Fadime Pala
Scottsdale, Arizona
The “goosebumps reflex” is a fascinating living evidence of evolution, a mechanism inherited from millions of years when the ancestors of humans were far hairier than today’s humans. Then, as today, they had at the base of every hair a tiny smooth muscle called the arrector pili muscle, which contracted involuntarily under the control of the sympathetic system when they became cold or frightened. (The term arrector comes from Latin, meaning “to raise,” while pili means “hair.”)
We never consciously feel this muscle and cannot voluntarily control it, and many people go through life without ever realizing it exists. But in some people, when they feel cold, the hypothalamus detects the change and activates the sympathetic nervous system, which causes the arrector pili muscles to contract, the hair stands upright, and trap a thin layer of air, reduce heat loss from the body. This mechanism is remarkably effective in cats, dogs, chimpanzees, and in the ancestors of humans. In modern humans, however, this mechanism is on the whole unnecessary because evolution and sexual selection have favored individuals with less body hair and enhanced effectiveness of sweating. Yet goosebumps still occur, because evolution does not fully erase every trait, and the phenomenon occurs not only in the cold but also when we are frightened, emotionally moved, deeply inspired, or listening to a powerful piece of music, all instances when the sympathetic system can become activated.
This is why we can experience goosebumps during a horror movie, an emotional scene, or a breathtaking symphony. In scientific terminology, this response is known as piloerection, while in everyday English we simply call it goosebumps. From a scientific perspective, this reflex contributes very little to heat conservation in modern humans. Nevertheless, its physiological mechanism remains fully functional, illustrating the remarkable coordination between the hypothalamus, the sympathetic nervous system, and the arrector pili muscles.
FADIME PALA is a writer with a background in nursing, pathology, and theatre. She currently serves as a research professional at Mayo Clinic, where she contributes to translational oncology research in pathology and histology within the Patient Inspired Engineering Laboratory. Her writing explores the intersections of medicine, pathology, history, philosophy, and the medical humanities, with a particular interest in the lived experience of illness, healing, and human connection.