Historical Overview of Stress
Although the human brain has evolved over hundreds of thousands of years into the complex organ that we now have, like the simplest of animals a part of our brain still is activated by what is interpreted as threats coming from the world in what has been identified as the fight/flight response. The fundamental decision-making process of all animal life forms is to enhance survival chances, which involves an assessment of staying to fight off the threat or of running away from the threat to find safety. In either case, a perceived threat stimulates the body to activate micro- and macro-body responses to enable taking either task by increasing the heart rate, increasing sweating, thickening the blood to increase oxygen supply, sharpening the senses, and focusing attention on the threat or what we now identify as The Fight or Flight Response. Additionally, with regard to one’s own body,
When danger threatens, your adrenal glands release adrenaline [known as epinephrine in the USA], norepinephrine, cortisol and other hormones and chemicals designed to carry out important functions necessary for dealing with the threat. The effect is to make you more alert and to help you to run faster or fight harder. (The 6 Healthy Habits, 2010, para. 1)
As humans evolved both biologically and socially, the brain grew into a more complex organ with the development of many more aptitudes besides survival against life threats by choosing between fight or flight in the untamed wild. In time, threats were less about life and death survival and more about threats regarding finding a safe place within the complex social systems, with many more possible responses besides the fight/flight response. However, the brain experienced fear from life-threat and from intersocial threat as the same and issued the same biological response of fight/flight, no matter the source of that fear.