When ever evolutionary biologists find a similar looking gene, chromosome, or body part in creatures they have assumed are related, they use such “homologies” as proof of that assumption. Unknown to most people, however, similarly designed chromosomes or bones are often found in animals that are not believed in any way to be related. Animals such as the now extinct marsupial Tasmanian Wolf, for example, appeared in many ways identical to wolves found in the rest of the world, yet was not believed to be ancestral or related. The eye of the octopus is probably more similar to the human eye than any other, yet cannot be traced by evolution to the human eye. The concentration of red blood cells in man is far more similar to that of frogs or fish than to many mammals.
Such common features in unrelated animals are said to have evolved convergently, by accident or due to similar environments. If these similarities were to be found in the expected Darwinian order, they would be listed as “further proof” of the Darwinian creation story. But like most similarities that don’t fit the evolutionary theory, they are not commented on in typical high school textbooks. However, they do demand the question; if homologous or similar structures can exist in totally unrelated animals, how can such similarities then be used as proof of common ancestry in others?
On page 141 in the biology textbook called “Life Science”, drawings of the structures of the batwing, the dolphin flipper, and the human arm are shown as visual support for common ancestry. While the similarity is obvious, and the drawings make good use of the power of suggestion, the idea that these structures could exist in totally unrelated animals is not brought to bear on the argument.
Why not? Shouldn’t a good science text book bring out both the strengths and weaknesses of a given argument? Nor is the possibility of these similarities being the result of “convergence” the only pertinent information being left out of the textbook discussion here. It has been well-known for decades that the wing and arm structures in the various animals are not controlled by the same genes, and therefore cannot be the result of inheritance through common ancestry.
As Gavin De Beer, former director of the British Museum of Nat’l History noted as far back as 1938 and in his 1971 monograph, Homology: An Unsolved Problem ;
“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?”
In fact, the existence of homology in nature, when all its aspects are brought into the picture, seems to give far better support for the idea of common design and Designer than the standard Darwinian story being trotted out in the textbook.