Anxiety and evolution: fight or flight
What is anxiety?
If you’ve detected the theories of Charles Darwin in the account of emotion we’ve just given, you are right. Indeed, emotions are the subject of a fascinating study by Darwin, The Expression of the Emotions in Man and Animals. Published in 1872, this book has long been overshadowed by Darwin’s revolutionary On the Origins of Species (1859). But after decades of neglect, The Expression of Emotions has come to exert a powerful influence on scientific thinking.
Darwin sees emotions as primarily expressive behaviours: automatic, unconscious, and largely innate (rather than learned) physiological changes, facial expressions, and behaviours. What interests Darwin in particular is the range of actions and visible bodily changes that characterize each emotion. These actions and expressions both help the person experiencing the emotion and send signals to those around him or her. In the case of fear, Darwin notes:
the eyes and mouth are widely opened, and the eyebrows raised. The frightened man at first stands like a statue motionless and breathless, or crouches down as if instinctively to escape observation. The heart beats quickly and violently … The skin instantly becomes pale … [and cold] perspiration exudes from it … The hairs on the skin stand erect … the mouth becomes dry …
As the title of Darwin’s book makes clear, he doesn’t regard emotions as a distinctly human attribute. Indeed, Darwin devotes considerable effort to highlighting the continuities (as well as differences) between the animal and human experience and expression of emotion. For example, he writes:
1. An illustration of ’terror’ from Charles Darwin’s The Expression of the Emotions in Man and Animals
With all or almost all animals, even with birds, terror causes the body to tremble…. With respect to the involuntary bristling of the hair [typically caused by fear], we have good reason to believe that in the case of animals, this action … serves, together with certain voluntary movements, to make them appear terrible to their enemies; and as the same involuntary and voluntary actions are performed by animals nearly related to man, we are led to believe that man has retained through inheritance a relic system, now become useless.
Equally controversially for the time, Darwin insisted that the way in which human beings expressed emotions was almost always the same, regardless of ethnicity.
So much for the expression of fear. What about anxiety’s adaptive function? How exactly does it help us? The classic account was formulated in 1915 by a professor of physiology at Harvard, Walter Cannon (1871—1945). He coined the phrase ’fight or flight’ to describe an animal’s typical reaction to danger. Anxiety’s purpose is to alert us to potential threat and to prepare us to react appropriately. And to send a signal to others that they should be on guard.