The Evolutionary Roots of Anxiety
By Rachel Griep, Biology and Psychology, 2022
Often characterized by rapid breathing and a pounding heart, anxiety is a familiar feeling that everyone has experienced at one point in life or another. Anxiety disorders are currently the most prevalent mental illness in the United States. According to the Anxiety and Depression Association of America, 18.1 percent of the adult population (or approximately 40 million people) suffer from an anxiety disorder each year. Although unpleasant, anxiety is useful and has been shaped over many generations through natural selection. But, anxiety, like all good things, is no longer good in excess and too little anxiety can be just as detrimental. In order to understand and effectively treat anxiety disorders, we must understand the evolutionary roots and benefits of anxiety as well.
Researchers view emotions such as anxiety as physiological and cognitive response patterns that evolve through natural selection to help humans achieve specific goals and avoid threats. Psychologists have long recognized the evolutionary benefits of anxiety: John Bowlby, Mary Ainsworth, and Melanie Klein discussed the benefits of separation anxiety in infants. In his book Fears, Phobias, and Rituals, psychologist Isaac Marks discusses stranger anxiety, which arises in infants around six months of age. Researching other species, specifically primates, has shed light on the evolutionary roots of stranger anxiety, as infanticide is a strong selective force in many animals; evidence shows that human infants are more likely to be abused or killed by strangers than by those who are familiar. Infants who develop stranger anxiety tend to be the ones who survive. Transcultural and universal fears such as separation and stranger anxiety are most likely adaptive. It is important to note that if infanticide were rare, this evolutionary hypothesis would not hold up.
Transcultural and universal fears such as separation and stranger anxiety are most likely adaptive.
Some fear responses are primitive and involuntary, such as a response to a loud sound or crash, whereas other fears develop over time and are learned from example. Infants often first form separation anxiety after experiencing their mother’s absence for the first time. Then with further exploration and a better understanding of death, children develop a fear of heights, monsters, lions, and tigers. Middle childhood is characterized by a fear of injury and accidents, and adolescence is characterized by the development of the more complex fear of social isolation. Children evolved to develop domain specific fears to evolutionarily recurrent danger. In the 2012 Childfund Alliance report “Small Voices, Big Dreams,” child fears from over 5,000 people from 44 countries were recorded. The report found that a majority of children, including children growing up in urban environments, have a fear of “dangerous animals and insects.” Evolutionary fears are not catching up with modern day threats — one is much more likely to die from a car crash now than a poisonous snake bite.
Evolutionary fears are not catching up with modern day threats — one is much more likely to die from a car crash now than a poisonous snake bite.
There is even an evolutionary explanation behind agoraphobia. Agoraphobia is defined as a type of anxiety disorder in which people avoid places or situations that cause them to feel panicked or embarrassed. Mild agoraphobia is comparable to animals in the wild not wanting to leave their home territorial range. Animals that travel beyond their familiar range often experience danger, and increased wariness helps them survive.
People can find joy in anxiety as well. People use fake anxiety-inducing stimulants such as horror movies as entertainment and as a way to train themselves to handle anxiety when it becomes real. Horror movies work because they play to the common fears that reside inside almost every human being, such as environmental stressors, predation, social isolation, contagion, and intraspecific violence. These fears are known as universal triggers. Domain specificity is an evolved sensitivity to these specific dangers. It is the hypersensitivity of domain specificity that leads to category expansion until harmless objects become included in a particular category, ultimately leading to anxiety disorders. For example, someone who has developed a phobia of moths may have experienced the category expansion of predation until it not only included harmful predators such as snakes, and spiders, but also a harmless species such as moths.
Anxiety is a defense shaped through natural selection. As treatment of anxiety disorders by prescription medication becomes more prominent, it is important to understand in which situations anxiety is necessary and to distinguish between which physiological aspects of anxiety reflect abnormalities and which reflect normal operations of the anxiety system. Through understanding the evolutionary roots of anxiety, the most effective treatments to anxiety disorders may be found.
DOI: 10.1016/0162–3095(94)90002–7
DOI: 10.1016/j.cub.2012.11.055
