>>In summary, from a particular kind of dog, say a chihuahua, we cannot ever
>>get a Saint Bernard. Is that your argument?
>
>Moorad,
>
>I don't think so. I'm not sure that the question of dog breeds contains
>gist of the same argument but I'll comment on it anyway. Not knowing much
>about the history of dog breeds or having any genetic studies indicating
>the amount of genetic variability residing in chihuahuas or Saint Bernards
>I would go out on a limb and say that we could not expect to get a Saint
>Bernard out of a Chihuahua. Remember that both dogs (and other dog breeds
>for that matter) were derived from breeding of wild dogs. Also not all dog
>breed necessarily came from the domestication of just a small number of
>wild dogs from a single population but were likely domesticated from many
>differnt wild dogs from different populations. The net effect of this is
>that there was a large pool of natural variation to draw upon in breeding
>programs. Thus it was not new mutations that are being drawn upon to
>produce new breeds but mixing of a large gene pool.
>This is completely different than taking a single dog breed like a
>Chihuahua and selecting features overtime and ending up with a Saint
>Bernard. The Chihuahua contains only a small subset of the total genetic
>variability in the gene pool of all dogs and so by themselves have
>effectively lost a large number of genes that would be needed to make a
>Saint Bernard. Only by going back to the "stock" could one "recreate" a
>Saint Bernard. I don't know that much about dog genetics so I might be
>wrong. The example I usually use is that of corn varieties. You would be
>hard pressed to make popcorn out of sweet corn because each of the five
>varieties of corn has been so selectively inbred that there is virtually no
>genetic variation and thus very little oportunity for deriving one variety
>from another. Only through hybridization can one reclaim genes that have
>been lost in a particular lineage.
Can these questions be settled at the molecular level? That is, wouldn't the
complete knowledge of the chihuahua genome and that of the Saint Bernard
answer our question?
>One question that comes of this that I have always had for global flood
>advocates that never seems to be addressed specifically is where the
>genetic variation came from that allowed the diversification of animals
>after the flood. In the dog breed example. Two dogs can only contain so
>much genetic diversity and yet we see they being held up as the example of
>microevolution. What the YECs often fail to point out is that dog breeds
>were derived from selection on traits from an already large genetic pool
>(large population of wild dog species/subspecies). Were did that genetic
>pool come from in the first place?? For example focussing on a single gene
>(for this example I don't have specific data) I would expect there may be
>30 or 40 varieties among dog breeds collectively. At best there would only
>have been a couple of varieties of that gene in the two dogs that jumped
>off the ark. One must postulate incredible rates of necleotide
>substitutions in order to accomodate the amount of variation in just
>domestic dog breed not to mention wild dogs and their possible relatives.
>Joel
These are interesting questions which ought to be answerable the day we know
what every species is at the molecular level. I do not claim to know.
Moorad