Changing ONE WORD (of consequence) in your post, and it's in the realm of the Creationist pre-supposition.
Dan's right that we admit to having pre-suppositions, but you are blind to yours.
Different conclusions based on the same observations are due to differing assumptions. You just won't admit your assumptions.
Except that we have observed genetic variation arise from a population derived from a single organism. It is hardly an assumption. It is an observation.