It's not just that 3 billion years ago it would not have been predicted. It's more the case that it would have been literally beyond all possible imagination ... you could not have even conceived of how an eye (for example) could possibly ever appear and then become vastly more advanced and effective over the passage of time. You would not even have any concept of what sight or vision ever could be.
As far as the Darwin analogy is concerned - he was not around 3 billion years ago to predict evolution. He was only able to finally verify that process because by the 1830's when Darwin was gathering his data, huge strides were already being made across all areas of science, inc. iirc earlier descriptions of something very similar to evolution.
On the issue of why nobody has yet published a complete explanation of exactly how our sensory system along with the brain, produces the effect that we call “consciousness”, I suspect that is because the most advanced and sophisticated areas of science are not concerned with debates about “consciousness” (it's not part of what physicists, chemists, mathematicians, or even most biologists normally concern themselves with). And it's also an area that has got a lot of attention from philosophy and religion where they have been debating it for thousands of years … mostly in the context of claims for it being evidence of a soul and hence evidence for God … and that sort of religious-philosophical debate is not something that many scientists want to waste their time getting drawn into.
But, I have just given you the basic outline of a “theory” for what consciousness actually is and what causes it. And if we look in the research literature for recent papers (the last 30 years, say), I would not be at all surprised to find quite a large number of papers from psychology, medicine, neuroscience and similar fields describing something essentially similar to what I just described … i.e. describing how continuous exchanges of large amounts of information between the sensory system and the brain, are probably responsible for the effect that we call “consciousness”.
Certainly you will find loads of papers describing (for example) how the functioning of the brain is clearly the principal causal component producing what we call “consciousness” (mainly because we know that if areas of the brain are prevented from working, then certain parts of consciousness also stop … and conversely, if certain parts of the brain are deliberately stimulated with drugs or electrical impulses etc., then the patient experiences specific conscious effects and experiences, albeit the “conscious” experiences are being stimulated entirely by that artificial use of drugs and electrical impulses … i.e. the patient reacts as if experiencing real events going on around him/her, but actually it's just an effect caused by the application of electrical signals or certain drugs).