I think it is safe to say that we have all had Goosebumps many times in our lifetime. They pop up all over our body when we get cold, but while it is a naturally and relatively common thing, do you even know what they are?
Properly known as piloerection, horripliation or pilomotor reflex, the bumps we get are stimulated by fear and cold and they are essentially just a temporary change in the skin. These stimulants cause a nerve discharge from the sympathetic nervous system (which is an involuntary portion of nerves we have) and the nerve discharges create muscle contractions called arrrectores pilorum that raise the hair follicles in our skin. It is the elevation of the hair that causes the Goosebumps. The name Goosebumps actually comes from the fact that plucked goose feathers resemble the human hair follicles.
We cannot control Goosebumps at all (hence the statement before that they are triggered by a involuntary nervous system) and they are also considered a fight or flight response. A fight or flight response is just a physiologic response that is our bodies primitive and automatic response that either prepares us to fight or flee (AKA flight) from any harm or fight off something, like an enemy or the cold. This leads right into some of the theories for why we get Goosebumps because the reason we get them is still uncertain. Biologists believe that they are a reflex that we developed years and years ago. One theory about Goosebumps suggests that our ancestors, who were much hairy than we are today, appeared bigger and scarier when they had goose bumps, therefore Goosebumps were useful for scaring away enemies. That theory goes hand in hand with the "fight" part of a fight or flight response. In terms of the "flight" part, Goosebumps could have also been used to keep people warm by making body hair fluffy and able to trap heat near the skin.
Our body today as we all know, still creates these muscle contractions as an attempt to warm us when we are cold, but with us being less hairy then our ancestors, our goose bumps are pretty ineffective at keeping us warm or helping scare off enemies. Essentially, Goosebumps are useless.
Researchers have tried looking into why we might get Goosebumps from music. Jaak Panksepp, a Bowling Green State neurobiologist studied how music triggers Goosebumps. He discovered that people got Goosebumps from sad feelings they get from music. Panksepp believes that chemicals in the brain, related to social loss, are the reason we get Goosebumps from sad songs. Pankseepp also suggests that this response is related to our ancestors reacting to the loss of a family member or the cry of a baby. So once again, our ancestor's reactions are affecting us today.
Goosebumps not only happen to us, but they also can pop up on animals. Ever see the hair on the back of a cat stand up? Or the needles of a porcupine stick out in an intimidating way? It is all the same as us. Goosebumps are happening as a body's attempt to stay warm or scare off an enemy. The difference is animals have much more hair, therefore Goosebumps work more for them than they do for us.
So next time you get Goosebumps, think about them and how they used to serve a purpose!