To understand the origins of pain, ask a flatworm

It's always interesting to remember that, scientifically-speaking, we all came from a single celled organism, which eventually evolved into all life as we know it. Along the way, we picked up some interesting characteristics from our different ancestors of life. We got meiosis from eukaryotic organisms, bones from fish, and--per the title of this post--pain detectors from flatworms. Pain, while it isn't most amazing feeling, is very important for survival.

Now, it may not seem particularly vital to know where these biological processes have derived from, but according to biologist Paul Garrity of Brandeis University in Walton, Massachusetts, it’s actually really helpful. Getting a big picture view of how the systems are built gives us a clue on how pain detection might have originated millions of years ago [Sanders].

The study results feature a protein, TRPA1, a pain detector located on the outside of human cells and the cells of many other animal species. It helps many different animal species detect and escape anything that might harm them, including dangerous chemicals, bodily injuries, and harsh temperatures. What’s interesting about TRPA1 is that its triggers vary among different animals. In some animals, the protein is activated by cold, but in others, it’s activated by heat.

The experiment conducted used heat as a trigger for the flatworms. There were two groups, one group with the TRPA1 protein and the other without. The flat worms with the protein avoided the heat, but the ones without the protein didn’t care. The study concluded that TRPA1 is involved in flatworms responses to danger—at least by heat.

Although pain may be unpleasant in the moment, it signals to our bodies that danger is imminent and ultimately protects us from harm. Without pain, we wouldn't know when to stop or when we were pushing our bodies to their limits. For example, if we didn't feel pain, there would be nothing to stop us from sticking our hands in boiling water, damaging our cells and hindering our usage of those nerves and muscles.

While the development of sexual reproduction in eukaryotic cells is just a tad more exciting than the development of pain receptors in flatworms, all of these evolutionary processes make it possible for us to experience the life the way we do today. Without them, we would be nothing more than a single cell.


Reference article:

To understand the origins of pain, ask a flatworm. Laura Sanders. https://www.sciencenews.org/article/understand-origins-pain-ask-flatworm.