If someone were to run an ice cube across the back of your neck, chances are you’d get a piloerection. Fear not, nobody’s about to shame you. After all, goosebumps happen to everybody.
Thing is, why? After all, it’s hard to imagine a benefit to naked skin going all bobbly like that. The trick is to go into humans’ ancient past, as once upon a time we were hirsute af. Anyone with a cat will have seen how when they get a fright, they poof up like nobody’s business. It’s hilarious in a little ragdoll called Muffin but imagine the same effect on a wildcat and you can see how it might be pretty terrifying.
Goosebumps as an evolutionary advantage
Back when our ape ancestors were still very hairy, they used a similar defence when trying to scare off predators. The trait is still seen among some of our closest relatives, such as chimpanzees. According to the Chimpanzee Sanctuary Northwest, chimps are "pilo erect when his or her hair is standing on end due to anxiety or excitement. Humans also experience piloerection when we get goosebumps, but it’s not as obvious since we have less hair.”
Goosebumps are, therefore, a vestigial reflex with regards to scaring off predators. A kind of evolutionary hangover that no longer serves its original purpose, but some have argued that our spontaneous skin bumps serve other useful functions.
Goosebumps were more effective when our ancestors had more hair.
Image credit: maik555 / Shutterstock
Goosebumps and hair growth
That ice cube that gave you a piloerection earlier did so because it triggered the body’s sympathetic nervous system, which coordinates and regulates our unconscious bodily functions. It’s this involuntary system that tells tiny smooth muscles under our skin called arrector pili to contract, making our hairs stand on end (though in some curious cases people can actually control their goosebumps, switching them on and off at will).
However, a 2020 study examined this mechanism in extremely high resolution and discovered that the sympathetic nerve fibers 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,” postdoctoral fellow at Harvard University and co-first author of the study, published in Cell, Yulia Shwartz, said. “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.”
"We discovered that the signal comes from the developing hair follicle itself. 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.”
As our understanding of the role of stem cells in the epidermis has grown, some have suggested that goosebumps could be the key to innovating better treatments for everything from hair loss to burn healing and certain cancers.
Goosebumps and our imagination
Some of us are more prone to getting goosebumps than others when imagining things or listening to music (aka, skin orgasms), and scientists have uncovered that this can come down to having a unique brain. A 2016 study found that people who get a shiver up their spine have more fibers connecting their auditory cortex to brain areas associated with emotional processing. This lets the two areas communicate better and means that people who get the chills experience intense emotions differently from those who don’t.
Neurologist Adam Zeman, author of The Shape Of Things Unseen: A New Science Of Imagination, knows all about the physical changes that can be triggered by our imagination. When asked for a favorite example in an interview with IFLScience's CURIOUS magazine, he said:
“A remarkable brain imaging study by Anne Blood and Robert Zatorre examined, precisely, goosebumps! They asked musicians to identify passages of music that reliably gave them shivers down the spine – these are quite reliable for a given individual but differ between individuals."
"They compared brain activity while listening to shiver-provoking and neutral passages, showing that shivery music is associated with strong activation of a network of deep brain areas linked to rewarding activities generally, from chocolate to sex. Locating the source of such an evanescent – even if intense – experience in the brain was a tour de force.”
Given all that goosebumps have given us, evolutionary hangover seems a bit mean for the little lumps that accompany some of our most profound and moving experiences. If only they were named after something with a little more dignity than a goose.