Have you ever wondered why, when you get cold, the flesh on your arms and legs erupts into a sea of tiny bumps?
The answer is simple: to keep you warmer.
Okay, so the answer isn’t really that simple. Mostly because, as you may have noticed, it doesn’t exactly feel like you’ve put on a wool sweater when you get goosebumps.
Goosebumps are a “vestigial” action. The term “vestigial” comes from “vestige,” which comes from the Latin vestigium, meaning “footprint” or “trace.” It also refers to “a mark” or “a sign.” Merriam-Webster defines vestigial as: a bodily part or organ that is small and degenerate or imperfectly developed in comparison to one more fully developed in an earlier stage of the individual, in a past generation, or in closely related forms.
The reaction is physiological: arousal (like irritation or excitement, fueled by adrenaline) or low temperatures cause the muscles around our hair follicles to contract, forming small bumps over broad surfaces of flesh. They’re called “goosebumps” because, after the feathers have been plucked out, naked poultry and a goosebumped human look fairly similar. Well except for the beak and wings and stuff.
So what we’re talking about here are body parts and physiological or psychological behaviors that we have but no longer utilize to the fullest. Many generations ago they served some greater purpose to us, but now they linger on until they evolve away.
So back to goosebumps: when you’re cold, those little muscle contractions, called “piloerections,” make our hairs stand on end. In the old days, when we were really tree-huggers, we had a lot more hair and it was significantly thicker. When you’re hairy (or feathery!) and cold, that hair (or those feathers) will trap a substantial amount of heat if it’s standing away from the body.
Sometimes when we get scared, the goosebumps also appear. This response at least partially stems from the fact that mammals look bigger when their hair is standing on end. Like this cute little kitteh. Looking bigger could scare away a potential predator or rival, lending to survival.
Chimpanzees do it too. If we were still as hairy as chimps, we’d look pretty scary with a good rush of goosebumps. (As a sidenote, Save the Chimps says, “We share approximately 98% of our DNA with chimps, so it’s fair to say that we are 98% chimpanzee, and chimps are 98% human.” Awesome perspective.)
We still get goosebumps because there hasn’t been enough “selective pressure” to evolve away the reaction completely. That means there hasn’t been any negative effect on how humans reproduce based on having goosebumps this late in our evolutionary lives. So even though we evolved to have an almost completely useless amount of body hair, the muscle response is still around.
Other vestigial parts in humans include the appendix and wisdom teeth. The tailbone, or coccyx, is another example, but the tailbone actually has muscle and other important attachments that we couldn’t do as easily without. (To be fair, the appendix appears to serve a very cool function, according to a study by Duke University Medical Center: it houses good bacteria that can repopulate the intestines when illness wipes out all the bacteria currently living there.)
On our very own bodies are signs of our history as a species. Despite the hundreds of thousands of years that we’ve been wearing animal skins (or cotton!), our hairs still stand on end when we’re cold. We still have partials tails, and some of us still grow extra teeth for all the vegetation we won’t be chewing.
This concludes our Evolution Awesomeness series – I hope you’ve enjoyed reading and learned something too! Before you go, check out this list of LiveScience’s Top 10 Useless Limbs (and Other Vestigial Organs) for more vestigial fun!
A great summary of why humans get goosebumps, by Scientific American.
Some great human origins/evolution articles by the Smithsonian Institution.
A news article about a captive chimp that throws stones – literally – at tourists, and appears to exhibit forethought by caching piles of stones around his enclosure.
Great little article on wisdom teeth.
…anyone remember the Goosebumps series by R.L. Stein? I was totally stuck on those as a kid!