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.
We are intelligent because we have opposable thumbs and can use tools, which evolved our brains. This is an old one - maybe as old as Darwin's time. I think its mostly ignored now because so many animals - including pandas and other non primates have opposable thumbs or use tools or both. (monkeys and chimps use tools, and recently crows have also been observed to use tools.)
brain size. We do have a large brain to body size ratio. There are other animals with similar ratios and they don't have internets.
We are 'self-aware'. That is to say we recognize ourselves as an individual. It was proven that other primates can recognize themselves in mirrors (putting a red dot on their forehead. when they see their reflection, they touch their own forehead). So that's not exclusive either. its not a bad idea, but so far it doesn't seem to make the
'We ate something' I once read a discussion of how humans might have ingested psychotropic plants or fungi. As you can see, this was 2010. Its not the worst idea, but its hard to prove. Lots of experiments on cats since the '60s have not produced cat's who care to tell us if they are intelligent. Maybe they are just too smart in the first place.
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.
This is really a philosophy question because for now, we have no clue how consciousness works. But other answers have correctly noted that we know it's closely related to our ability to learn, reason and remember.
There are some attempts to explain it though - you could now the famous TED talk about the illusion of consciousness by the philosopher Daniel Dennet. By evolutionary means, we can mainly study the concept of self.
One of the simple philosophies trying to explain consciousness is panpsychism. Panpsychism is virtually a part of hinduism and buddhism and says that everything has some degree of consciousness and our mind is one of the emergences of unity of many little conscious things.
Why did humans/animals evolve to become self-aware of their own thoughts.
Answer is pretty simple. Most mammals are self aware... it is just a matter of degree. It is a lot more advance in humans, but it is there in animals. like pride of Lioness hunting... setting up an ambush together... which means a lion can predict what zebra will do in a situation. And what other lioness will do.
And why have it? The answer is simple... being aware of you own thought, is basically being able to prediction the thoughts of others. And this is pretty useful.
We have the example of lioness pride ambush hunting. It requires a degree of self awareness in order to communicate and in heat of the chase predict what the other members of your pride will do and what will the prey animal will do.
Being alpha (wolf, lion, chimp, elephant, hyena, meerkats) is great. There are many biological benefit (first to eat, drink and have babies). However for a there to be an alpha, there must first be a group to be alpha over. And when there is a group, there is a beta, and while beta might not be able to beat you individually, beta might team up with delta..to remove you.
So as you can see, living in groups quickly leads to complications. And if you can understand others, you can use others to benefit yourself. Much selection pressure there for to evolve consciousness.
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.
Probably density of cortical columns. I tested this on a mouse recently, it was aware I was trying to help it and actually walked calmly into the jar. Released it but did wonder if it will make an appearance again one day.
Perhaps in this case, neural nets are not complicated enough unless the connectivity threshold is in a critical range. This is apparently why we are one of only three intelligent species on this planet, sharing this with dolphins and African Grey parrots. Four if you count octopi.
I speculated a while back based on my knowledge that connectivity modulators like psilocin, xenon and other compounds could be used to trace the actual neural connections responsible. This has been linked to Orch-OR and other QC like phenomena, also allowing for strong AI to be developed by synchronizing classical processors with a quantum link using entangled photons.
Natural selection doesn't select for the type of consciousness. It selects for brains that work for its purposes. The brain I think is like a Conway's game of life. It theoretically can pull off all kinds of tasks, and that can be explained just by the laws of physics acting on the brain.
The question of how the brain creates consciousness is an entirely different question maybe a philosophical one. I have aspergers. I sometimes do some abstract thinking. I sometimes sort of feeling like I'm conceiving of an object with properties that most intuitive theories prove cannot exist. They would say it's just my brain inventing the sentence "This object has those properties" and they're probably right. However, I sometimes actually have a small bit of feel for thinking in one and would feel like I'm conceiving of a real object which is distinct from its formalization which people would see if they looked at an image of my brain. I think we then decide to define consciousness according to the way the brain is in that kind of way.
Animals are not self aware, sentience is the quality of placing yourself in time and space, and the capability of introspection. We humans know we exist, we know we live in a universe, we ponder what's the meaning of life, where we came from and how we came to exist, where we go after we die, animals don't, they act by instinct and have different levels of intelligence, their behavior is written in their DNA code, but they aren't self-aware, this is the basic trait that separates us from animals.
Concerning how we became self-aware, that will depend on your beliefs (another trait of our advanced intelligence), but those who believe in evolution pretty much agree that we developed sentience because our brains developed much further than that of any other species, our advanced cortex and cognitive system gave us this ability. Different religions also have different accounts to our origin and history, in the proto-Indo-European cosmology for example, we are descendant of aliens, called pleiadians or nordic aliens, they came to earth through a portal in the sun, and brought their seed to our planet and gave origin to us, all our knowledge and manifestation of our humanity, like science, art... come from them.