ideas, descent from a common ancestor or creation according to a common plan

Look at your arm for a moment and try to picture the bones inside. There’s one bone attached to the body, two bones in the forearm, a little group of wrist bones, and bones that radiate out into the fingers. As it turns out, there are many other living things that have forelimbs with a similar pattern: the foreleg of a horse or dog, the wing of a bat, and the flipper of a penguin, for example, as shown in Fig. 6. Biologists use the term “homology” for such similarities in basic structure.

Figure 6

Figure 6. Bones in the human arm, the forelimbs of horses and dogs, a bat’s wing, and a penguin’s flipper all share a similarity in basic structural pattern called homology. What does this similarity (homology) mean: descent from a common ancestor (evolution), or creation according to a common plan (creation)?

Why should there be that kind of similarity? Why should a person’s arm have the same kind of bone pattern as the leg of a dog and the wing of a bat? There are two basic ideas. One of these is the evolutionary idea of descent from a common ancestor. That idea seems to make sense, since that’s the way we explain such similarities as brothers and sisters looking more alike than cousins do. They have parents closer in common.

Using descent from a common ancestor to explain similarities is probably the most logical and appealing idea that evolutionists have. Isaac Asimov, well-known science fiction writer, was so pleased with the idea that he said our ability to classify plants and animals on a groups-within-groups hierarchical basis virtually forces scientists to treat evolution as a “fact.” In his enthusiasm, Asimov apparently forgot that we can classify kitchen utensils on a groups-within-groups basis, but that hardly forces anyone to believe that knives evolved into spoons, spoons into forks, or saucers into cups and plates.

After all, there’s another reason in our common experience why things look alike. It’s creation according to a common plan. That’s why Fords and Chevrolets have more in common than Fords and sailboats. They share more design features in common.

What’s the more logical inference from our observation of bone patterns and other examples of homology: descent from a common ancestor, or creation according to a common plan? In many cases, either explanation will work, and we can’t really tell which is more reasonable. But there seem to be times when the only thing that works is creation according to a common design.

I get support for my claim again from Denton,16 in his chapter titled “The Failure of Homology.” Dr. Denton is not only a research scientist with a Ph.D. in molecular biology, but also an M.D. with an intimate knowledge of comparative anatomy and embryology. He admits his desire to find naturalistic explanations for patterns of similarity among organisms (homology), but he also admits the failure of evolutionary explanations.

Like every other scientist, Denton recognizes the striking similarity in bone pattern evident in a comparison of vertebrate fore- and hind limbs. Yet no evolutionist, he says, claims that the hind limb evolved from the forelimb, or that hind limbs and forelimbs evolved from a common source. I was once taught to refer to corresponding parts of the male and female reproductive systems as “sexual homology.” But homology, in that case, could not possibly be explained by descent from a common ancestor; we can’t even imagine that males evolved from females, or vice versa, or that human beings evolved from some animal that had only one sex.

Worse yet for evolution, structures that appear homologous often develop under the control of genes that are not homologous. In such cases, the thesis that similar structures developed from genes modified during evolutionary descent is precisely falsified. Our observation of similarity or homology is real enough, but that’s true, Denton points out, “whether the causal mechanism was Darwinian, Lamarckian, vitalistic or even creationist.’” (Emphasis added.) Although the evidence is not as spectacular and compelling as the biomolecular data, I would say the weight of our present knowledge of homology favors Denton’s final alternative: creation according to a common design.

The non-branching nature of trait distribution produces practical problems for the biologist. One of the students I taught, for example, had a passion for lizard ear bones. He came in late in the evening and early in the morning, always dissecting lizard ear bones, sectioning them, and so on. That got him interested in lizards in general. But he noted that in attempts to classify lizards, one person would go by the field characteristics, and come up with one system. Another researcher would go by the bone patterns, and come up with another system. Internal organs suggested a third, and so on. The pattern is not a branching one suggesting evolutionary descent from a common ancestor; rather, it is a mosaic or modular pattern (which I’ll discuss further in the next chapter) suggesting creation.

Perhaps the clearest anatomical evidence of creation is “convergence.” The classic example is the similarity between the eyes of humans and vertebrates and the eyes of squids and octopuses. Evolutionists recognize the similarity between the eyes easily enough, but they’ve never been able to find or even imagine a common ancestor with traits that would explain these similarities. So, instead of calling these eyes homologous organs, they call them examples of “convergent evolution.” That really means that we have another example of similarity in structure that cannot be explained as evolutionary descent from a common ancestor.

“Convergence,” in the sense of similar structures designed to meet similar needs, would be expected, of course, on the basis of creation according to a common design. And as we’ll see later, both the octopus eye and the vertebrate eye are complete, complex, and totally distinct from one another right from their first appearance in the fossil sequence. Biologist Michael Land17 sounds like a creationist when he mentions in passing that the vertebrate eye “shares design features but not evolution” with the eye of the cephalopod mollusks such as the octopus.

The real focus of Land’s article, however, is “divergence,” the occurrence of quite distinct structures in plants and animals that otherwise are supposed to be close evolutionary relatives. Certain shrimp-like animals that live in deep ocean darkness, he says, have compound eyes with lenses all arranged to focus light at a common point (rather than forming multiple images, as most compound eyes do). But, he continues, some members of the group have “lens cylinders” that smoothly bend the incoming light (because of smoothly varied refractive indices), whereas others have square facets with a “mirror system” for focus (utilizing even a double-corner bounce). Ingenious use of physics and geometry should be evidence enough of creation it seems to me—but there’s more.

Comparing the mirrors with the lens cylinder system, Land says: “Both are successful and very sophisticated image-forming devices, but I cannot imagine an intermediate form [or common ancestral type] that would work at all.” The kind of design in these eyes, he says, seems impossible to explain as a result of evolutionary relationship. So Land goes on to suggest that the shrimp-like animals with different systems should not be classified as evolutionary relatives, even though they are otherwise quite similar.

Even more interesting is Land’s statement about how he felt when he was trying to figure out the mirror system. He said he was “trying not to come to the conclusion that these eyes had been put there by God to confuse scientists.” May I suggest instead that these eyes were put there by God to inform scientists. As such cases show, a mind open to examples of created order can hasten and enrich the scientific search for understanding.

Some evolutionists admit they have failed to find good evidence of evolution in comparing large structures, so they are looking instead for homology among molecules. In a foundational book basically describing the three-dimensional structures first known for proteins, Dickerson and Geis18 make the statement: “One fact … has emerged in the last 15 years from the perfection of protein sequence and structure analysis … We can pin down with great precision the relationships between the species and how the proteins evolved.” Then, with every example they give, they proceed to disprove that evolutionary prediction.

Consider hemoglobin, for example, the protein that carries oxygen in red blood cells. Dickerson says that hemoglobins pose “… a puzzling problem. Hemoglobins occur sporadically among the invertebrate phyla [the animals without backbones], in no obvious pattern.” That is, they don’t occur in an evolutionary branching pattern. I would suggest that they do occur in a creationist mosaic or modular pattern, like bits of blue-colored stone in an artist’s mosaic. We find hemoglobin in nearly all vertebrates, but we also find it in some annelids (the earthworm group), some echinoderms (the starfish group), some mollusks (the clam group), some arthropods (the insect group), and even in some bacteria! In all these cases, we find the same kind of molecule—complete and fully functional. As Dickerson observes, “It is hard to see a common line of descent snaking in so unsystematic a way through so many different phyla … .”

If evolution were true, we ought to be able to trace how hemoglobin evolved. But we can’t. Could it be repeated evolution, the spontaneous appearance of hemoglobin in all these different groups independently, asks Dickerson? He answers that repeated evolution seemed plausible only as long as hemoglobin was considered just red stuff that held oxygen. It does not seem possible, he says, that the entire eight-helix folded pattern appeared repeatedly by time and chance. As far as creationists are concerned, hemoglobin occurs, complete and fully functional, wherever it is appropriate in the Creator’s plan, somewhat like a blue-colored tile in an artist’s mosaic.

The same seems to be true for a fascinating protein called lysozyme. Lysozyme is the enzyme in tears that “bites holes” in the cell walls of bacteria so that they explode. (Listen for the “pop” on a quiet evening!) Egg whites are rich in the same enzyme, and that’s what keeps eyes and egg whites from getting easily infected.

By comparing lysozyme and lactalbumin, Dickerson was hoping to “pin down with great precision” where human beings branched off the mammal line. The results are surprising. In this test, it turned out that humans are more closely related to the chicken than to any living mammal tested! Every evolutionist knows that can’t be true, but how can he get around the objective evidence? In his concluding diagram, Dickerson slips in a wiggly line for rapid evolution, and that brings the whole thing back in accord with his evolutionary assumptions. But notice that his protein data, the facts that he observed, did not help him at all with his evolutionary idea.

In fact, when it comes to many of the similarities among molecules, the theory of evolution is not only weak, it has been falsified. That conclusion was expressed by Colin Patterson19 of the British Museum in an address to leading evolutionists which he gave at the American Museum of Natural History.

Patterson first lamented that his topic, creation and evolution, had been forced on him, and then he acknowledged that he had recently been entertaining non-evolutionary or even anti-evolutionary ideas. Why? Because, he said, after twenty years of research in evolution, he asked himself to name just one thing about evolution he knew for sure—and he couldn’t come up with anything! When he asked other leading evolutionists, the only thing anyone could come up with was that “convergence is everywhere.” (Remember convergence—similarity without common ancestry—discussed earlier?) Finally, Patterson said with dismay, he was forced to conclude that evolution is an “anti-theory” that generates “anti-knowledge”—a concept full of explanatory vocabulary that actually explains nothing and that even generates a false impression of what the facts are.

Patterson said that he finally awoke, after having been duped into taking evolutionism as revealed truth all his life, to find that evolutionary theory makes bad systematics (the science of classification). He then proceeded to examine the molecular data as a creationist would, in simple recognition that creationists produce testable hypotheses, and that now he can understand and explain what inferences creationists would draw from the data, without either agreeing or disagreeing with them. What a superb example of healthy scientific skepticism! Patterson is able to see the data regarding homology in their wholeness, and experience the unbridled freedom to wonder not only how but whether evolution occurred!

Michael Denton20 independently reached the same kind of conclusion regarding homology and the so-called “molecular clock.” After documenting the misfit of molecular data with both of two competing evolutionary views, he writes this summary (p. 306):

The difficulties associated with attempting to explain how a family of homologous proteins could have evolved at constant rates has created chaos in evolutionary thought. The evolutionary community has divided into two camps—those still adhering to the selectionist position, and those rejecting it in favor of the neutralist. The devastating aspect of this controversy is that neither side can adequately account for the constancy of the rate of molecular evolution; yet each side fatally weakens the other. The selectionists wound the neutralists’ position by pointing to the disparity in the rates of mutation per unit time, while the neutralists destroy the selectionists’ position by showing how ludicrous it is to believe that selection would have caused equal rates of divergence in “junk” proteins or along phylogenetic lines so dissimilar as those of man and carp. Both sides win valid points, but in the process the credibility of the molecular clock hypothesis is severely strained and with it the whole paradigm of evolution itself is endangered. (Emphasis added.)

But Denton doesn’t stop with these devastating anti-evolutionary comments (and a comparison of belief in molecular clocks with belief in medieval astrology!). He also describes data from molecular homology as a “biochemical echo of typology,” where typology is the pre-evolutionary view of classification developed by scientists on the basis of creationist thinking.

References and notes

  1. Denton, Michael, Evolution: A Theory in Crisis, Burnett Books, London, Chapter 7, 1985. Return to text.
  2. Land, Michael, Nature as an Optical Engineer, New Scientist, October 4, 1979. Return to text.
  3. Dickerson, Richard E., and Irving Geis, The Structure and Action of Proteins, Harper and Row, New York, 1969. Return to text.
  4. Patterson, Colin, Address at American Museum of Natural History, New York, November 5, 1981. (Summarized by Gary Parker and Luther Sunderland in Acts and Facts, Impact No. 108, Institute for Creation Research, El Cajon, CA, December 1982.) Return to text.
  5. Denton, Michael, Evolution: A Theory in Crisis, Burnett Books, London, page 306, 1985. Return to text.

Creation: Facts of Life

Dr. Parker, a leading creation scientist and former AiG speaker, presents the classic arguments for evolution used in public schools, universities, and the media, and refutes them in an entertaining and easy-to-read style. A must for students and teachers alike! This is a great book to give to a non-Christian as a witnessing tool.

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