Children acquire it at about age three. We are the only animals to do so. There are names for it - theory of mind and intentionality - but I'll just call it self-awareness. We are usually unaware of self-awareness until it's implicated in our survival.
Self-awareness is a two-level process. Our close relatives, chimps, make it to the first level. They are aware of their own minds and can recognize themselves in a mirror; a level that infants acquire at two. But chimps never make it to the next level of being aware of other minds. If they did, they would be writing newspaper columns and readers would be imagining the mind of writer. They would even be imagining what fictional characters like Garfield or Kami the Trout might think.
It's not surprising to discover that we are self-aware but Dr. Ajit Varki takes it a step further in his book, Denial: Self-Deception, False Beliefs, and the Origins of the Human Mind.
What is the evolutionary advantage of such a thing? If self-awareness is so great, why haven't other smart animals like crows, dolphins, elephants and apes acquired it?
Well, by itself, there is no evolutionary advantage says Dr. Varki. In fact, it's a real downer.
Self-awareness leads to the grim conclusion that we are doomed. Once I become aware that others exist, I become acutely aware of my own mortality. Though the minds of others, I feel their death as a personal experience. The paralyzing prospect of death leads to depression, hopelessness, and despair. What's the point of going on?
So, there must be some other acquired trait that amends for the bad effects of self-awareness. That quality is denial. Denial of death and risk allows us to blithely go about our daily business without the dark cloud of depression hanging over our heads.
Denial of our mortality allows us to perform deeds both heroic and foolhardy.
Firefighters charge into burning buildings to save people. Leaders take risks and succeed. People build houses on floodplains regardless of the likelihood of flooding. Fools take off from hills in hang gliders with little training (as I did, breaking both arms). Fools and heroes are only determined in retrospect.
Depression is a more realistic view of our lives with self-awareness, says Varki. When the gloss of denial is removed, the pitfalls and existential angst of the human condition become apparent. Denial of risk and death can be seen for what is - a global delusion. But the combination of self-awareness and denial are a powerful duo. Arts and technology flourish. Society benefits through individual risk-taking.
Self-awareness and the ability to imagine what others are thinking encourages the development of complex architectural, military, and technological projects to be undertaken that couldn't be done without massive organization.
Climate-change deniers, however, are in a separate class. Flooded homes and broken bones affect individuals but climate change is global and forever - at least as far as our species is concerned.
On small scale failures, we can learn from our mistakes. The global experiment of climate change can't be re-run. The outcome could be the demise of our species, which, of course, I refuse to believe.