To most people, pain is usually nothing more than an annoyance–a twinge of back pain or a prickle of pain from a hangnail. For those who suffer from a chronic pain condition, however, it’s much more than an annoyance. When traditional treatment methods have failed and the pain persists, it might beg the question: why do we feel pain?

Pain is an extremely important genetic adaptation.

At its core, pain is a survival mechanism. It’s the body’s way of forcing an immediate response to prevent further injury. For example, if a person sets his or her hand on a hot stove, nerves will transmit a pain response and trigger the person to pull the hand away, almost before he or she has realized that it hurts. By pulling the hand away so quickly, further damage to deeper tissue is prevented.

In addition to preventing severe injuries, pain can help with the healing process by acting as a reminder. George Dvorsky at io9 explains:

“Given that a traumatic event (like stubbing your toe) set the injury response into action, the pain receptors will continue to sense that an injury has occurred and that you need to be reminded about it until it heals. Consequently, the nerve fibres are specialized enough to recognize an ongoing injury that’s in the healing process.”

However, no matter how useful pain is, it’s still unpleasant. To appreciate why pain is important enough that it’s worth the unpleasantness, though, consider those who feel no pain at all.

A rare genetic condition renders some individuals unable to experience physical pain.

A condition, commonly referred to as congenital insensitivity to pain or congenital analgesia, leaves certain individuals unable to feel pain. At 1st this sounds great, but think of tripping over a pet, fracturing a bone, and not knowing that an injury has occurred because there was no pain. Consider a parent attempting to raise a child who cannot experience pain.

2 individuals with this condition recalled the lengths their parents went to in an effort to prevent injuries:

  • Socks over their hands, to prevent finger-chewing or face-scratching
  • Goggles, to protect the eyes from scratches
  • Helmets, to prevent concussions

Despite these safety measures, both still managed to injure themselves regularly. 1 individual recounts his most frequent childhood injuries:

“Jumping down the stairs was the most common injury I had. I would also injure myself by pushing a swingset away from me and having it slam into my face. At the time I enjoyed the reaction I received from others and the time I would spend in the hospital. Touching hot objects was another one of the most frequent injuries I had. I loved to hear the sizzling of my skin. Broken legs were a very common injury for me.”

Strangely enough, this condition is considered a type of peripheral neuropathy, which can also be a cause of chronic pain. This is because congenital insensitivity to pain is a result of malfunctioning peripheral nerves. Chronic pain from peripheral neuropathy occurs when those same nerves are damaged and, instead of going silent, send an overload of pain signals.

Current researchers are delving into the evolutionary properties of pain.

It’s understood that pain is a survival mechanism, but the individual gene receptors that control pain responses are still being studied. For example, a recent study conducted by Shigeru Saito, et. al. isolated a specific gene for pain receptors in chickens, called TRPA1. By examining the receptor’s function with different stimuli, the researchers found that heat stimulated the TRPA1 gene in chickens.

The researchers also found that a chemical bird repellant stimulated the same pain receptor as heat, the TRPA1 gene, but the responses to the same repellant by other vertebrate species were varied. Additionally, researchers were able to identify 3 amino acid residues involved in the activation of TRPA1 by the chemical repellant.

Although this study involved pain receptors in chickens, and a chicken’s TRPA1 is more similar to that of a cold blooded animal than that of a human, this is still a significant step in the study of pain. It has added to scientists’ understanding of the functional, biological evolution of pain receptors, and might help answer the question: why do we feel pain?

Another field of evolutionary study, evolutionary psychology, gives a potential explanation for chronic pain.

Evolutionary psychology suggests that the pressure to survive and reproduce throughout human history has shaped the human mind. This field of study attempts to identify imprinted, evolutionary traits to explain why people do or experience what they do. For example, close relatives like children or spouses are jealously guarded because of an evolutionary urge to reproduce and pass on genes.

A school of thought in evolutionary psychology suggests that humans have learned that pain can sometimes help them obtain attention, emotional rewards, and sometimes even economic rewards from others and this is why we feel pain. For example, if an individual complains of pain, he or she is the recipient of sympathy. This might suggest that chronic pain is an evolutionary adaptation of sorts.

However, this idea fails to explain the people who suffer from chronic pain without complaint. Many of these people never even pursue treatment for their pain. Some of those who study evolutionary psychology suggest that the way people handle pain–whether they complain or not, and whether they pursue treatment or not–is dependent on personality and cultural influences.

Even if pain–perhaps even chronic pain–is an important evolutionary trait, it shouldn’t be ignored.

Most pain is evidence of an injury or condition that needs time to heal, possibly even a physician’s attention. Chronic pain, or pain that lasts for 3 months or more, can sometimes potentially be accompanied by psychiatric conditions like depression or anxiety. Because of these risks, it’s advisable to always pursue treatment for chronic pain.

What do you think: why do we feel pain?

Image by Craig Sunter via Flickr

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