I think you should be proud of yourself… you have provoked @Eddie enough to defend my less-than-perfect descriptions against your virtually senseless criticisms. I am in total awe… (of both you and Eddie, for different reasons).
I will have to admit that my choice of the phrase “genetic molecules” was unwise - - because it allows some readers (aka you, Ben) to think I just mean the raw materials of genes. In fact, I was trying to specify the molecule chains that make up specific genomes. So this convinces me that I should stick to the term “genome”… at least for now.
While all the DNA complexities on earth are fully expressed by a surprisingly small number of amino acids it still seems quite clear to me that the “active genomes which make a mammal a whale” NEVER existed in land mammals before a chain of MUTATIONS created these genomes in whales.
The only way we can conceivably ever think that “whale genomes” are hidden away in a land-based mammalian population is if, millions of years from now (and maybe not even then), a branch of whales somehow returned to the Earth’s continents and re-adapt to living on the land. But it is hard to say how much of the unique whale genomes may get “consumed” in the process.
It makes sense that bird DNA may have a considerable load of Dinosaur genomes buried in their chromosomes… because birds EMERGED out of the dinosaur matrix.
Equally so, it makes very little sense to think that bird DNA is ALSO “pre-loaded” with a hidden set of genomes that would make a kangaroo if only they were switched “ON”… because during the rise of dinosaurs there was NO SUCH THING as a Kangaroo.
To construct the argument so as to enlist a genetic theory of “kangaroo DNA in bird DNA” is to abuse the term genome … and to ignore the common sense meaning of the phrase “kangaroo DNA” to mean “those parts of kangaroo DNA that make a mammal a kangaroo”.