This would suggest that you wouldn't rule out the creation of artificial consciousness by a conscious agent like a human being? The only thing you seem to rule out for sure is the spontaneous emergence of consciousness. So, much like Ranvier's "conservation of of purpose" law, you postulate a kind of "conservation of consciousness" law. I can't really argue against that because it's simply an assertion of something that you believe to be true. The only thing I would point out is that other conservation laws (such as "conservation of energy") are arrived at by Inductive generalization from specific cases. i.e. they stand or fall by our ability to verify or falsify them.I believe it [consciousness] has always existed. The "beginning", if there was one, was when it existed, or at least when it became active. For us, where it "comes from", can be understood by understanding that consciousness can only be acquired as a result of the help and guidance from an already existing consciousness. Consciousness cannot arise in a vacuum. If nothing is conscious, then there is no substrate from which it could arise.
The evidence available so far seems to me to falsify "conservation of consciousness". i.e. the only place in the universe where we know consciousness to exist is the surface of the planet Earth. And we have a lot of evidence that at some point in the past the surface of the Earth did not exist. You've said in the past that life (and therefore consciousness?) could have been carried here on asteroids/meteors/whatever. I've pointed out that those objects also didn't exist at some point in the past.