often will whip out some impressive
calculations which purport
to show that it is so extremely improbable
that only a fool
would think it could have happened
However, examination of any of these calculations will show they are invalid, due to various problems and invalid assumptions.
Common problems with calculations include:
They calculate sequential trials, when the primordial chemistry would allow many simultaneous trials, lowering it by orders of magnitude.
They calculate for modern proteins, or in some cases bacteria, simply due to random events. This isn't even the abiogenesis theory.
There is also the very large assumption that life can only exist like it does on Earth. On the same elements, in the same temperature range, with the same atmosphere, with DNA and the same proteins, and the like. There is absolutely no evidence that life can only exist like it does here.
All the flaws with the calculations make them totally useless for any prediction as to how likely it is for life to form on its own. Perhaps it is extremely rare -- or maybe common.