The only other option seems to be that the first replicator just appeared out of the blue, in one step.
Seeming so, if one doesn't look too close.
Chemical reactions, even of a good quanitity of mid-sized molecules like aminos or nucleics, don't take up a lot of room.
I think about all the little nooks and cranies in every rock across the planet, under the sea, pond, lake, ocean edges and bottoms and I imagine there must be trillions upon trillions of these little test tubes where collisions and reactions are taking place. The timing of these reactions is also quite fast, in relation to waiting for a dental appointment for instance, and I think that over a few million years the probability of some short simple self-replicating chain of molecules natrually coming into being is .. well ... inevitable.
Not really "out of the blue" but close, I suppose.
Darwin takes it from there.