A microscopic view of hair.
Courtesy of Sandy Koch
The hair on our heads is on our minds. We have fun with follicles and learn about how they make hair. Our experts help us decipher what makes hair black or brown, blonde or red, and even why it turns gray. From eye lashes to ear and nose hair, this episode has it all. Why do humans have hair and not fur? Why is there hair on the top of our heads? How does hair grow? How does hair become curly or straight?
Plus: A brand new Moment of Um answers the question: "Why does my dad get fuzz in his belly button?"
This episode originally published on May 31, 2016. You can listen to the original version here:
The how's and why's of hair
by MPRAudio Transcript
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INTERVIEWER 1: You're listening to Brains On.
INTERVIEWER 2: Where we're serious about being curious.
INTERVIEWER 3: Brains On is supported in part by a grant from the National Science Foundation.
[MUSIC PLAYING]
MOLLY BLOOM: What is your favorite thing about your hair?
ALEX HARRIS: How smooth it is.
KATE HARRIS: Where I can just comb it back and then go do whatever.
MOLLY BLOOM: I have really curly hair, which I used to not like at all when I was your age. But now I like that I don't have to do anything to it, and it can just do its own thing. And whether you love your hair or just want to shave it all off, we're going to show you today how complex and cool it really is.
ALEX AND KATE HARRIS: Keep listening.
MOLLY BLOOM: You're listening to Brains On from American Public Media. I'm Molly Bloom, and my co-hosts today are Kate and Alex from Plano, Texas.
KATE HARRIS: Hi.
ALEX HARRIS: Hello.
MOLLY BLOOM: And you two recently got a closer look at hair. You wrote into us and told us that you were looking at strands of hair under a microscope. What gave you the idea to check that out?
ALEX HARRIS: We just got a new microscope, so.
KATE HARRIS: We decided to peek at hair.
MOLLY BLOOM: And what did you see when you looked at the hair?
ALEX HARRIS: Well, my hair was-- it had like little black dots all over it.
KATE HARRIS: And mine only had one. And my mom's gray hair had a ginormous line through it.
MOLLY BLOOM: Interesting. And you guys both have brown hair, right? But it looked different under the microscope.
KATE HARRIS: Yeah.
ALEX HARRIS: Yes.
KATE HARRIS: Much different.
MOLLY BLOOM: And when you put the hair under the microscope, is there anything special you have to do to it first?
ALEX HARRIS: You have to adjust it, then do lighting.
KATE HARRIS: And then there's also slides that you have to put it in to make it stay.
MOLLY BLOOM: So you take the hair and put it on a slide. And then you put it under the microscope. And you can see what it looks like really close up.
ALEX HARRIS: It's really cool.
MOLLY BLOOM: That's awesome. Well a little later in the show, we're going to talk to a scientist who looks at hair under a very powerful microscope. But first, let's start with the basics. A little hair 101, if you will. Here's a question to get us growing-- I mean, going.
AYALANDIA: My name is Ayalanda. I'm eight years old. I live in Calgary, Alberta. My question is, what is hair made of, and why do humans have hair and not fur like animals do?
MOLLY BLOOM: We'll get to the second half of that question later. But first, what is hair anyway? Is it alive?
ALEX HARRIS: It grows, but it doesn't have nerves the way skin does. You can pinch it without pain.
KATE HARRIS: And it's pretty strong stuff. But how is it so bendy?
MOLLY BLOOM: We asked Dr. Shani Francis to help untangle these questions. She's a dermatologist and the director of the Hair Center of Excellence-- awesome title, by the way-- at NorthShore University Health System in Evanston, Illinois.
SHANI FRANCIS: Hair is basically protein, but it has a very complex structure in how the protein is arranged. It's very organized. So the best way to describe it is like a rope of string that has many smaller ropes that are twisted and braided together. If you take a piece of yarn, OK, and when you-- you know how the yarn comes, and then you can unravel it and you see little smaller pieces of string.
Think about that, but amplify that and maybe take two or three or four, 30 pieces of string. And then coil those together in a rope. And that's how the structure of each hair fiber is. So basically it's pieces of string that have been twisted together. And then those twists have been twisted together. And then those twists have been twisted together. So you have just a big large rope. Very cool, and a lot of protein.
ALEX HARRIS: So each strand of hair is a collection of smaller strands, making the structure strong when it's pulled. But flexible when you bend it.
KATE HARRIS: Just like a rope.
MOLLY BLOOM: Here's another question we've gotten a lot.
ATTICUS: I'm Atticus, and I'm seven.
ELEANOR: Name is Eleanor.
ATTICUS: How does hair grow?
ELEANOR: How does hair grow?
KATE HARRIS: Hair growth starts with something called follicle. But wait, what's a follicle?
SHANI FRANCIS: Oh, hair follicles are everywhere. So everywhere you see a hair, you have a hair follicle. The hair itself comes out of this hair follicle, which is like a tube or a house tube that it lives in.
ALEX HARRIS: So follicles are basically tiny sacs in our skin where hair grows.
KATE HARRIS: They're lined with special cells that live in this follicle house.
[CHIRPING]
CELL 1: Ah, new day.
CELL 2: A glorious time to be a cell living in a hair follicle.
ALEX HARRIS: When they get a signal, they start their work.
[STEAM WHISTLE]
CELL 2: Oh, time to get cranking.
CELL 1: Yep. These hairs aren't going to grow themselves.
SHANI FRANCIS: And these cells rapidly divide.
[GRUNTS]
CELL 1: There we go. Two of me.
[GRUNTS]
[POPS]
CELL 2: Oh, hello, more of me.
SHANI FRANCIS: And as they are dividing, the old cells are getting pushed out of the way by the new cells.
CELL: It's getting crowded in there. Push those older me's out of here.
CELL: You got it. Move along other me's.
CELL: OK, OK, I'm leaving.
MOLLY BLOOM: As these older cells get pushed up the tube of the follicle, they leave behind all the blood vessels and nutrition keeping them alive.
ALEX HARRIS: They also get coated with special proteins known as keratin, making them tougher than living cells below.
SHANI FRANCIS: And so it's like an assembly line of hair cells moving up through this tubular house called a hair follicle. That's the reason why we think of hair fibers as dead, is because the part that's alive is the part that's dividing. And once it needs more space, it pushes the hair cells up. And that comes out as hair.
KATE HARRIS: Your hair growth has a few different cycles to it. First, there's the growth stage we just talked about.
ALEX HARRIS: It's called the anagen stage.
MOLLY BLOOM: During this phase, hair grows about half an inch a month, or six inches a year.
SHANI FRANCIS: The anagen part of the hair cycle lasts usually two to six years in most people. And most of our hairs are under this part of the hair cycle.
MOLLY BLOOM: After the anagen comes the catagen phase.
KATE HARRIS: During this period, hair growth stops. It lasts about 10 days.
ALEX HARRIS: Then the hair starts the final phase, known as the telogen stage. This one, the follicle takes a break from all its work.
[STEAM WHISTLE]
CELL 2: Phew, what a day. Feels like I've been working for at least six years straight.
CELL 1: Totally. I need a nap.
SHANI FRANCIS: And so in the resting phase, the hair is not growing. It's just sitting there. And at the end of the resting phase, which normally lasts two to three months, that hair is pushed out, and the cycle starts all over again. It's actually interesting, it's pushed out by new hair that's coming up.
[STEAM WHISTLE]
CELL 1: What a glorious day to be a cell living in a follicle.
CELL 2: Indeed. Time to get back to work. Hey, what's that old hair doing sitting there?
CELL 1: Oh, that was from the last shift, remember? Let's crank out a new hair to push it away.
CELL 2: You got it. Time to divide. Here we go again.
[GRUNTING]
[POPS]
KATE HARRIS: When old hires are pushed out by new hairs, you shed.
ALEX HARRIS: Don't worry, it's totally normal.
MOLLY BLOOM: In fact, most people lose anywhere from 50 to 150 hairs every day.
KATE HARRIS: But you've got thousands on your head, so it's hard to notice the difference.
MOLLY BLOOM: Before we start counting all those hairs on our head, we have another challenge for you. It's time for the mystery sound.
[MYSTERY SOUND CUE]
AUDIO TRACK: Mystery sound.
MOLLY BLOOM: Here it is.
[KNOCKING]
Any guesses?
ALEX HARRIS: I think it might be someone maybe tapping on glass or hammering.
KATE HARRIS: I think it's a hammer tapping on wood.
MOLLY BLOOM: Those are both really good guesses. We're going to be back with the answer a little bit later in the show.
AUDIO TRACK: Brains On!
MOLLY BLOOM: So far we've learned how hair grows, but now it's time to get into the why, as posed by Ayalanda earlier.
AYALANDA: Why do humans have hair and not fur like animals do?
MOLLY BLOOM: And Imogen.
IMOGEN: My name is Imogen Tree, and I'm six years old and from Newbury in the UK. My question is, why do we have hair?
KATE HARRIS: So to find out, we talk to Sandy Cook.
ALEX HARRIS: She studies the evolutionary biology of hair at Penn State University.
KATE HARRIS: Before she started selling hair, she did forensic analysis of hair for the FBI.
MOLLY BLOOM: For starters, Kate and Alex asked Sandy about the hair that they looked at under the microscope.
ALEX HARRIS: We saw by hair had a lot of black dots through it.
KATE HARRIS: And mine did not have. It only had one. And my mom had a black line through it.
SANDY COOK: If you think of a hair like structurally, it's going to be very similar to a pencil. So how a pencil has the paint covering the wood covering the lead, a hair has an outer cuticle layer, which is a very thin protective layer. And then there's the cortex of the hair. And that's where all the pigment granules are.
And then running through the center of the hair is called medulla. And that can be a dark black structure. And it can be completely present, like a line. It can be broken up and here and there. Or it could be absent. And it is a feature that we use when we do a microscopic comparison. So you were definitely seeing a lot of what we see when we look at hairs under a microscope.
With humans, we can tell general differences in ancestry. If a hair has been artificially treated, so if it's been dyed or bleached, we can tell. We can tell if there's been any damage to the hair. And there are differences that can be identified between people. But there's also variation within our own hairs so if you look at yourself in the mirror, you might see some slight variation in color, in length, and just some natural highlights.
And that's going to also appear microscopically. There's going to be some differences in the distribution of pigment. And there's going to be a range of characteristics.
ALEX HARRIS: Why do humans have hair, not fur?
SANDY COOK: Well, hair and fur are actually made of the same protein called keratin. And they're chemically the same. If you think about animals, we tend to think of our pets, dogs and cats, and they have fur all over their bodies. While humans, we have five million hair follicles on our bodies. But only about 100,000 to 150,000 of those are on the top of our head.
So we have hair all over our bodies. It's just in a much more reduced form. So if you look at your arms, you can really see very fine hairs. And that's our equivalent to fur. I think there are several theories about why humans may have reduced body hair, and that really relates to when our human ancestors started walking upright. One of the hypotheses are thoughts about why early humans may have not needed as much hair protection or fur coat on the whole body was that once they started walking on two feet, they really needed to be able to evaporate more of their body heat through sweating.
But there's still a definite need for protection from the Sun's rays on the top of a person's head so that we retained the head hair far more than we did our body hair.
MOLLY BLOOM: Well, thank you so much, Sandy, for being here today.
ALEX HARRIS: Thank you.
KATE HARRIS: Thank you.
SANDY COOK: You're welcome. And Kate and Alex, I hope you really enjoyed studying hairs and find out more. Bye-bye.
KATE HARRIS: Bye, Sandy.
[MUSIC PLAYING]
ALEX HARRIS: Do you have a question you want to hear on Brains On?
KATE HARRIS: Or a mystery sound share?
ALEX HARRIS: Or do you want to send us a high five?
MOLLY BLOOM: You can do that at brainson.org/contact. That's where we got this excellent question.
IAN: My name is Ian from Seoul, South Korea. My dad has been getting fuzz in his belly button. My question is, where is it coming from, and why don't I have fuzz in my belly button?
MOLLY BLOOM: We'll have an answer to that during our Moment of Um at the end of the show. And we'll read the most recent names to be added to the Brains Honor Roll. And hey--
[GROANS]
That sound means we made a mistake. In last week's Moment of Um, we said blood is blue when it doesn't have oxygen in it. But that's not true. Blood is always red. Red, red, red. It just looks blue in our veins because of the way light is reflected as it goes through our skin. So there you go. We made a mistake, but we corrected it. You can go listen to the updated answer in last week's episode, Why are Smartphones so Hard to Put Down?
[GROANS]
That made us feel sheepish. But we're all about talking feelings these days, because we're working on a series about emotions. And we want to hear from you, our listeners. We want to know what your body feels like when you're happy, or sad, or angry, or nervous. Pick one of those feelings and tell us how it makes your body feel. Send your answers to us at brainson.org/contact. Thanks, and keep listening.
[MUSIC PLAYING]
MOLLY BLOOM: You're listening to Brains On.
ALEX HARRIS: I'm Alex Harris.
KATE HARRIS: And I'm Kate Harris.
MOLLY BLOOM: And I'm Molly Bloom. Today, hair is on our heads and on our minds.
KATE HARRIS: And lots of people have written in with questions about hair.
ALEX HARRIS: So let's get right down to the answers.
WILSON: My name is Wilson, and my question is, why are some hairs different colors?
BEN: My name is Ben. What determines whether a hair is curly or straight?
MOLLY BLOOM: Excellent questions, as usual. Let's turn back to Dr. Shani Francis for the answers.
ALEX HARRIS: Starting with hair color.
SHANI FRANCIS: So pigment is what colors our hair. We have natural pigment in our hair. It's normally found in the middle of the hair follicle. So remember that shape of that rope of ropes? It's buried down in the middle. But sometimes in the darker hair, you can have it in the most outermost layer called the cuticle. The type of pigment in hair is called melanin.
And there are two different kinds of melanin. There's eumelanin, which is found in brown and black hair. And even skin. It's called eumelanin. And then there's pheomelanin, which is found in red hair and blonde hair. And this pigment is more yellowish-red.
MOLLY BLOOM: So your hair color is determined by how much eumelanin or pheomelanin you have in each strand.
ALEX HARRIS: People with dark black hair have more eumelanin.
KATE HARRIS: Light brown hair has less.
MOLLY BLOOM: Redheads have a lot of pheomelanin.
ALEX HARRIS: Blondes, not as much.
KATE HARRIS: What about gray hair?
SHANI FRANCIS: I like to explain it that the cells that are making the pigment are very closely related to that hair follicle. And so they throw in a little pigment on the hair follicle as it's rapidly dividing.
CELL: Adding pigment, always adding pigment. Making colors. I love adding pigment. Pigment, pigment, pigment--
SHANI FRANCIS: Those cells get tired, like all cells in our body as we age. And when they get tired, they burn out.
CELL: Adding pigment. Always adding pigment. You know what? I quit.
SHANI FRANCIS: And when they burn out, they stop producing pigment. And so if there's no pigment coming out of that cell, then there'll be no pigment in the hair follicle and there'll be no pigment in the hair.
ALEX HARRIS: OK, so that's color. But what about curls and waves and all the other textures of hair we have?
MOLLY BLOOM: Shani says it mostly comes from the shape of the follicle.
KATE HARRIS: You know, the house the hair lives in.
SHANI FRANCIS: And the shape of that hair follicle differs in different people. And so if that hair follicle or that tube that the hair is coming out of is more circular-- and really I mean like a perfect circle-- that hair will be straight. If that hair follicle house is oval, then you will see a curly hair coming from there. And the tightest, tightest curls, the kinkiest hair, is an extreme curly. And that shape of that house is more ellipsoidal. So like an exaggerated oval.
MOLLY BLOOM: Both your hair color and its texture are influenced by your genetics, or the genes you get from your parents. So you can thank them for whatever's growing on top of your head.
ALEX HARRIS: The hair on top of our heads has really been the focus so far. But that's not the only hair we have up there.
KATE HARRIS: We've got eyebrows, eyelashes, nose hair. All of it serves a purpose.
MOLLY BLOOM: We asked our friend Sanden Totten to break it all down for us.
SANDEN TOTTEN: The hair on and in our faces is super important stuff. I mean, it's there for a reason, right? Take Bob, for example.
BOB: Me again?
SANDEN TOTTEN: He's got hair above his eyes, around the lids, hair in his nose and in his ears.
BOB: I do. Huh, that's a lot of hair.
SANDEN TOTTEN: But what if we took some of it away? Like say we wax off his eyebrows.
BOB: Ow! That hurt.
SANDEN TOTTEN: And let's say we stuck Bob on a treadmill. You know, for science.
BOB: Oh man. Running? I shouldn't have eaten that sandwich right before this, huh?
SANDEN TOTTEN: Normally when we sweat or if it rains, that moisture will trickle down our foreheads toward our eyes. Eyebrows help divert those liquids to the side of the face. So it doesn't get in our eyes and we can still see. But without eyebrows--
BOB: Oh man. So-- so much sweat. My eyes. Oh, it stings. Ow.
SANDEN TOTTEN: And while Bob is busy trying to wipe the sweat from his eyes--
BOB: Ow! Anyone have an extra set of eyebrows I can borrow? Anyone? I hate exercise.
SANDEN TOTTEN: Next, let's imagine what would happen if we took away Bob's eyelashes.
BOB: I barely use those. I doubt I'll notice.
SANDEN TOTTEN: Eyelashes also help divert moisture. And when you squint, they shield your eyes from strong light, like the Sun. Like the brim of a baseball hat.
BOB: Now that you mention it, it is awfully bright all of a sudden. And my eyeballs are so dry and itchy. I can't stop rubbing them.
SANDEN TOTTEN: That's because lashes help block small particles, and even bugs from getting in your eyes. Scientists have also found that eyelashes help reduce wind flow across the eyeballs. That, too, keeps them clean from dust and prevents them from drying out too much.
BOB: My eyes feel like the Sahara Desert.
SANDEN TOTTEN: So that's two really important types of hair to help protect your eyes. But what about nose hair? It's not on your face, so it's not diverting sweat or shielding you from sunlight.
BOB: Yeah. Plus, it's just gross. Go ahead and get rid of it. Who needs it? Nose hair, I don't care. Nose hair--
SANDEN TOTTEN: But Bob should care.
BOB: Nose hair, I don't care-- hm?
SANDEN TOTTEN: Even though it's not glamorous, nasal hair is super important. Say we pluck out Bob's nose hair.
BOB: Plop?
[PINCHING]
Ow! Yow! Oh!
SANDEN TOTTEN: Now when he takes a big whiff of air--
[BIG INHALE]
--particles of dirt, pollen, and even germs have an easier time getting through his nose and into his body.
[COUGHS]
That's not good for his breathing or his health. Nose hair is like a built-in air filter. Ear hair does something similar.
BOB: Wait. I have hair in my ears, too?
SANDEN TOTTEN: Yes, Bob. We all do. But adults tend to have a lot more of it. It also helps filter dirt and dust. And without the hair in your ear, that fly buzzing around Bob's head might have an easier time getting stuck in his ear canal.
BOB: It's loud. Ow And it tickles.
[CHUCKLES]
This is a very strange sensation.
SANDEN TOTTEN: So clearly, the hair in and on our heads is useful stuff. So let's put Bob back the way he was.
BOB: Let's see. I have my eyebrows, thank goodness. And my eyelashes. So glad to see those. Ear hair, check. Nose hair? I think you gave me too much nose hair.
SANDEN TOTTEN: Sorry, Bob. That's the way we found you.
BOB: I should really trim these. It's like a forest in here. Why didn't anyone tell me?
SANDEN TOTTEN: So be thankful for the hair you've got. It's pretty neat stuff. And Bob, while you're at it, you might want to take a look at your ear hair, too. OK, back to you, Molly, Kate, and Alex.
KATE HARRIS: Thanks, Sanden!
[VOCALIZING]
AUDIO TRACK: Brains On.
MOLLY BLOOM: I know waiting has made your hair stand on end. So let's get back to the mystery sound. Let's hear it again.
[KNOCKING]
Any other guesses?
ALEX HARRIS: I still think-- maybe it's a hammer banging on a coffee table?
MOLLY BLOOM: So what do you guys think that might have to do with hair?
ALEX HARRIS: I'm not sure.
KATE HARRIS: Neither am I.
MOLLY BLOOM: Well, here with the answer is Shane Price.
SHANE PRICE: That was the sound of the hair board.
[LAUGHS]
We have no name for it right now, so that's the best thing that-- that's what we refer to it as here in the office. The hair board. The hair fiber board, something like that. Yeah.
KATE HARRIS: What's the hair board?
MOLLY BLOOM: What do you think it might be?
KATE HARRIS: Maybe a board that you keep hair on?
ALEX HARRIS: Maybe you study on it.
MOLLY BLOOM: Very good guess. Well, let's have Shane tell us what it is.
SHANE PRICE: It's a grayish brown. It actually looks a little bit like marble. It's got a marbled appearance to it. It's made up of hair fiber. But it's all compressed into a board. So when you look at it, it looks like some sort of tile or a board-like material.
MOLLY BLOOM: Shane runs a company called Green Circle Salons. He works with hair salons all over Canada and the US to recycle products that come out of those shops. There's lots of plastic and glass and aluminum foil, and there's also lots of hair. So how do you turn hair into a board?
SHANE PRICE: We work with an engineer in Montreal. He's created a metal frame. So it's in the shape of the board that we'd like. And he'll lie the hair down in this frame. And he adds resin to the hair and then uses a compression machine to force it down and to compress it. The hair fibers are all overlapping and mixed together, and the resin fills in the space where there's air.
And then during the compression, you're squeezing out all of the air so you just have hair and resin. And over time, that will harden into a sheet or a board of hair.
MOLLY BLOOM: Shane hopes that his hair boards will be used as furniture and shelving in some of the very same salons that sent him the hair to begin with.
KATE HARRIS: That is really, really cool.
MOLLY BLOOM: Yeah. And that actually is not the first time that they've used recycled hair. How else do you think they could reuse hair?
ALEX HARRIS: For wigs.
KATE HARRIS: Dolls.
MOLLY BLOOM: They actually use it in a very unexpected way. They take hair and stuff it into old nylon stockings to make something that's called a hair boom. And Shane helps manufacture these hair booms to help clean up oil spills.
SHANE PRICE: This was discovered back when the Exxon Valdez oil spill happened in Alaska.
NEWS ANCHOR: It's not only the worst oil spill in US history, it's by far the largest in such a remote pristine area. The tanker, the Exxon Valdez, had just loaded more than a million barrels of Alaskan crude. It was about 25 miles from the Valdez terminal and was apparently trying to dodge ice flows from the nearby Columbia Glacier when it ran aground.
SHANE PRICE: One gentleman that happened to be a hairstylist from Huntsville, Alabama, was watching the news and notice that the otters' hair was actually picking up the oil that was on the water. And so he had an idea. Well, he wondered if he was to take human hair from his salon, if it would do the same thing. And he quickly discovered that it would. And in fact, it's a great absorbent of oil.
KATE HARRIS: That is really cool.
ALEX HARRIS: I never knew that.
KATE HARRIS: Yeah. I never even knew about the Alaskan crash.
MOLLY BLOOM: Yeah, that happened in 1989. And Shane says that every 500 grams of hair, which is a little over a pound, that pound of hair can soak up about one liter of oil. And that's about a quart or the size of a large milk carton. And hair booms can be reused about a hundred times. Hair is both useful on our head and when it's not.
[MUSIC PLAYING]
KATE HARRIS: Hair is basically a rope of protein.
MOLLY BLOOM: The color comes from cells in your follicles. And the shape of those follicles make your hair curly or straight.
ALEX HARRIS: All of that is ultimately determined by your genes.
KATE HARRIS: There are thousands of hairs on your head that are constantly in the cycle of growing and falling out.
MOLLY BLOOM: And our hair isn't just there to look Pretty
ALEX HARRIS: Looks are a part of it. But they're also there to protect us and regulate our body temperature.
MOLLY BLOOM: That's it for this episode of Brains On.
KATE HARRIS: This episode was produced by Marc Sanchez, Sanden Totten, and Molly Bloom.
ALEX HARRIS: With production help from Cristina Martinez, Craig Johnson, Alan Roberts, and Jackie Sojico.
MOLLY BLOOM: Many thanks to Melissa and Ryan Harris, Eric Wringham, Meg Martin, Peter Cox, Lauren Plow, Nicole Rogers, and Daniela Kruschinski.
ALEX HARRIS: And you can keep up with us on Instagram and Twitter.
KATE HARRIS: We're at @brains_on.
ALEX HARRIS: And we're on Facebook, too.
MOLLY BLOOM: Now, before we go, it's time for our Moment of Um.
AUDIO TRACK: Uh. Uh. Um. Um. Um. Um.
IAN: Hi. My name is Ian from Seoul, South Korea. My dad has been getting fuzz in his belly button. My question is, where is it coming from, and why don't I have fuzz in my belly button? Thank you for answering my question.
[MUSIC PLAYING]
JARED JAGDEO: That is such a great question. I think that maybe kids are just much more well taken care of than parents are sometimes in terms of kids usually have a parent watching them. And maybe no one's watching the dad.
[LAUGHS]
My name is Dr. Jared Jagdeo, and I am a skin doctor. Belly button fuzz is made out of dead skin cells that slough off, lint or cotton or whatever other fabric from our clothing and our environment, and combined with sweat and other bodily secretions that really get in there. So a little bit of moisture, a little bit of skin, and a little bit of stuff from your clothing.
Dads' belly buttons may sometimes be a little bit deeper than the belly buttons that children have. Children have very shallow belly buttons, so not much builds up there. The deeper the belly button, the more likely the fuzz will be in there. Hair can play a role in the accumulation of belly button fuzz, and dads have also had a much longer time to allow for some natural fibers from clothing to build on up there in that area.
Everyone's belly button of fuzz is unique to them, because it comprises the different fibers from the clothing that we wear and also our own personal DNA, such as from skin cells and also from other things that maybe we're in contact with.
MOLLY BLOOM: This list makes my heart warm and fuzzy. It's time for the Brains Honor Roll. These are the delightful humans who keep us going by sending us their ideas, questions, and mystery sounds. We love them.
[LISTING HONOR ROLL]
AUDIO TRACK: Brains Honor Roll. High fives.
MOLLY BLOOM: We'll be back soon with more answers to your questions.
ALEX AND KATE: Thanks for listening.
INTERVIEWER 2: Where we're serious about being curious.
INTERVIEWER 3: Brains On is supported in part by a grant from the National Science Foundation.
[MUSIC PLAYING]
MOLLY BLOOM: What is your favorite thing about your hair?
ALEX HARRIS: How smooth it is.
KATE HARRIS: Where I can just comb it back and then go do whatever.
MOLLY BLOOM: I have really curly hair, which I used to not like at all when I was your age. But now I like that I don't have to do anything to it, and it can just do its own thing. And whether you love your hair or just want to shave it all off, we're going to show you today how complex and cool it really is.
ALEX AND KATE HARRIS: Keep listening.
MOLLY BLOOM: You're listening to Brains On from American Public Media. I'm Molly Bloom, and my co-hosts today are Kate and Alex from Plano, Texas.
KATE HARRIS: Hi.
ALEX HARRIS: Hello.
MOLLY BLOOM: And you two recently got a closer look at hair. You wrote into us and told us that you were looking at strands of hair under a microscope. What gave you the idea to check that out?
ALEX HARRIS: We just got a new microscope, so.
KATE HARRIS: We decided to peek at hair.
MOLLY BLOOM: And what did you see when you looked at the hair?
ALEX HARRIS: Well, my hair was-- it had like little black dots all over it.
KATE HARRIS: And mine only had one. And my mom's gray hair had a ginormous line through it.
MOLLY BLOOM: Interesting. And you guys both have brown hair, right? But it looked different under the microscope.
KATE HARRIS: Yeah.
ALEX HARRIS: Yes.
KATE HARRIS: Much different.
MOLLY BLOOM: And when you put the hair under the microscope, is there anything special you have to do to it first?
ALEX HARRIS: You have to adjust it, then do lighting.
KATE HARRIS: And then there's also slides that you have to put it in to make it stay.
MOLLY BLOOM: So you take the hair and put it on a slide. And then you put it under the microscope. And you can see what it looks like really close up.
ALEX HARRIS: It's really cool.
MOLLY BLOOM: That's awesome. Well a little later in the show, we're going to talk to a scientist who looks at hair under a very powerful microscope. But first, let's start with the basics. A little hair 101, if you will. Here's a question to get us growing-- I mean, going.
AYALANDIA: My name is Ayalanda. I'm eight years old. I live in Calgary, Alberta. My question is, what is hair made of, and why do humans have hair and not fur like animals do?
MOLLY BLOOM: We'll get to the second half of that question later. But first, what is hair anyway? Is it alive?
ALEX HARRIS: It grows, but it doesn't have nerves the way skin does. You can pinch it without pain.
KATE HARRIS: And it's pretty strong stuff. But how is it so bendy?
MOLLY BLOOM: We asked Dr. Shani Francis to help untangle these questions. She's a dermatologist and the director of the Hair Center of Excellence-- awesome title, by the way-- at NorthShore University Health System in Evanston, Illinois.
SHANI FRANCIS: Hair is basically protein, but it has a very complex structure in how the protein is arranged. It's very organized. So the best way to describe it is like a rope of string that has many smaller ropes that are twisted and braided together. If you take a piece of yarn, OK, and when you-- you know how the yarn comes, and then you can unravel it and you see little smaller pieces of string.
Think about that, but amplify that and maybe take two or three or four, 30 pieces of string. And then coil those together in a rope. And that's how the structure of each hair fiber is. So basically it's pieces of string that have been twisted together. And then those twists have been twisted together. And then those twists have been twisted together. So you have just a big large rope. Very cool, and a lot of protein.
ALEX HARRIS: So each strand of hair is a collection of smaller strands, making the structure strong when it's pulled. But flexible when you bend it.
KATE HARRIS: Just like a rope.
MOLLY BLOOM: Here's another question we've gotten a lot.
ATTICUS: I'm Atticus, and I'm seven.
ELEANOR: Name is Eleanor.
ATTICUS: How does hair grow?
ELEANOR: How does hair grow?
KATE HARRIS: Hair growth starts with something called follicle. But wait, what's a follicle?
SHANI FRANCIS: Oh, hair follicles are everywhere. So everywhere you see a hair, you have a hair follicle. The hair itself comes out of this hair follicle, which is like a tube or a house tube that it lives in.
ALEX HARRIS: So follicles are basically tiny sacs in our skin where hair grows.
KATE HARRIS: They're lined with special cells that live in this follicle house.
[CHIRPING]
CELL 1: Ah, new day.
CELL 2: A glorious time to be a cell living in a hair follicle.
ALEX HARRIS: When they get a signal, they start their work.
[STEAM WHISTLE]
CELL 2: Oh, time to get cranking.
CELL 1: Yep. These hairs aren't going to grow themselves.
SHANI FRANCIS: And these cells rapidly divide.
[GRUNTS]
CELL 1: There we go. Two of me.
[GRUNTS]
[POPS]
CELL 2: Oh, hello, more of me.
SHANI FRANCIS: And as they are dividing, the old cells are getting pushed out of the way by the new cells.
CELL: It's getting crowded in there. Push those older me's out of here.
CELL: You got it. Move along other me's.
CELL: OK, OK, I'm leaving.
MOLLY BLOOM: As these older cells get pushed up the tube of the follicle, they leave behind all the blood vessels and nutrition keeping them alive.
ALEX HARRIS: They also get coated with special proteins known as keratin, making them tougher than living cells below.
SHANI FRANCIS: And so it's like an assembly line of hair cells moving up through this tubular house called a hair follicle. That's the reason why we think of hair fibers as dead, is because the part that's alive is the part that's dividing. And once it needs more space, it pushes the hair cells up. And that comes out as hair.
KATE HARRIS: Your hair growth has a few different cycles to it. First, there's the growth stage we just talked about.
ALEX HARRIS: It's called the anagen stage.
MOLLY BLOOM: During this phase, hair grows about half an inch a month, or six inches a year.
SHANI FRANCIS: The anagen part of the hair cycle lasts usually two to six years in most people. And most of our hairs are under this part of the hair cycle.
MOLLY BLOOM: After the anagen comes the catagen phase.
KATE HARRIS: During this period, hair growth stops. It lasts about 10 days.
ALEX HARRIS: Then the hair starts the final phase, known as the telogen stage. This one, the follicle takes a break from all its work.
[STEAM WHISTLE]
CELL 2: Phew, what a day. Feels like I've been working for at least six years straight.
CELL 1: Totally. I need a nap.
SHANI FRANCIS: And so in the resting phase, the hair is not growing. It's just sitting there. And at the end of the resting phase, which normally lasts two to three months, that hair is pushed out, and the cycle starts all over again. It's actually interesting, it's pushed out by new hair that's coming up.
[STEAM WHISTLE]
CELL 1: What a glorious day to be a cell living in a follicle.
CELL 2: Indeed. Time to get back to work. Hey, what's that old hair doing sitting there?
CELL 1: Oh, that was from the last shift, remember? Let's crank out a new hair to push it away.
CELL 2: You got it. Time to divide. Here we go again.
[GRUNTING]
[POPS]
KATE HARRIS: When old hires are pushed out by new hairs, you shed.
ALEX HARRIS: Don't worry, it's totally normal.
MOLLY BLOOM: In fact, most people lose anywhere from 50 to 150 hairs every day.
KATE HARRIS: But you've got thousands on your head, so it's hard to notice the difference.
MOLLY BLOOM: Before we start counting all those hairs on our head, we have another challenge for you. It's time for the mystery sound.
[MYSTERY SOUND CUE]
AUDIO TRACK: Mystery sound.
MOLLY BLOOM: Here it is.
[KNOCKING]
Any guesses?
ALEX HARRIS: I think it might be someone maybe tapping on glass or hammering.
KATE HARRIS: I think it's a hammer tapping on wood.
MOLLY BLOOM: Those are both really good guesses. We're going to be back with the answer a little bit later in the show.
AUDIO TRACK: Brains On!
MOLLY BLOOM: So far we've learned how hair grows, but now it's time to get into the why, as posed by Ayalanda earlier.
AYALANDA: Why do humans have hair and not fur like animals do?
MOLLY BLOOM: And Imogen.
IMOGEN: My name is Imogen Tree, and I'm six years old and from Newbury in the UK. My question is, why do we have hair?
KATE HARRIS: So to find out, we talk to Sandy Cook.
ALEX HARRIS: She studies the evolutionary biology of hair at Penn State University.
KATE HARRIS: Before she started selling hair, she did forensic analysis of hair for the FBI.
MOLLY BLOOM: For starters, Kate and Alex asked Sandy about the hair that they looked at under the microscope.
ALEX HARRIS: We saw by hair had a lot of black dots through it.
KATE HARRIS: And mine did not have. It only had one. And my mom had a black line through it.
SANDY COOK: If you think of a hair like structurally, it's going to be very similar to a pencil. So how a pencil has the paint covering the wood covering the lead, a hair has an outer cuticle layer, which is a very thin protective layer. And then there's the cortex of the hair. And that's where all the pigment granules are.
And then running through the center of the hair is called medulla. And that can be a dark black structure. And it can be completely present, like a line. It can be broken up and here and there. Or it could be absent. And it is a feature that we use when we do a microscopic comparison. So you were definitely seeing a lot of what we see when we look at hairs under a microscope.
With humans, we can tell general differences in ancestry. If a hair has been artificially treated, so if it's been dyed or bleached, we can tell. We can tell if there's been any damage to the hair. And there are differences that can be identified between people. But there's also variation within our own hairs so if you look at yourself in the mirror, you might see some slight variation in color, in length, and just some natural highlights.
And that's going to also appear microscopically. There's going to be some differences in the distribution of pigment. And there's going to be a range of characteristics.
ALEX HARRIS: Why do humans have hair, not fur?
SANDY COOK: Well, hair and fur are actually made of the same protein called keratin. And they're chemically the same. If you think about animals, we tend to think of our pets, dogs and cats, and they have fur all over their bodies. While humans, we have five million hair follicles on our bodies. But only about 100,000 to 150,000 of those are on the top of our head.
So we have hair all over our bodies. It's just in a much more reduced form. So if you look at your arms, you can really see very fine hairs. And that's our equivalent to fur. I think there are several theories about why humans may have reduced body hair, and that really relates to when our human ancestors started walking upright. One of the hypotheses are thoughts about why early humans may have not needed as much hair protection or fur coat on the whole body was that once they started walking on two feet, they really needed to be able to evaporate more of their body heat through sweating.
But there's still a definite need for protection from the Sun's rays on the top of a person's head so that we retained the head hair far more than we did our body hair.
MOLLY BLOOM: Well, thank you so much, Sandy, for being here today.
ALEX HARRIS: Thank you.
KATE HARRIS: Thank you.
SANDY COOK: You're welcome. And Kate and Alex, I hope you really enjoyed studying hairs and find out more. Bye-bye.
KATE HARRIS: Bye, Sandy.
[MUSIC PLAYING]
ALEX HARRIS: Do you have a question you want to hear on Brains On?
KATE HARRIS: Or a mystery sound share?
ALEX HARRIS: Or do you want to send us a high five?
MOLLY BLOOM: You can do that at brainson.org/contact. That's where we got this excellent question.
IAN: My name is Ian from Seoul, South Korea. My dad has been getting fuzz in his belly button. My question is, where is it coming from, and why don't I have fuzz in my belly button?
MOLLY BLOOM: We'll have an answer to that during our Moment of Um at the end of the show. And we'll read the most recent names to be added to the Brains Honor Roll. And hey--
[GROANS]
That sound means we made a mistake. In last week's Moment of Um, we said blood is blue when it doesn't have oxygen in it. But that's not true. Blood is always red. Red, red, red. It just looks blue in our veins because of the way light is reflected as it goes through our skin. So there you go. We made a mistake, but we corrected it. You can go listen to the updated answer in last week's episode, Why are Smartphones so Hard to Put Down?
[GROANS]
That made us feel sheepish. But we're all about talking feelings these days, because we're working on a series about emotions. And we want to hear from you, our listeners. We want to know what your body feels like when you're happy, or sad, or angry, or nervous. Pick one of those feelings and tell us how it makes your body feel. Send your answers to us at brainson.org/contact. Thanks, and keep listening.
[MUSIC PLAYING]
MOLLY BLOOM: You're listening to Brains On.
ALEX HARRIS: I'm Alex Harris.
KATE HARRIS: And I'm Kate Harris.
MOLLY BLOOM: And I'm Molly Bloom. Today, hair is on our heads and on our minds.
KATE HARRIS: And lots of people have written in with questions about hair.
ALEX HARRIS: So let's get right down to the answers.
WILSON: My name is Wilson, and my question is, why are some hairs different colors?
BEN: My name is Ben. What determines whether a hair is curly or straight?
MOLLY BLOOM: Excellent questions, as usual. Let's turn back to Dr. Shani Francis for the answers.
ALEX HARRIS: Starting with hair color.
SHANI FRANCIS: So pigment is what colors our hair. We have natural pigment in our hair. It's normally found in the middle of the hair follicle. So remember that shape of that rope of ropes? It's buried down in the middle. But sometimes in the darker hair, you can have it in the most outermost layer called the cuticle. The type of pigment in hair is called melanin.
And there are two different kinds of melanin. There's eumelanin, which is found in brown and black hair. And even skin. It's called eumelanin. And then there's pheomelanin, which is found in red hair and blonde hair. And this pigment is more yellowish-red.
MOLLY BLOOM: So your hair color is determined by how much eumelanin or pheomelanin you have in each strand.
ALEX HARRIS: People with dark black hair have more eumelanin.
KATE HARRIS: Light brown hair has less.
MOLLY BLOOM: Redheads have a lot of pheomelanin.
ALEX HARRIS: Blondes, not as much.
KATE HARRIS: What about gray hair?
SHANI FRANCIS: I like to explain it that the cells that are making the pigment are very closely related to that hair follicle. And so they throw in a little pigment on the hair follicle as it's rapidly dividing.
CELL: Adding pigment, always adding pigment. Making colors. I love adding pigment. Pigment, pigment, pigment--
SHANI FRANCIS: Those cells get tired, like all cells in our body as we age. And when they get tired, they burn out.
CELL: Adding pigment. Always adding pigment. You know what? I quit.
SHANI FRANCIS: And when they burn out, they stop producing pigment. And so if there's no pigment coming out of that cell, then there'll be no pigment in the hair follicle and there'll be no pigment in the hair.
ALEX HARRIS: OK, so that's color. But what about curls and waves and all the other textures of hair we have?
MOLLY BLOOM: Shani says it mostly comes from the shape of the follicle.
KATE HARRIS: You know, the house the hair lives in.
SHANI FRANCIS: And the shape of that hair follicle differs in different people. And so if that hair follicle or that tube that the hair is coming out of is more circular-- and really I mean like a perfect circle-- that hair will be straight. If that hair follicle house is oval, then you will see a curly hair coming from there. And the tightest, tightest curls, the kinkiest hair, is an extreme curly. And that shape of that house is more ellipsoidal. So like an exaggerated oval.
MOLLY BLOOM: Both your hair color and its texture are influenced by your genetics, or the genes you get from your parents. So you can thank them for whatever's growing on top of your head.
ALEX HARRIS: The hair on top of our heads has really been the focus so far. But that's not the only hair we have up there.
KATE HARRIS: We've got eyebrows, eyelashes, nose hair. All of it serves a purpose.
MOLLY BLOOM: We asked our friend Sanden Totten to break it all down for us.
SANDEN TOTTEN: The hair on and in our faces is super important stuff. I mean, it's there for a reason, right? Take Bob, for example.
BOB: Me again?
SANDEN TOTTEN: He's got hair above his eyes, around the lids, hair in his nose and in his ears.
BOB: I do. Huh, that's a lot of hair.
SANDEN TOTTEN: But what if we took some of it away? Like say we wax off his eyebrows.
BOB: Ow! That hurt.
SANDEN TOTTEN: And let's say we stuck Bob on a treadmill. You know, for science.
BOB: Oh man. Running? I shouldn't have eaten that sandwich right before this, huh?
SANDEN TOTTEN: Normally when we sweat or if it rains, that moisture will trickle down our foreheads toward our eyes. Eyebrows help divert those liquids to the side of the face. So it doesn't get in our eyes and we can still see. But without eyebrows--
BOB: Oh man. So-- so much sweat. My eyes. Oh, it stings. Ow.
SANDEN TOTTEN: And while Bob is busy trying to wipe the sweat from his eyes--
BOB: Ow! Anyone have an extra set of eyebrows I can borrow? Anyone? I hate exercise.
SANDEN TOTTEN: Next, let's imagine what would happen if we took away Bob's eyelashes.
BOB: I barely use those. I doubt I'll notice.
SANDEN TOTTEN: Eyelashes also help divert moisture. And when you squint, they shield your eyes from strong light, like the Sun. Like the brim of a baseball hat.
BOB: Now that you mention it, it is awfully bright all of a sudden. And my eyeballs are so dry and itchy. I can't stop rubbing them.
SANDEN TOTTEN: That's because lashes help block small particles, and even bugs from getting in your eyes. Scientists have also found that eyelashes help reduce wind flow across the eyeballs. That, too, keeps them clean from dust and prevents them from drying out too much.
BOB: My eyes feel like the Sahara Desert.
SANDEN TOTTEN: So that's two really important types of hair to help protect your eyes. But what about nose hair? It's not on your face, so it's not diverting sweat or shielding you from sunlight.
BOB: Yeah. Plus, it's just gross. Go ahead and get rid of it. Who needs it? Nose hair, I don't care. Nose hair--
SANDEN TOTTEN: But Bob should care.
BOB: Nose hair, I don't care-- hm?
SANDEN TOTTEN: Even though it's not glamorous, nasal hair is super important. Say we pluck out Bob's nose hair.
BOB: Plop?
[PINCHING]
Ow! Yow! Oh!
SANDEN TOTTEN: Now when he takes a big whiff of air--
[BIG INHALE]
--particles of dirt, pollen, and even germs have an easier time getting through his nose and into his body.
[COUGHS]
That's not good for his breathing or his health. Nose hair is like a built-in air filter. Ear hair does something similar.
BOB: Wait. I have hair in my ears, too?
SANDEN TOTTEN: Yes, Bob. We all do. But adults tend to have a lot more of it. It also helps filter dirt and dust. And without the hair in your ear, that fly buzzing around Bob's head might have an easier time getting stuck in his ear canal.
BOB: It's loud. Ow And it tickles.
[CHUCKLES]
This is a very strange sensation.
SANDEN TOTTEN: So clearly, the hair in and on our heads is useful stuff. So let's put Bob back the way he was.
BOB: Let's see. I have my eyebrows, thank goodness. And my eyelashes. So glad to see those. Ear hair, check. Nose hair? I think you gave me too much nose hair.
SANDEN TOTTEN: Sorry, Bob. That's the way we found you.
BOB: I should really trim these. It's like a forest in here. Why didn't anyone tell me?
SANDEN TOTTEN: So be thankful for the hair you've got. It's pretty neat stuff. And Bob, while you're at it, you might want to take a look at your ear hair, too. OK, back to you, Molly, Kate, and Alex.
KATE HARRIS: Thanks, Sanden!
[VOCALIZING]
AUDIO TRACK: Brains On.
MOLLY BLOOM: I know waiting has made your hair stand on end. So let's get back to the mystery sound. Let's hear it again.
[KNOCKING]
Any other guesses?
ALEX HARRIS: I still think-- maybe it's a hammer banging on a coffee table?
MOLLY BLOOM: So what do you guys think that might have to do with hair?
ALEX HARRIS: I'm not sure.
KATE HARRIS: Neither am I.
MOLLY BLOOM: Well, here with the answer is Shane Price.
SHANE PRICE: That was the sound of the hair board.
[LAUGHS]
We have no name for it right now, so that's the best thing that-- that's what we refer to it as here in the office. The hair board. The hair fiber board, something like that. Yeah.
KATE HARRIS: What's the hair board?
MOLLY BLOOM: What do you think it might be?
KATE HARRIS: Maybe a board that you keep hair on?
ALEX HARRIS: Maybe you study on it.
MOLLY BLOOM: Very good guess. Well, let's have Shane tell us what it is.
SHANE PRICE: It's a grayish brown. It actually looks a little bit like marble. It's got a marbled appearance to it. It's made up of hair fiber. But it's all compressed into a board. So when you look at it, it looks like some sort of tile or a board-like material.
MOLLY BLOOM: Shane runs a company called Green Circle Salons. He works with hair salons all over Canada and the US to recycle products that come out of those shops. There's lots of plastic and glass and aluminum foil, and there's also lots of hair. So how do you turn hair into a board?
SHANE PRICE: We work with an engineer in Montreal. He's created a metal frame. So it's in the shape of the board that we'd like. And he'll lie the hair down in this frame. And he adds resin to the hair and then uses a compression machine to force it down and to compress it. The hair fibers are all overlapping and mixed together, and the resin fills in the space where there's air.
And then during the compression, you're squeezing out all of the air so you just have hair and resin. And over time, that will harden into a sheet or a board of hair.
MOLLY BLOOM: Shane hopes that his hair boards will be used as furniture and shelving in some of the very same salons that sent him the hair to begin with.
KATE HARRIS: That is really, really cool.
MOLLY BLOOM: Yeah. And that actually is not the first time that they've used recycled hair. How else do you think they could reuse hair?
ALEX HARRIS: For wigs.
KATE HARRIS: Dolls.
MOLLY BLOOM: They actually use it in a very unexpected way. They take hair and stuff it into old nylon stockings to make something that's called a hair boom. And Shane helps manufacture these hair booms to help clean up oil spills.
SHANE PRICE: This was discovered back when the Exxon Valdez oil spill happened in Alaska.
NEWS ANCHOR: It's not only the worst oil spill in US history, it's by far the largest in such a remote pristine area. The tanker, the Exxon Valdez, had just loaded more than a million barrels of Alaskan crude. It was about 25 miles from the Valdez terminal and was apparently trying to dodge ice flows from the nearby Columbia Glacier when it ran aground.
SHANE PRICE: One gentleman that happened to be a hairstylist from Huntsville, Alabama, was watching the news and notice that the otters' hair was actually picking up the oil that was on the water. And so he had an idea. Well, he wondered if he was to take human hair from his salon, if it would do the same thing. And he quickly discovered that it would. And in fact, it's a great absorbent of oil.
KATE HARRIS: That is really cool.
ALEX HARRIS: I never knew that.
KATE HARRIS: Yeah. I never even knew about the Alaskan crash.
MOLLY BLOOM: Yeah, that happened in 1989. And Shane says that every 500 grams of hair, which is a little over a pound, that pound of hair can soak up about one liter of oil. And that's about a quart or the size of a large milk carton. And hair booms can be reused about a hundred times. Hair is both useful on our head and when it's not.
[MUSIC PLAYING]
KATE HARRIS: Hair is basically a rope of protein.
MOLLY BLOOM: The color comes from cells in your follicles. And the shape of those follicles make your hair curly or straight.
ALEX HARRIS: All of that is ultimately determined by your genes.
KATE HARRIS: There are thousands of hairs on your head that are constantly in the cycle of growing and falling out.
MOLLY BLOOM: And our hair isn't just there to look Pretty
ALEX HARRIS: Looks are a part of it. But they're also there to protect us and regulate our body temperature.
MOLLY BLOOM: That's it for this episode of Brains On.
KATE HARRIS: This episode was produced by Marc Sanchez, Sanden Totten, and Molly Bloom.
ALEX HARRIS: With production help from Cristina Martinez, Craig Johnson, Alan Roberts, and Jackie Sojico.
MOLLY BLOOM: Many thanks to Melissa and Ryan Harris, Eric Wringham, Meg Martin, Peter Cox, Lauren Plow, Nicole Rogers, and Daniela Kruschinski.
ALEX HARRIS: And you can keep up with us on Instagram and Twitter.
KATE HARRIS: We're at @brains_on.
ALEX HARRIS: And we're on Facebook, too.
MOLLY BLOOM: Now, before we go, it's time for our Moment of Um.
AUDIO TRACK: Uh. Uh. Um. Um. Um. Um.
IAN: Hi. My name is Ian from Seoul, South Korea. My dad has been getting fuzz in his belly button. My question is, where is it coming from, and why don't I have fuzz in my belly button? Thank you for answering my question.
[MUSIC PLAYING]
JARED JAGDEO: That is such a great question. I think that maybe kids are just much more well taken care of than parents are sometimes in terms of kids usually have a parent watching them. And maybe no one's watching the dad.
[LAUGHS]
My name is Dr. Jared Jagdeo, and I am a skin doctor. Belly button fuzz is made out of dead skin cells that slough off, lint or cotton or whatever other fabric from our clothing and our environment, and combined with sweat and other bodily secretions that really get in there. So a little bit of moisture, a little bit of skin, and a little bit of stuff from your clothing.
Dads' belly buttons may sometimes be a little bit deeper than the belly buttons that children have. Children have very shallow belly buttons, so not much builds up there. The deeper the belly button, the more likely the fuzz will be in there. Hair can play a role in the accumulation of belly button fuzz, and dads have also had a much longer time to allow for some natural fibers from clothing to build on up there in that area.
Everyone's belly button of fuzz is unique to them, because it comprises the different fibers from the clothing that we wear and also our own personal DNA, such as from skin cells and also from other things that maybe we're in contact with.
MOLLY BLOOM: This list makes my heart warm and fuzzy. It's time for the Brains Honor Roll. These are the delightful humans who keep us going by sending us their ideas, questions, and mystery sounds. We love them.
[LISTING HONOR ROLL]
AUDIO TRACK: Brains Honor Roll. High fives.
MOLLY BLOOM: We'll be back soon with more answers to your questions.
ALEX AND KATE: Thanks for listening.
Transcription services provided by 3Play Media.
