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Homologous structures and genes (Talk.Origins)
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Evolutionist Gavin de Beer (1971) has shown that homologous structures arise from different, non-homologous genes, which means that they cannot be derived from common ancestors. Source: Kofahl, Robert E., 2003. Handy dandy evolution refuter, chpt. 10.
(Talk.Origins quotes in blue)
1. It was 1971 when de Beer made his argument. That was before technology for manipulating DNA made it possible to examine genes directly, so de Beer's conclusions (and those of Hardy 1965, making essentially the same argument) were based on indirect evidence. Since then, many similar genes have been found to participate in the development of homologous structures.
The genes Talk Origins is referring to are called Hox genes. They are genetic switches that turn on and off other genes. While these Hox genes are similar in all animals, the genes they switch on and off to form so-called homologous structures are often different.
These Hox genes are actually a benefit to creation science, because they provide a simple explanation for the large degree of variety within Created kinds.
Granted, some of the examples raised by de Beer have not yet been explained in detail. For example, some organs considered homologous arise from different layers of embryological tissues. But although such cases are not explained, that does not mean they are unexplainable.
The issue here is not that they are not explained—after all, evolutionists are good at inventing just-so stories to explain away any problems—but rather that this is contrary to what is expected from common descent. The simple fact is that this is a failed prediction of common descent, but is expected with created kinds.
We now know that organs can be stimulated to grow in many parts of the body (such as eyes growing on a fly's wings) simply by ensuring that the proper signalling chemicals are present. Thus homologous organs arising from different areas may result simply from mutations in where signalling proteins are expressed.
Interesting idea, but the Hox genes for these so-called homologous organs activate different genes, so it is not a case of a simple mutation.
The difference in finger development between birds and theropod dinosaurs shows an example of how a small difference in development can lead to a nonobvious difference in adult form.
This is irrelevant, since it has nothing to do with either genetic or embryological differences of so-called homologous organs.