How does this change the FORMULA I'm talking about? It doesn't matter what the specific mechanisms are, you still have to NOT have whatever "expression of the Bmp4 gene" would bring about the wrong kind of beak for the particular variety under discussion.Faith writes:This isn't the way it works. For Darwin's 15 different tanager species there were not 15 different alleles for the shape of beaks, one for each species. Bird beaks are controlled by the expression of the Bmp4 gene. All the different beak shapes are the result of different timing and spatial controls on the expression of the Bmp4 gene. Expression of the Bmp4 gene is under the control of regulator genes with names like Shh and Fgf8.
This is what must have happened with each of the finch types. A beak type got selected for its usefulness with a particular kind of function, and that got passed on and came to characterize a whole population because the alleles for the other beak types were eliminated from the reproductive pool. The same thing happened with other beak types as each found its peculiar adaptation and became isolated from the other types.
In other words, beak shape is under the control of more than one gene and more than one type of gene, and bird gene pools of any species possess a great deal of variation. This is why beak expression is so plastic under the influence of changing environmental pressures.
And I'm aware that some traits are controlled by more than one gene, in fact it has occurred to me that the original "super Genome" that is a necessary assumption of Creationism may have been characterized by more genes per trait among other differences from today's genome, on the idea that junk DNA is genes that were once alive but died down the centuries, probably most of them all at once in the Flood.
But the same principle I'm talking about has to apply no matter how many genes are involved. You still have to SUPPRESS the expression of whatever the underlying genetic formula is for any traits that would compete with the selected trait of the population under discussion. This is a reduction in genetic diversity, and it is NECESSARY in order to get a particular phenotype, and it has to STAY suppressed, OR be eliminated altogether, if that trait is to be preserved.