Are you saying that even if the system was complex, it would have had enough chances to develop that odds are it would have?
IMHO, the issue of propabilities is simply another of the red herrings.
There are two bigg things. First when you start at one limit, as simple as things can get, the only direction that you can go is towards being more complex.
Second, you are dealing with very large numbers. The flask that contained whatever the initial broth was confined in was really, really big, with lots and lots of material.
Third, there is a filter. The things that work are kept, those random changes that don't work get discarded.
Aslan is not a Tame Lion