Homology: A Problem, not a Proof, for Evolution

By Jon A. Covey, B.A., MT(ASCP)
Edited by Anita K. Millen, MD, MPH, MA

In the article on vestigial organs I didn't mention that embryologists have thoroughly discredited the idea that embryos trace their evolutionary ancestry during their growth phases. The idea of embryonic recapitulation was popularized by the catchy slogan: ontogeny recapitulates phylogeny. This phrase is still found in high school and college textbooks, which are very slow to change. Ernst Haeckel's drawings of embryos were fraudulent, but they served as the basis for the mistaken idea that ontogeny recapitulates phylogeny. An excellent study by Michael Richardson contains revealing photographs of embryos in the tailbud stage from many species, shows that Haeckel's work and the idea that ontogeny recapitulates phylogeny is remarkably poor science. (Richardson, 1997) The photographs are so telling, that biologists who, perhaps secretly, cling to the belief that ontogeny recapitulates phylogeny, will be forced to abandon that belief.

Sir Gavin de Beer, former Professor of Embryology at the University of London and Director of the British Museum, wrote many books on biology, embryology, and evolution, including Introduction to Experimental Embryology (1926), Development of the Vertebrate Skull (1937), Embryos and Ancestors (1962), Charles Darwin (1963), and Atlas of Evolution (1964). In 1971, he wrote Homology, An Unsolved Problem.

What is homology? de Beer's definition states that it is the study of corresponding organs and structures of plants or of animals. For example, the leaf of an oak tree corresponds to the leaf of an ash tree, and the right forelimb of a dog corresponds with the right forelimb of a horse. [de Beer, p. 3. See the drawings.]

He then said that Darwin's bombshell of evolution, which burst in 1859, had a profound effect on the concept of homology without touching the criteria by which it is established. He says that homology between organs was based on their correspondence with a common ancestor. "What can be more curious," asked Darwin, "than that the hand of a man, formed for grasping, that of a mole for digging, the leg of the horse, the paddle of the porpoise, and the wing of the bat, should be all constructed on the same pattern, and should include similar bones, in the same relative positions?" [de Beer, p. 4] Why should this be curious? It is obvious that God designed the best structure for the function intended. Darwin's ignorance of genetics allowed him to draw many such incorrect conclusions which sold evolution.

de Beer explains that homologous organs provide the evidence of affinity between organisms that have descended with modification from a common ancestor, which is the standard phrase used to define evolution. Furthermore, he says that since evolution is the explanation of the agreement between homologous organs, we can study homology in fossils as well. Perhaps with tongue-in-cheek he says:

"So, provided with a cast-iron explanation in terms of affinity, of inheritance in evolution from a common ancestor, it looked as if the concept of homology was at last soundly based and presented no more problems of principle; however, as will be seen below, it unfortunately does." [de Beer, pp. 4-5]

Clearly, Sir Gavin de Beer did not write this short book to extol the virtues of homology and its support of evolution. He has discovered problems with homology as evidence for evolution. In view of this, it is strange that Dr. Michael Shimmer, Dr. Larry Abele, and other evolutionists who have debated Dr. Duane Gish continue to use the argument of homology to support the theory of evolution, thinking that it is simultaneously evidence against creation.

First, because of the great subjectivity in the eye of the beholder, homology could never be used against creation. An evolutionist looks at homology and can only see descent from a common ancestor with modification. A creationist looks at the same material and sees clear cut evidence for intelligent design. People who use homology to argue against creation do not understand creation. Second, as Sir Gavin says, it is a problem for the theory of evolution rather than a testimony for it. Homology bears the strong signature of an intelligent designer. It is creation from a common design that has produced homologous structures. Similar engineering problems might be solved by using similar designs. As Dr. Gary Parker said, a Ford and a Chevrolet have more in common than a Ford and a sailboat. They share more design features. [Parker, p. 54] Parker also pointed out that when similar organs are found in greatly different creatures such as wings in birds and insects, evolutionists do not suggest that they are related by common descent. Instead, they propose that these are examples of convergent evolution, because these organs are converging into similarity. So-called convergence, a term inspired by evolutionary presupposition, is clear evidence for common design. God created similar structures designed to meet similar needs in widely divergent organisms. The human eye and the eyes of squids and octopuses are similar, but no evolutionist has ever been able to find or even imagine a common ancestor with traits that would explain these similarities.

The Apostle Paul understood that the Creator left His indelible mark on creation and summed up the situation in this way:

"For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who suppress the truth in unrighteousness, because that which is known about God is evident within them; for God made it evident to them. For since the creation of the world His invisible attributes, His eternal power and divine nature, have been clearly seen, being understood through what has been made, so that they are without excuse. For even though they knew God, they did not honor Him as God, or give thanks; but they became futile in their speculations, and their foolish heart was darkened. Professing to be wise, they became fools, and exchanged the glory of the incorruptible God for an image in the form of corruptible man and of birds and four-footed animals and crawling creatures. Therefore God gave them over in the lusts of their hearts to impurity, that their bodies might be dishonored among them." Romans 1:18-24 (NASB)

Theistic evolutionists, those who believe that God somehow directed the course of evolution, have much difficulty in bringing forth the evidence for God's invisible attributes, eternal power, and divine nature from creation because they have no easy way of distinguishing their brand of evolution from atheistic evolution. When some of them see the problems inherent in the purely naturalistic explanation for the origin of the universe and life, it is to those problems they apply the Divine fingerprint. God becomes some kind of god of the gaps or insurmountable problems. In contrast, Paul says the evidence of God is clearly seen in creation. The evidence is so clear that no one has an excuse for not believing in God. The criteria for how God applies His wrath would have to be different if His evidence were not clearly seen in creation. As much as evolutionists want to deny it, and as much as they have argued against it, the argument from design is very powerful evidence for creation, and homology is actually part of the design argument. Why?

Sir Gavin gives us some historical tidbits on the homological concept. He says that Richard Owen introduced the term into biological language in 1843. Owen, however, owes his way of thinking to Aristotle who may be said to have founded comparative anatomy in his Historia animalium (comparative anatomy is essentially the study of homology) which the Apostle Paul would have had the opportunity to study and probably did, considering his accomplished scholarship under Gameliel and his intense desire to traffic in the marketplace of ideas to win the Greeks to the cross of Christ. His appeal in Athens in the midst of the Areopagus is an example of this:

"Men of Athens, I observe that you are very religious in all respects. For while I was passing through and examining the objects of your worship, I also found an altar with this inscription, 'TO AN UNKNOWN GOD.' What therefore you worship in ignorance, this I proclaim to you. The God who made the world and all things in it..." Acts 17:22-24

Paul identified the Athenians' UNKNOWN GOD as the God who created all life and the universe. Aristotle's reference to homology was evidence of design to Paul.

de Beer Identifies Some Problems

Sir Gavin says that there is no doubt whatever that the forelimb in the newt and the lizard and the arm of man are strictly homologous, inherited with modification from the pectoral fin of fishes 500 million years ago. The elbow and wrist joints are identical, and their hands end in five fingers. The bones and muscles also correspond. The shock comes when a careful study of their comparative anatomy reveals that they do not occupy the same positions in the body. "The limbs of vertebrates are always formed from material that is contributed from several adjacent segments of the trunk. In the newt, the forelimb is formed from trunk segments 2, 3, 4, and 5; in the lizard from 6, 7, 8, and 9; in man from trunk segments 13 to 18 inclusive." He explains how this is determined embryologically and anatomically.

Embryology was de Beer's basis for questioning the validity of homology as evidence for evolution. He said that progress in early embryology made such strides there are two levels on which the relations of homology and embryology can be studied:

1. Level one–the correspondence of places of origin of homologous structures in the fertilized egg or embryo of related species
2. Level two–the induction of tissues to undergo differentiation

At level one, de Beer says that the prospective fates of embryonic structures are well known, and they can be traced back to their place on the egg or young embryo of related species. [de Beer, p. 13] They can be observed and proved by experiment. In other words, the wrongful application of homology by evolutionists has been debunked by the scientific method.

Sir Gavin gives us some examples of this logical approach: use of the scientific method to evaluate evolutionary claims. The alimentary canal in vertebrates can form from:

1. the roof of the embryonic gut cavity (sharks)
2. the floor (lampreys, newts)
3. roof and floor (frogs)
4. the lower layer of the embryonic disc, the blastoderm, that floats on the top of heavily yolked eggs (reptiles, birds)

It is evident that homologous structures are known to develop from varying locations in the egg or embryo, depending on the species. Therefore, says de Beer, if the origin of the homologous structures is not from the same part of the egg or position of the cells in the embryo, then they are not genetically related because they are not under the control of homologous genes. If they are not genetically related, they are not the result of descent with modification from a common ancestor.

He draws the same conclusion from a different set of observations. In one species of Polygordius, a primitive worm (primitive is subjective), the trunk of the future worm develops inside the body of the larva, while in another species, the trunk develops outside the larva as a worm-like extension. The adults of both species are virtually indistinguishable. Similar differences are seen in the development of certain mollusks, although the adults are nearly identical.

At level two de Beer studied homologous relations by inducing embryonic tissues to differentiate by diffusing substances from a master structure called an organizer. One study showed that the dorsal lip of a newt embryo can be grafted anywhere into the body of another embryo and will induce the surrounding tissues to differentiate into all the structures characteristic of a vertebrate embryo. If these tissues had been left undisturbed, they would have differentiated into entirely different structures (notochord, segmental muscle plates, kidney tubules spinal cord, brain with eyes, etc.), proving that the nature of a structure does not depend on the place of origin. This should be very disturbing to those who wish to apply homology to the battery of evidences for evolution. Homologous structures should originate at the same places in all descendants of a common ancestor, otherwise the homology has nothing to do with descent.

In another example, de Beer says that if the optic cup is removed in one species of frog the eye lens will not develop, while in another closely related species the lens does develop. He says it cannot be doubted that the lenses of these two species are homologous, yet they differ completely in their mechanism of determination and differentiation. The genes involved are not homologous.

In summary, he says:

"It is now clear that the pride with which it was assumed that the inheritance of homologous structures from a common ancestor explained homology was misplaced; for such inheritance cannot be ascribed to identity of genes. The attempt to find 'homologous' genes, except in closely related species, has been given up as hopeless."

He understands the logical absurdities, quoting S.C. Harland who said that the genes coding for the homologous structures must have become wholly altered during the evolutionary process! This should alarm geneticists, computer scientists, and linguists. It simply doesn't make sense, and de Beer says so:

"But if it is true that through the genetic code, genes code for enzymes that synthesize proteins which are responsible (in a manner still unknown in embryology) for the differentiation of the various parts of their normal manner, what mechanism can it be that results in the production of homologous organs, the same 'patterns' in spite of their not being controlled by the same genes? I asked this question in 1938, and it has not been answered."

Bibliography

de Beer, Sir Gavin, Homology, An Unsolved Problem, Oxford University Press, (1971).

Parker, Gary, Henry M. Morris, What is Creation Science? Master Books, El Cajon, (1982). Call 800-999-3777 to order.

Richardson, M.K., Hanken, J., Gooneratne, M.L., Pieau, C., Raynaud, A., Selwood, L., Wright, G.M., "There is no highly conserved embryonic stage in the vertebrates: implications for current theories of evolution and development," Anat Embryol 196:91-106, (1997).