I'm wondering why you think Old Testament creation oughtn't be reductio'd ad absurdum. The way I see it, it's equally absurdum as that which was reductio'd from it.
Old Testament Creation: A superhuman being, not from Earth, decided one day to create a universe. He kind of just splunked bits and pieces down, one day at a time. Strangely enough, he created electromagnetic radiation before there was anything to radiate it. Weird. And then he went on to create the Earth in a very flat way. It must have rounded out all on its own, because God didn't create it that way. And then, after creating millions of species of insects and fishes and birds and reptiles and worms and bacteria and parasites in just six days, he takes a whole day just to think of a better life form than that. You'd think he'd have figured out that the awesomer life forms were smarter and better at moving around long distances. And then he made dinosaur bones to totally fake us out.
Spaghetti Creation: A superhuman being, not from Earth, decided one day to create a universe. He kind of just splunked bits and pieces down, in no particular order. Strangely enough, he created a beer volcano before creating midgets. Weird. And then he went on to create the Earth, round as it is. I think that bit's more accurate than in the other one.... Anyway, he created a few species of each kind of animal and kind of let them breed and differentiate, in two days, took three days off, and then made some midgets. (Apologies to those of you amongst the forumers that go by midgets, little people, or any number of politically correct names, but FSM-ism makes a lot of jokes about that. I'll try to keep those to a minimum) Then, he spent the rest of the day, since creating midgets was easy, laughing and suchlike at them. Meanly. And he's been messing with the universe with his noodly appendages ever since, in order to fool scientists.
What science tells us: Well, we don't know much for sure, but there sure do seem to be a lot of fossils around that show intermediate forms between common ancestors and current species... let's call this theory evolution, and say that they're all decended from the same ancestor, a really long time ago, seeing as there're tons of evidence for it. Oh, and about that whole start of the universe. We don't know much about that for sure either, but we're pretty sure that there was a lot of pyrotechnics involved. We'll be sure to tell you as soon as we figure something out. But it's going to be less ridiculous than either of those other two theories -- I can tell you that much for sure.