The Fall of the Homology in Tetrapod Limbs
We have already examined homology's morphological claim-in other words the invalidity of the evolutionist claim based on similarities of form in living things-but it will be useful to examine one well-known example of this subject a little more closely. This is the "fore- and hindlimbs of quadrupeds," presented as a clear proof of homology in almost all books on evolution.
Quadrupeds, i.e., land-living vertebrates, have five digits on their fore- and hindlimbs. Although these may not always look like fingers or toes, they are all counted as "pentadactyl" (five-digit) due to their bone structure. The hands and feet of a frog, a lizard, a squirrel, or a monkey all have this same structure. Even the bone structures of birds and bats conform to this basic design.
Evolutionists claim that all living things descended from a common ancestor, and they have long cited pentadactyl limb as evidence of this. But they know that this claim actually possesses no scientific validity.
Even today, evolutionists accept the feature of pentadactylism in living things among which they have been able to establish no evolutionary link. For example, in two separate scientific papers published in 1991 and 1996, evolutionary biologist M. Coates reveals that pentadactylism emerged two separate times, each independently of the other. According to Coates, the pentadactyl structure emerged independently in anthracosaurs and amphibians.289
This discovery is a sign that pentadactylism is no evidence for a "common ancestor."
Another matter which creates difficulties for the evolutionist thesis in this respect is that these creatures have five digits on both their fore- and hindlimbs. It is not proposed in evolutionist literature that fore- and hindlimb descended from a "common limb"; rather, it is assumed that they developed separately. For this reason, it should be expected that the structure of the fore- and hindlimbs should be different, the result of different, chance mutations. Michael Denton has this to say on the subject:
[T]he forelimbs of all terrestrial vertebrates are constructed according to the same pentadactyl design, and this is attributed by evolutionary biologists as showing that all have been derived from a common ancestral source. But the hindlimbs of all vertebrates also conform to the pentadactyl pattern and are strikingly similar to the forelimbs in bone structure and in their detailed embryological development. Yet no evolutionist claims that the hindlimb evolved from the forelimb, or that hindlimbs and forelimbs evolved from a common source… Invariably, as biological knowledge has grown, common genealogy as an explanation for similarity has tended to grow ever more tenuous… Like so much of the other circumstantial "evidence" for evolution, that drawn from homology is not convincing because it entails too many anomalies, too many counter-instances, far too many phenomena which simply do not fit easily into the orthodox picture.290
But the real blow dealt to the evolutionist claim of the homology of pentadactylism came from molecular biology. The assumption of "the homology of pentadactylism," which was long maintained in evolutionist publications, was overturned when it was realized that the limb structures were controlled by totally different genes in different creatures possessing this pentadactyl structure. Evolutionary biologist William Fix describes the collapse of the evolutionist thesis regarding pentadactylism in this way:
The older textbooks on evolution make much of the idea of homology, pointing out the obvious resemblances between the skeletons of the limbs of different animals. Thus the `pentadactyl' [five bone] limb pattern is found in the arm of a man, the wing of a bird, and flipper of a whale, and this is held to indicate their common origin. Now if these various structures were transmitted by the same gene couples, varied from time to time by mutations and acted upon by environmental selection, the theory would make good sense. Unfortunately this is not the case. Homologous organs are now known to be produced by totally different gene complexes in the different species. The concept of homology in terms of similar genes handed on from a common ancestor has broken down.291
On closer examination, William Fix is saying that evolutionist claims regarding "pentadactylism homology" appeared in old textbooks, but that the claim was abandoned after molecular evidence emerged. But, unfortunately, some evolutionist sources still continue to put it forward as major evidence for evolution.
289 Coates M., "New paleontological contributions to limb ontogeny and phylogeny," In: J. R. Hinchcliffe (ed.), Developmental Patterning of the Vertebrate Limb, Plenum Press, New York, 1991, 325-337; Coates M. I., The Devonian tetrapod Acanthostega gunnari Jarvik: postcranial anatomy, basal tetrapod interrelationships and patterns of skeletal evolution, transactions of the Royal Society of Edinburgh, 1996, vol. 87, pp. 363-421.