I don’t know how you calculate those odds but it is also possible that consciousness doesn’t require any physical “container” to exist. Perhaps it just takes advantage of them as you already suggested.
One current view is that "we exist" because our universe is built/designed/screwed around with such that "we can exist".
If so, the odds are 100% certain that consciousness probably starts at the point where the little teeny tiny computer gizmos in/on Dna TURN ON.
Or at least at the moment nothing else is on the horizon.
Once you get consciousnes down at the DNA level all the supposition about evolution becomes so much dross and drek.