Researchers Find Evolutionary Purpose behind Pain in Humans


Pain makes people grumpy, irritable, and unpleasant. However,  University of Texas researchers say that experiencing pain helps people from suffering further damage. For example, grabbing a hot cup of coffee causes slight burns to the hand that lasts hours or sometimes days. Researchers say that enduring pain from minor injuries is an evolved survival mechanism that has been shaped by pressures including from predators.

In the study, researchers found that squids that behave extra cautious after experiencing even a minor injury are more likely to live another day.

"Squid perform a stepwise and quite stereotyped sequence of defensive behaviors when they feel threatened, often starting when the predator is still quite distant," first author of the study Robyn Crook said in a press release. "Because we can grade their responses from low to high levels of perceived danger, it gives us a way to measure how injured and normal squid assess danger differently as a predator approaches them and initiates an attack."

For the study, the researchers from the Medical School observed the behavior of squids with minor injuries (one of their tentacles cut off - an injury that does not affect their ability to manoeuvre) in laboratory tanks. Injured squids were more likely to be attacked by predators, black sea bass when compared to their uninjured fellows. When pursued by the bass, these squids gave a tough fight and in fact displayed defensive mechanisms better than their uninjured counterparts.

When the researchers treated the injured squids with an anesthetic that blocked their pain, they failed to show any superior defense mechanisms nor did they responded strongly enough to escape the bass.

The researchers were unable to determine whether the pain experienced by humans after injury is similar to what squids feels after they have been harmed. But researchers said that the sensory activity that triggers enhanced defensive behavior is akin to sensory processes that causes pain after injury in humans.

"If we can understand more about what the natural, 'intended' purpose of nociceptive sensitization is, we might be in a better position to find new ways to treat its pathological expression in humans," Crook said.

The finding is published in the Cell Press journal Current Biology on May 8.

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