The idea that there's some way of calculating the odds is wrong. There isn't. Really we don't know what the simplest thing needed is, so calculating the odds of randomly assembling amino acids or to randomly put together the atoms of a DNA molecule. Or to manage to assemble the human genome out of randomly assembled nucleotides is both insufficient and compelling.
We don't presently know what step zero is, so we cannot calculate how likely or unlike it may be. But, even if it were extraordinarily unlikely, it would still necessarily be a better answer than miracles or the supernatural. After all, we have found answers to things and some of those answers have been unlikely occurrences, but none of them have ever been supernatural. The answers to any thing we've ever found answers to have been simple naturalistic forces of things we didn't know. So because the right answer has always been naturalism and never supernaturalism, that is certainly going to be the better answer even if it were far fetched.
If you hear a gallop, you should think horse. Because that's what it commonly turns out to be. But, I freely admit that it might be a zebra. But, the only reason you're asking that I concede the long shot possibility of a zebra is because deep down you believe it to be a unicorn, and think that maybe if the typically right answer isn't certainly the right answer then the never right answer might stand a chance; it doesn't.