Why do we get goosebumps?

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Researchers think they’ve finally unraveled the mystery of getting goosebumps.

It’s a question that has fascinated scientists for centuries. Charles Darwin himself as well as many contemporary scientists have pondered on the issue. Indeed, goosebumps have a clear function for animals with a thick coat of hair, as it protects them from cold. But we humans don’t really seem to benefit from this biological reaction. So… Why do we still get goosebumps?

Our Ancestors

“Goosebumps had a clear function for our ancestors who lived millions of years ago and had more and thicker body hair,” says researcher Ya-Chieh Hsu. “They probably benefited from such a mechanism.” When we get goosebumps, an insulating layer of air can form between the hairs, which makes the body cool down less quickly. So goosebumps actually retain heat and thereby increase the chances of survival. Many animal species can still get goosebumps, although this is reserved for mammals because they have a coat. In other words, goosebumps would be a relic of evolution inherited from our hairy ancestors. The question, however, is why this reaction has not slowly disappeared in humans over time. Is it really just a relic, or could it still have an underlying function?

A long-lasting mystery

The phenomenon goosebumps was for a long time an enigmatic phenomenon. If it is cold, goosebumps as can be read above, has a clear function. Also, upright hairs can make an animal look larger and therefore more dangerous. However, people have far too little hair on their bodies for this latter and terrifying function of goosebumps. There are no stories of lions shivering in front of a person with goosebumps. Also, the upright hairs do not provide an insulating layer for us. There simply aren’t enough air on a human’s body coats to protect us from cold. Clothing works many times better, and is also more socially accepted. So why do we get goosebumps?

In a new study, researchers have now discovered why we still get goosebumps. When you get goosebumps, the hairs on your chest, forearms and legs will stand up. This is caused by the contraction of muscles at the bottom of the hair follicle. By contracting the muscles, small dents are created in the skin, and the skin around the hair can be thus seen as little mountains. “The muscle that contracts to create goosebumps is needed for the connection between the nerve and the follicle stem cells (stem cells from the hair follicles, ed.),” explains Hsu. “So even if we don’t get goosebumps so often, we still need the same cells and the same anatomical compound behind goosebumps. We need the muscle to maintain the nerve in the skin. And we also need this nerve to regulate the follicle stem cells.”

An important connection

The interaction between the nerve and the muscle is also well known. This forms the cellular basis for goosebumps: the cold triggers neurons to send out a nerve signal and the muscle reacts to it by pulling together and leaving the hairs upright. But when the researchers took a closer look at the skin, they discovered that the nerve is not only connected to the muscle, but also forms a direct connection to follicle stem cells. In fact, the nerves wrap themselves like a ribbon around these stem cells. “This finding was very surprising and exciting,” says Hsu. “Neurons normally prefer connections to other irritable cells, such as other neurons or muscles with synapses. We were therefore very surprised when we discovered synapse-like connections between the nerve and a stem cell.”

Cold

The researchers also discovered how prolonged cold can bring the nerves into a higher state of alertness. “In cold, the nerve releases a lot more neurotransmitters,” explains Hsu. This causes short-term goosebumps. But if the cold persists, it can stimulate more hair growth in the long run. “In short, what we discovered was that the cells that cause goosebumps (the nerve and muscle) are also essential for regulating the stem cells, which regenerate the hair follicle and hair.”

The hair follicles, stem cells and nerves actually form a closed circle that need each other. The nerve is the signal component that activates the stem cells via neurotransmitters, while the muscle is the structural component through which the nerve fibers can make direct contact with the follicle stem cells.

The researchers confirmed in later experiments that the muscle is indeed an essential link between the nerves and the follicle stem cells. When they removed the muscle that was connected to the hair follicles, the nerve also retreated and the connection to the follicle stem cells was lost.

Thanks to the study, we now finally know why we are still getting goosebumps. But why did it take us so long to figure out the reason behind something as ordinary as goosebumps? “There are many common phenomena whose underlying biological basis we still do not understand,” Hsu says when asked. “Getting goosebumps is just one example. As a scientist, I think it’s always very satisfying to take a common phenomenon, conduct rigorous experiments and let science speak for itself. Our study allowed us to look at goosebumps a little differently. We not only considered it a reaction, but found that there are three tissues connected to each other: the follicle stem cells, muscles and hair follicles. Finally, we spent years building tools that allow us to study different cell types in the skin. Science is full of wonder. I think a curious mind is needed, along with determination and perseverance to pursue one’s curiosity.”

Although the researchers have now unraveled the secret behind getting goosebumps, some questions remain unanswered. For example, we not only get goosebumps from cold, but also, for example, when we are afraid, or hear a beautiful music. “We don’t know exactly what underlies this,” says Hsu. “That would be something very interesting to explore in the future.”

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