Practically the most frequently encountered traditional argument for evolution is homology of vertebrate limbs. Vertebrates, of course, are animals which are provided with a backbone. In this context, Jonathan Wells, author of the famous book Icons of Evolution (2000. Regnery Publishing Inc.) declared that “In fact, next to the Darwinian tree of life, homology in vertebrate limbs is probably the most common icon of evolution in the textbooks.” [p. 61] And what did Dr. Wells mean by “icons of evolution”? He was referring to popular evidences claimed to support evolution but which nevertheless misrepresent the truth in some fashion. [p. 7]
Apparently British anatomist Sir Richard Owen noticed that bat wings, dog legs, human arms and dolphin flippers (for example) all exhibit similarity in the arrangement of bones. He called these similar structures “homologous” and the phenomenon “homology.” Sir Richard considered that this situation exhibited a common plan for all these features or a blue print in the mind of the creator.
Since Sir Richard’s time in the 1840s however, Darwin published his famous Origin of Species which brought about a shift in scientific opinion. In the 20th century, neo-Darwinists declared that homologous features had come about as the result of “common ancestry.” Common ancestry is the idea that as generations follow their predecessors, evolutionary processes lead to many modified versions of an original basic feature. Thus, as Dr. Wells explains in his chapter on homology “common ancestry is [now] the definition of homology as well as the explanation.” [p. 62] But, says Dr. Wells, “The problem is that now homology cannot be used as evidence for evolution except by reasoning in a circle.” [p. 63] An example of a circular argument is: My cat is black because she is black.
The circular nature of the definition of homology does not stop many biology textbooks from promoting this idea as evidence for evolution, anyway. But there is no foundation or evidential support for the argument. For example, now that we can sequence genomes, we know that seemingly homologous features in various organisms, are not due to similar genes. Why then are they so similar? The mechanism that produces these similar features in different taxonomic groups, then remains unknown. [p. 62] Creatures, for example, which exhibit closely similar homologous features as adults, may develop them through embryonic stages which are entirely different. [p. 71] Furthermore the opposite situation sometimes is true. Similar developmental processes may produce totally different appearing adults. As Dr. Wells summarizes “The lack of correspondence between homology and developmental pathways is true not only in general, but also in the particular case of vertebrate limbs.” [p. 72] Dr. Wells thus argues in summary: “If continuity of information does not come from genes or developmental pathways, how do we know if comes from descent with modification?” [p.77]
The bottom line is that homology is an evolutionary explanation based on no known mechanism, and on a circular argument with no supporting evidence. As a matter of fact, every time biologists use the term convergence to explain why completely different creatures exhibit a similar feature, they have rejected the idea of homology by way of common descent. The widespread modern appeal by scientists to convergence (separate lines of descent), demonstrates why the term homology is so useless.
Sir Richard Owen was right, homologous features instead display a common blueprint and common design from the mind of God. Evolutionists should discard their argument based on homology and rewrite their textbooks!
Is Homology Evidence for Evolution?/ Long Story Short (YouTube, 8 min)