[csense]

The question is rather like asking, “If many Americans and Australians are descended from Europeans, why are there still Europeans around?”

Are you suggesting that the differences between nationalities is analogous to the difference between species? If so, then I'd say you have a very odd understanding of logic. Creationists themselves recognize the invalidity of this claim

[csense]

Strike that last sentence:

Creationists themselves recognize the invalidity of this claim