It can be stated that self-awareness is indicative of an individualized and evolved form of consciousness found in human beings and not manifested to the same extent in animals. A cat or a dog, or any other domestic animal is aware of itself in a relationship to a human being or to others of its kind, but it is not aware of itself as a cat or a dog or other animal. Neither are these creatures aware of themselves as living entities, nor do they have any realisation of the limitations of their own life span. They may have certain instinctive apprehensions, as for instance when sheep or cattle are going to the abattoirs, but the reaction is fear, not understanding. The quality of self-awareness, exclusive to humankind, like the qualities mentioned before cannot have developed as the result of the physical evolutionary struggle. No scientifically understandable mutation of genes could lead to intellectual and personality individualization. The stimulus must have been external. Self-awareness is the recognition of individuality, of uniqueness, but it is also the recognition of human mortality. Therefore did it not go hand in hand with other knowledge humans would be the most miserable of creatures, conscious of their helplessness and the futility of life. How the human consciousness became individualized and the mechanisms of self-awareness are a comprehensive subject beyond the scope of this question and answer procedure. Let us just say that self-awareness in people is something which has been added to humanity from a source outside the material evolutionary stream. It is another distinguishing feature of humankind. It results, in effect, from an individualized expression of consciousness.