Using these extreme examples of loss of genetic diversity, that normally lead to extinction, does not mean that a precipitous loss of diversity occurs in all speciation events. The millions of SUCCESSFUL species that have existed are evidence that whatever loss of genetic diversity they experienced during divergence from the main population was not enough to cause extinction. These species thrived and added diversity to their genome, presumably through mutation, since there is no evidence for another mechanism. Numerous examples of mutations occurring have been given in this and other threads and no one has successfully shown that this did not lead to increased genetic diversity.
Faith's continuing argument in thread after thread is that (I think I have this right) all ancestral "kinds" had "super genes" that contained all the possible alleles and that these have been continuously reduced with each successive divergence (speciation). As far as I can tell, she is unable to provide a single shred of evidence to support her hypothesis, while many others have posted evidence that comparisons of ancient DNA with modern DNA do not show the existence of these super genes.
The only thing that examples like Cheetahs or dogs shows is that when genetic diversity is reduced within a few generations the result is usually extinction.
In fact, extinction is the usual out come of most speciation events. For example, in entomology we see many satellite populations of insects that adapt to exploit new food sources, habitats, modes of reproduction or development, etc. These populations often do not breed with the main population because of various isolating mechanisms. Most of these "new" species only last a few generations and then become extinct, because some aspect of the environment they adapted to changes and they cannot adapt to this new challenge. The new species that are lucky enough to continue adapting flourish, but most do not and most leave no trace of their existence once they are gone. The reason we know this is happening is the direct observations of scientists studying these organisms.
The creationists argue that macroevolution cannot happen but have not presented a coherent idea to explain all the observations of life's diversity and history that can compete the explanations incorporated in the Theory of Evolution. If they had a better explanation it would already have been accepted and used by scientists to carry out their research and quest to understand nature. The arguments for an imagined barrier to macroevolution have all been based on ad hoc fantasies about the genomes of species past and present that have no supporting evidence.
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