You’ve probably experienced goose bumps either from feeling creeped out watching a scary film or being met with a cool breeze. The scientific name for this is ‘cutis anserina’ though some might wonder why the name ‘Goose bumps’ is used. As the hairs of your arms or neck come to a stand, the hair follicle is raised causing tiny bumps in the skin surface which happen to resemble the skin of a goose (or any bird, really) when its feathers are plucked.
Think back to a time when you’ve gotten that tingly feeling down your spine - maybe it was listening to an old song with a certain memory behind it or feeling frightened or nervous before riding a roller coaster. Fear, excitement and nostalgia are just some of the emotions which can trigger goose bumps. It’s strange that this physical response that is so linked in with our emotions actually has understandable science behind it.
The erection of the hairs on your arm and neck is involuntary, meaning that you can’t control it. The contraction of arrector pili muscles found connected to the hair follicles in mammals are responsible. Piloerection (when hair is made to stand) is controlled by the Sympathetic Nervous System, which is core to the ‘fight-or-flight’ reaction we get when we are panicked or under stress. The adrenaline released causes the arrector pili muscles in the hair follicles of the arms and neck to contract leading to the raised bumps and hairs.
This response doesn’t seem to be very useful in humans. However, it is thought that our ancestors had this same response, but they were known to be covered with much more hair. Over time we have evolved to have much less hair, but this response to certain stimuli has remained. The purpose of piloerection in our ancestors was to raise hair to make them appear larger in a situation where they would need to defend themselves - linking to the primal response of ‘fight-or-flight’. This is seen today in animals such as porcupines. Luckily we don’t have to face many scary predators anymore and so the need to appear larger isn’t there, but this vestigial response remains and it’s not quite known why.
Another reason for piloerection ties in with body homeostasis (maintaining a constant internal environment) and the need to maintain a suitable temperature in order to ensure bodily processes can carry on in their optimal conditions. In suddenly cool temperatures, hair stands up via contraction of the arrector pili muscles causing air to be trapped between the hairs, thus acting as an insulator. This action traps heat, leading to a more suitable body temperature - which is very important. Again, this doesn’t make a lot of sense in humans since we haven’t got nearly enough hair for this to be useful for heat loss prevention, but in our ancestors or other mammals with thick coats of fur, this would have been much more effective.
All in all, goose bumps seem like a useless response when we’re cold or something captivates our emotions, but once upon a time they served as a primal response that came in handy for our ancestors. If you do get them (and you probably will) don't worry as they’re temporary and normally go on their own when the body calms down or warms up a bit.