Some interesting takes on the idea of consciousness that I've read or thought about myself--all are things humans do that other animals do not:
1. The ability to "think about thought". This leads into the ability to think in the hypothetical. We are the only species that can make decisions based on what could happen, as opposed to just what is happening. Perhaps more tragically we are the only ones who can be afraid of things that might happen to us.
2. This requires a different kind of headspace--thinking in hypotheticals--and I think it is also closely tied into language. Consciousness seems to be in many ways a semiotic system. We can attach symbols (or words, or any given image or concept) to a web of other things. Have you ever tried to go about life without "talking to yourself" in your head? It is basically impossible. We need language to process thought on the level of consciousness. (The Bicameral Mind theory mentioned in 'Westworld', though not entirely taken seriously, has a fascinating take on this wherein ancient man supposedly literally did not understand that the voice in their head was their own--the running verbal thought processes were taken to be "commands" from an outside entity...i.e. "gods". Again, it's not a very accepted theory but it shows the extent to which internal monologue is key to the idea of consciousness).
3. From this we branch out into the idea of "meaning". That anything can "mean" something else. I read somewhere that "man is doomed to context". Context is also a key aspect of consciousness. Nothing we do or experience is isolated--it is all inescapably tied into the semiotic web of "meaning" that we internalize over our lives. Further, the contextual nature of our awareness grounds us as no other animal in a place and time. We are the only ones who know that there was a world before us, and that there will be a world after us. We are the only ones who know that we will die. I believe that even an animal that is running for its life from a predator does not "know" why it's doing so, or is aware that it is about to die or what that means. It is a base fear response.
Animals, and very small children, live in a context-free existence. Children eventually grow out of it. Incidentally, if you read the book of Genesis as a metaphorical treatment of this process, it is incredibly fascinating. I.e. when God says "eat not of that tree (of knowledge) for in that day you shall surely die"...it is not that they literally die, it is that they become aware that they will die, thus understanding as no other animal does that their experience is not the totality of reality.
Incidentally, it's also telling that God's first task for Adam was to name all of the animals--in other words, to begin to create that sign system I referred to before.
Just some things I have thought about on the subject...consciousness perhaps can never be fully understood but I like to get these blurry glimpses at it.
As for evolution--I think it's pretty undeniable.
Edit--just a quick note on Koko the gorilla. Her accomplishments have been mostly accepted to have been "embellished" at the very least. In any case, I do not believe for a second that she could understand who or what Robin Williams was, or that he had died, or what that would mean/