What did it feel like before you were born? The question is oxymoronic. We're not fully unconscious unless we're dead or as good as dead in a coma. Even in deep sleep, the body is sensitive to itself on various levels. Our unconscious side is still conscious, as it were. I wrote an article specifically on this question about the relation between consciousness and death (link below).
Anyway, my point there was just a roundabout way of stating the obvious, which is that what it's like to seem like something is the mark of consciousness, and thus we'd tend to imagine the state of being dead by comparing it to what it's like somehow to be alive, which would miss the point.
Yes, I'm assuming here standard naturalism, which is that consciousness is tied somehow to brains, so anything without any kind of brain attached to sensors isn't conscious.
I suppose there's a natural balance of forces. Just like gravity, entropy isn't all-powerful. Nature is certainly creative as well as destructive, so even if entropy will triumph over everything in the very end, that's a long time away and there's a lot more going on here and now. I'm curious, though, about whether nuclear fusion is as systematic in resisting entropy as the natural selection of organic forms.
Yes, we were conscious as animals or proto-humans for hundreds of thousands of years before we improved our stone tools. But behavioural modernity marked the transition to a fuller, personal, encultured, linguistic, symbol-using consciousness that also saw the explosion of technological ingenuity. I don't think that's accidental. Again, there are degrees of consciousness, and thus degrees of existential enlightenment.
