Goosebumps are one of many evolutionary leftovers from our ancestors. Long ago, hairier animals used to plump up their skin hair to appear larger and scare off predators – something we don’t need to do so much now.
Yet we still experience goosebumps in response to rapid temperature changes (although we don’t benefit much from this reaction) and some of us when listening to music. However, an international team of researchers have uncovered another reason for this preserved feature – the regeneration of hair growth.
Skin is our body’s boundary with the outside world, so it’s no wonder that it reacts to changing conditions. For years, scientists have known that in response to an unexpected cool breeze the body’s sympathetic nervous system (which coordinates and regulates our unconscious bodily functions) will cause a tiny smooth muscle underneath our skin to contract and form goosebumps. The raised hairs then help to trap an endothermic layer of heat.
But after examining this mechanism in extremely high resolution, the researchers discovered that the sympathetic nerve fibres were also wrapped like a ribbon around hair follicle stem cells (which produce hair throughout a person’s lifetime). During a prolonged cold period, they found that the nerve activity increased and triggered the stem cells to regenerate the hair follicle and grow new hair.
“It's a two-layer response: goosebumps are a quick way to provide some sort of relief in the short term. But when the cold lasts, this becomes a nice mechanism for the stem cells to know it's maybe time to regenerate new hair coat,” Yulia Shwartz, postdoctoral fellow at Harvard University and co-first author of the study published in Cell, said in a statement.
When Shwartz and her colleagues took a deeper dive into the mechanism, they realized that if they removed the muscle responsible for goosebumps from the situation, the hair regeneration process couldn’t take place. The trio of nerve, muscle and hair follicle stem cells are caught in complex relationship that results in goosebumps and hair growth.
"We discovered that the signal comes from the developing hair follicle itself,” Shwartz explained. “It secretes a protein that regulates the formation of the smooth muscle, which then attracts the sympathetic nerve. Then in the adult, the interaction turns around, with the nerve and muscle together regulating the hair follicle stem cells to regenerate the new hair follicle. It's closing the whole circle.”
Shwartz and the team plan to continue their research into how the external environment may influence other stem cells in the skin. In the meantime, you can watch someone with superpowers (albeit a pretty lame one) consciously give themselves goosebumps on cue. Take that Marvel.