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You might have a beard, or a moustache, or even a soul patch. What you don't have are whiskers.

Hosted by: Hank Green

SciShow Talk Show with Dr. Amanda Duley:
https://www.youtube.com/watch?v=OMEk6z4l6aY
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Sources:
https://www.thenakedscientists.com/articles/questions/human-facial-hair-cats-whiskers
http://jeb.biologists.org/content/220/2/133.1
https://www.theatlantic.com/science/archive/2015/10/seals-use-their-whiskers-to-see-and-hear/413269/
http://onlinelibrary.wiley.com/doi/10.1002/ar.a.20273/abstract
http://advances.sciencemag.org/content/2/8/e1600716.full
http://rstb.royalsocietypublishing.org/content/366/1581/3037
http://onlinelibrary.wiley.com/doi/10.1002/ca.20497/abstract
https://link.springer.com/article/10.1007/s12565-012-0133-2
http://www.sciencedirect.com/science/article/pii/S0047248410000400
http://www.nature.com/nature/journal/v471/n7337/full/nature09774.html
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0084258
http://www.pnas.org/content/103/44/16544.full
http://www.sciencedirect.com/science/article/pii/S0960982214006010
http://www.nature.com/articles/srep25604
http://www.scholarpedia.org/article/Whisking_kinematics
http://jn.physiology.org/content/89/1/104.long
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Images:
https://commons.wikimedia.org/wiki/File:Schimpanse_Zoo_Leipzig.jpg
https://commons.wikimedia.org/wiki/File:54986main_mouse_med.jpg
https://commons.wikimedia.org/wiki/File:2005_RUSSIA_Ozernoy_Gulf_0121_small.jpg
https://commons.wikimedia.org/wiki/File:Etruscan_Shrew_(Suncus_etruscus)_04.jpg
Whether you’ve got a big ol’ lumberjack beard or a pencil-thin mustache, if you have facial hair, you might refer to it as your “whiskers.” But that is not what they are.

The fact is, humans don’t have whiskers. True whiskers—like those on your dog or cat—are far more special than any human facial hair.

Whiskers are acutely sensitive and can help creatures hunt, sense the direction of the wind, and find their way around in the dark. In fact, they are so useful, nearly all mammals have them… we’re just one of the rare exceptions. So, what makes whiskers different from the stubble on your chin?

Well, whiskers are what scientists call vibrissae. And they are similar to regular hair ... they’re made out of the same protein, keratin. But whiskers are usually thicker, stiffer, and more importantly, they grow out of completely different kinds of follicles than your hairs do.

The follicles for vibrissae are deep in the skin, and they’re surrounded by pockets of blood, which are connected to nerves. Researchers think that these pockets of blood help amplify any vibrations that come through the hairs to help make them extra-sensitive to touch. And the nerves, of course, lead up to the brain, where huge sections of the somatosensory cortex are devoted to making sense of all the tactile information that the whiskers are picking up.

Now, whiskers can be found anywhere on an animal’s body, but the most common spot is on the face, especially around the mouth or eyes, where they come in two main types. The long hairs we usually think of as “whiskers” are called macrovibrissae, and they can be moved voluntarily. But there are also shorter, stubbier whiskers, usually right under the nose, called microvibrissae.

Many animals, like rats or mice, have both kinds. And in those creatures, it’s thought that the big ones are used for spatial tasks, while the little ones are more important for recognizing certain objects. If you can move your big whiskers, like a rat does, you can actually get lots of really valuable information about the space around you ... almost like seeing, but with your hair.

This behavior actually has a name—aptly enough, it’s called whisking. For example, if a rat is new to an area, it will move slowly, flicking its whiskers back and forth, letting them sweep over a broad area to get a good sense of the surroundings. But if a rat already knows the space, it will move more quickly, and whisk over a smaller area just to make sure it doesn’t run into anything.

And if a rodent is especially interested in something, it will increase the speed of its whisking to get a higher resolution sense of what the thing is. Other animals use their whiskers for more nefarious purposes… at least, if you’re a prey animal. The tiny Etruscan shrew, for example, uses its whiskers to find and capture insects nearly as large as itself, even inside dark tunnels.

Seals, too, use the tactile hairs to hunt, and have whiskers so sensitive that they can actually sense fish breathing. Biologists think that’s because seals have as much as ten times the number of nerve endings per whisker follicle that land animals have. OK, so you get that whiskers are super-useful, and on the right animal, they can be downright dashing.

So in that case, why don’t we have them? Well, we probably did at one point. Or, at least, our ancestors did.

Whiskers are thought to have been an important adaptation in early mammals, including primates. But then, around 800,000 years ago, we appear to have lost the bit of DNA that allows for true whiskers. However, our distant cousins—the other great apes—still have it, and you can see their whiskers if you look closely.

They are not the big flashy whiskers your cat has, but chimps, gorillas, and orangutans all have microvibrissae all around their mouths and eyebrows. There’s even evidence that some people today have vestigial muscles in their upper lips that are leftover from when our primate ancestors had whiskers— although, not all scientists are convinced about that. Either way, modern humans seem to have gotten along just fine without whiskers.

All that brain space that was dedicated to getting information from whiskers is now used to map our sense of touch, with a big chunk going to our fingertips. And we have pretty good visual systems for navigating, so we don’t have to feel our way around with hairs. So, if you’re wishing you could go out for a nice whisking, or had a sweet set of whiskers that could make you into like a real-life Daredevil, take heart.

Not having them is part of what makes you human. But if you want to see me rocking some scientific cat ears, check out our Talk Show about the brain with Dr. Amanda Duley.

There’s a link in the description. I move them with my mind.