The Genetic and Embryological Impasse of Homology
The discovery which really overthrew homology is that organs accepted as "homologous" are almost all controlled by very different genetic codes. As we know, the theory of evolution proposes that living things developed through small, chance changes in their genes, in other words, mutations. For this reason, the genetic structures of living things which are seen as close evolutionary relatives should resemble each other. And, in particular, similar organs should be controlled by similar genetic structures. However, in point of fact, genetic researchers have made discoveries which conflict totally with this evolutionary thesis.
Similar organs are usually governed by very different genetic (DNA) codes. Furthermore, similar genetic codes in the DNA of different creatures are often associated with completely different organs. The chapter titled "The Failure of Homology" in Michael Denton's book, Evolution: A Theory in Crisis, gives several examples of this, and sums the subject up in this way:
This genetic question has also been raised by the well-known evolutionary biologist Gavin de Beer. In his book Homology: An Unsolved Problem, published in 1971, de Beer put forward a very wide-ranging analysis of this subject. He sums up why homology is a problem for the theory of evolution as follows:
Although some 30 years have passed since de Beer wrote those words, they have still received no answer.
A third proof which undermines the homology claim is the question of embryological development, which we mentioned at the start. In order for the evolutionary thesis regarding homology to be taken seriously, the periods of similar structures' embryological development-in other words, the stages of development in the egg or the mother's womb-would need to be parallel, whereas, in reality, these embryological periods for similar structures are quite different from each other in every living creature. Pere Alberch, an eminent developmental biologist, noted, it is "the rule rather than the exception" that "homologous structures form from distinctly dissimilar initial states."287
The emergence of similar structures as the result of totally dissimilar processes is frequently seen in the latter stages of the development phase. As we know, many species of animal go through a stage known as "indirect development" (in other words the larva stage), on their way to adulthood. For instance, most frogs begin life as swimming tadpoles and turn into four-legged animals at the last stage of metamorphosis. But alongside this there are several species of frog which skip the larva stage and develop directly. But the adults of most of these species that develop directly are practically indistinguishable from those species which pass through the tadpole stage. The same phenomenon is to be seen in water chestnuts and some other similar species.288
To conclude, we can say that genetic and embryological research has proven that the concept of homology defined by Darwin as "evidence of the evolution of living things from a common ancestor" can by no means be regarded as any evidence at all. The inconsistency of homology, which looks quite convincing on the surface, is clearly revealed when examined more closely.
285 Michael Denton, Evolution: A Theory in Crisis, Burnett Books, London, 1985, p. 145.