>We all began as single cells (zygotes) and somewhere along the way we suddenly became conscious, whereas a moment before, we were not conscious.
You may not have realized it, but many would debate the assumptions in that sentence. ^_^
Sidestepping a decent into the definition of 'conscious' itself for now, one could propose that consciousness is an inherent nature of matter itself, and it just emerges further/grows in complexity as the zygote develops.
A more justified explanation would be that consciousness is the capacity to learn and adapt to the environment, so we don't have to say 'it just emerges'. It's there, even at cell level, but it's not inherent in matter, that makes no sense. It's probably inherent in self replicators that live in a competitive environment, but not just any matter. Rocks don't learn and adapt and have no reason to do so.
Since "conscious" is an aggressively undefined term, you can say anything about it that feels good. I say "aggressively" because any attempt at a precise operational definition brings random testy objections out of the woodwork, typically invoking varying degrees of woo.
Ultimately, nobody has determined a practical need for a definition, or really for the word, outside of discussion of people in comas, so reasonable people let it go.
You may not have realized it, but many would debate the assumptions in that sentence. ^_^
Sidestepping a decent into the definition of 'conscious' itself for now, one could propose that consciousness is an inherent nature of matter itself, and it just emerges further/grows in complexity as the zygote develops.