Why did humans/animals evolve to become self-aware of their own thoughts. That is, why don't humans act and compute like a machine, or walking zombie. In my mind, such creatures would still be as smart and equally capable of surviving, the only difference being they don't experience the phenomenon of self-awareness. (To understand my question think: unconsciously sleep walking)
There have been many proposals over the years as to why human consciousness has emerged and how, or even what it is.
Most of us will not be surprised to know that there is no consensus about an answer here. Its hard to draw a trend from a single example.
Here is a little survey of the one's I've heard.
These theories, from when I was a student are so discounted now, you can't find too much record of anymore since they were pre-internet and also they seem so unlikely now.
More modern theories have locked onto social configurations of human societies which drive intelligent adaptations. This is stemming from observations that human evolution (the rate at which genetic variants are retained in the gene pool) are accelerating since humans have become social.
These new theories while standing on some amazing evidence are still feeling around in the dark - stuff about how social interactions have created a preference for intelligence-like traits. There is probably something to that - once intelligence gets a toehold it is a clear advantage. But how did it show up only once and why us? I think that's the hard part that science has, for the moment, given a rest.
I don't think you can ever ask or answer for that matter WHY questions in biology. The only answer there is: because it works. Asking why questions implies that there was a reason, and reason cannot exist alone by itself. Reason is held by someone or something. And reason is something that doesn't exist, it is something we created and use for our own purposes and we cannot attribute it to anything else having one. Now, if you asked "how?", that's an answer biology was created for.
There could have been many outcomes to everything in biology but this is the one that appeared and works. This doesn't mean that it is some sort of theoretical or practically optimum, but the law of this universe is survive long enough to improve if needed.
I know that this is an opinion, but it's as close to the answer that you can get. If someone gives an answer to the WHY question, you could never prove it, or you could find evidence for all the possible reasons. And we can't also tap into the reasons of the universe because our intellect and modes of expression are way lower than the universe has.