Sleepy,
Then do you have another theory that doesn't presuppose a creator? You most assuredly did pressupose a creator with the alternate theory you proposed. I'm not saying that you believe or disbelieve in a creator, I'm just saying that the argument that you put forward presupposed a creator, and we both know that there is no evidence for a creator. At least not yet.
You could have said that Ivisible Pink Unicorns could have built life in a way which left the DNA the way it was. In that case you would be presupposing an Invisible Pink Unicorn for your argument. There is no evidence for an Invisible Pink Unicorn, just as there is no evidence for a creator god.
I'm sorry if I came accross the wrong way. I'm not trying to say that you are putting forward the god theory as the best theory, I'm just saying that there is a flaw in that particualr theory you brought up (a creator is necessary for it to work). Because of that flaw, I see no reason to believe it as a possibility.
rem
"We all do no end of feeling, and we mistake it for thinking." - Mark Twain