[jmsgwd]

> it might take only one intelligent life form for the space to (eventually) get filled with it

It wouldn't need to be intelligent to do this; it could be a self-replicating machine with no intelligence at all - which is orders of magnitude simpler and therefore more likely.

Chaotic initial state -> self-replicating machine -> intelligence is much more likely than chaotic initial state -> intelligence.

(See my other reply to the GP comment about The Recursive Universe, where all this is discussed.)