How do our eyes, skin and hair get their colors?

JEREMY: You're listening to Brains On, where we're serious about being curious.

ANNOUNCER: Brains On is supported, in part, by a grant from the National Science Foundation.

MOLLY BLOOM: Hey, Jeremy. Welcome to Brains On headquarters. I am so glad you're here for today's taping.

JEREMY: I'm so happy to be here.

MOLLY BLOOM: The studio is right this way.

JEREMY: Molly, what's that on your arm?

MOLLY BLOOM: Oh, that's from the Brains On freckle constellation contest we had earlier. See, I can connect these freckles on my arm into the shape of a dog. And that dog is doing the yoga pose, Downward Facing Dog.

JEREMY: Oh, wow. That is a really accurate description of that constellation.

RUBY GUTHRIE: Hey, Molly. Hey, Jeremy.

JEREMY: Hi, Ruby.

MOLLY BLOOM: Jeremy just got here for the taping.

RUBY GUTHRIE: Oh, man you just missed the [? consta-freckle ?] contest. I got first place.

JEREMY: I mean, I get why. You connected every freckle on your entire face.

RUBY GUTHRIE: And let me tell you, it took hours. I have a lot of freckles.

MOLLY BLOOM: It's so impressive. Who knew, all her freckles would make such a gorgeous succulent garden. Look, there's an aloe vera plant on her cheek, a saguaro cactus on her forehead, and a jade plant going across the bridge of her nose.

JEREMY: Oh. And I see a bonus constellation on your hand. Is it a banana swimming in a bowl of yogurt with a loaf of bread balanced on its head?

RUBY GUTHRIE: Oh, that? No, that's just my grocery list. I'm a visual thinker. What can I say? Oh, but I almost forgot eggs. Wait, can you pass me the pen?

[MUSIC PLAYING]

MOLLY BLOOM: You are listening to Brains On from APM Studios. I'm Molly Bloom. And my co-host today is Jeremy from Atlanta, Georgia. Hi, Jeremy.

JEREMY: Hi, Molly.

MOLLY BLOOM: Now, Jeremy, you wrote to us with a very excellent question. What was it?

JEREMY: I wanted to know why we have color in our eyes.

MOLLY BLOOM: It's a great, great question. So what color are your eyes?

JEREMY: My eyes are hazel, which is like a brown and green mix.

MOLLY BLOOM: Jeremy, how did you think of that question?

JEREMY: I was just really curious about-- I was really interested in my eye color because a lot of people say my eyes are a unique color.

MOLLY BLOOM: So what would you compare the color of your eyes to like? What is it similar to?

JEREMY: It's just like a darker green and yellow mix. It's a bunch of things.

MOLLY BLOOM: Yeah. So why do you think people think it's like an unusual color?

JEREMY: It's just not a lot of people have that eye color, or it's like, most people have just one color in their eyes, and I have multiple.

MOLLY BLOOM: So you've got green, and brown, and yellow?

JEREMY: Just a teensy bit of yellow. It's just a little bit lighter.

MOLLY BLOOM: Well, my eyes also have multiple colors. It's like greenish, bluish, almost gray, sometimes. What color is your hair?

JEREMY: I have brown hair.

MOLLY BLOOM: Me too. I also have brown hair. Since the people listening can't see it, how would you describe the shade of brown that your hair is, compared to something in the world?

JEREMY: I'd say, it's like a milky, chocolatey brown, really curly.

MOLLY BLOOM: Nice. I also have curly hair. And mine, I'd say, is probably the color of woodchips on the playground. And what color is your skin?

JEREMY: It's a light brown.

MOLLY BLOOM: Yeah, my skin, I would say, is like orangey, browny, peachy. If I had to compare it to something-- and I spent a lot of time thinking about this and asking my teammates what they thought. We settled on Graham cracker. Maybe a teeny bit lighter, but close to the color of a Graham cracker.

So what would you say your skin is the same color as?

JEREMY: Peanut butter or like a toasted marshmallow.

MOLLY BLOOM: OK. So we have delicious skin, turns out. Be a really good snack. So all these different colors in our eyes, hair, and skin are made by a super special substance called melanin.

JEREMY: Oh, yeah. I've heard of melanin. It's a pigment made by special cells in our bodies called melanocytes.

MOLLY BLOOM: Indeed. Cells are the building blocks of our bodies. And these are some very special ones. I think this is a great time to break out the old zoom ray and get a good look at the melanocytes in our skin. Care to do the honors, Jeremy?

JEREMY: Yes, please.

CREW: Zoom, zoom, zoom.

JEREMY: There it is, a melanocyte.

WOMAN: There I am, a melanocyte.

JEREMY: Did that melanocyte just talk?

WOMAN: The zoom ray really knows how to capture my good side, does it not?

MOLLY BLOOM: You are gorgeous.

WOMAN: I know. I am an artist, after all. I go by many names, Pablo Skimkasso, Kehinde Isley, Amy Harold.

JEREMY: I see what you're doing there. Amy Sherald is one of my favorite painters.

WOMAN: Amy Sherald may have painted an iconic portrait of Michelle Obama. But I make the pigment that gives you all your gorgeous color. All that melanin, I did it. I mean, Jeremy, look at your eyes. Could they be a more vibrant hazel? I think not. You're welcome. All the beautiful shades and colors found in human skin, eyes, and hair are made from just a few different pigments.

MOLLY BLOOM: There are different shades of melanin?

WOMAN: Yes, Molly. [LAUGHS] Who do you think I am, Eve Klein? Eve Klein, painted in one shade of blue. Anyway, yes, melanocytes can make different kinds of melanin.

JEREMY: What colors are these different types of melanin?

WOMAN: Thank you for asking. There is eumelanin, which is black or brown. And then pheomelanin, which is red and yellow. Watch this. I take some brown eumelanin and some pheomelanin, and I get--

JEREMY: Ooh, red hair.

WOMAN: Or maybe, I just take a smidge of brown melanin.

JEREMY: Blonde hair.

WOMAN: Or maybe I take brown and black melanin.

JEREMY: Brown hair.

WOMAN: I can do the same color mixing with skin and eyes.

MOLLY BLOOM: Very impressive.

WOMAN: So when we, melanocytes, make these pigments, these melanins, they're then stored and transported by melanosomes. Think of the melanosomes as my paint brushes.

MOLLY BLOOM: OK. You're a melanocyte. You make melanin, it's like paint. And the melanosomes are like paint brushes.

WOMAN: Excellent active listening, Molly. I've been consulting lately with a brilliant skin doctor named Jenna Lester. As an artist, it's important to me to really explore my process. And Jenna says these melanosomes are key.

JENNA LESTER: People with darker skin tones have larger melanosomes and more numerous melanosomes.

MOLLY BLOOM: Super interesting. So what about when we get a tan. What's happening there?

WOMAN: I'm so glad you asked. Well, I believe that art doesn't have to explain itself. My pigments do have a very practical use. Melanin protects your skin from the sun. The sun, we love her, but she sends out ultraviolet light, which can damage your cells. But not melanin. Melanin absorbs this UV light, protecting the cells that could be damaged by it. And when your body senses that it's being hit by this UV light, it will make even more melanin to protect you.

MOLLY BLOOM: The pigment acts like an umbrella. And when you're getting a tan, it's like tons of umbrellas opening up all around your skin to protect the skin cells underneath.

WOMAN: Elegant, simple, breathtaking.

MOLLY BLOOM: But sunscreen is still important. If you naturally don't have as much melanin in your skin, you'll burn first because it takes a little while for your melanocytes to make more melanin.

WOMAN: Art takes as long as it takes. Do not rush us. Respect the process.

JEREMY: What about freckles? Do you make those too?

WOMAN: Of course. Who could draw such beautiful, delicate dots but an artist? Here, my dermatologist friend, Jenna, explained this so beautifully.

JENNA LESTER: Freckles and moles happen because there is a concentration of melanin in a certain area. So for a freckle, it would be like in a small circular spot, wherever it's appearing on someone's body. And it concentrates in those locations more than in the surrounding skin.

WOMAN: The freckle process is started by sun exposure. And the melanin gets so excited about protecting you that sometimes, it sticks around.

JEREMY: Well, thanks.

WOMAN: You are so welcome. This has been a true pleasure. Now if you wouldn't mind zooming out again, Jenna is going to offer a critique of my most recent work. I call it Mole Elyssa.

MOLLY BLOOM: Oh, sure thing. Bye. Thanks, Jenna.

JENNA LESTER: Bye, Molly.

CREW: Zoom. Zoom. Zoom.

MOLLY BLOOM: That was so cool.

JEREMY: I feel like a walking work of art now.

MOLLY BLOOM: Me too.

JEREMY: I still have some questions, though. I get that melanin is there to protect our skin from the sun, and that tans and freckles come from the sun exposure. But why are we born with different shades of skin color, and hair color, and eye color?

MOLLY BLOOM: That is a great question. And we have someone here who can help us answer it. Tina Lasisi is a biological anthropologist at the University of Michigan. That means she knows all about human biology and evolution. And she actually studies this exact thing.

JEREMY: Hi, Dr. Lasisi.

TINA LASISI: Hi, Jeremy. How are you doing?

JEREMY: I'm doing good. What about you?

TINA LASISI: I'm doing pretty all right.

MOLLY BLOOM: Excellent.

JEREMY: What does your skin color tell us about our ancestors?

TINA LASISI: Our skin color tells us something about the solar radiation in the environment that our ancestors evolved. So let's say that you had ancestors that were in a place that was very sunny, near the equator. They would have dealt with a lot of solar radiation. And one way of protecting yourself against solar radiation is to have more melanin in your skin.

However, if you had ancestors that come from a place where there wasn't a lot of solar radiation, you get into trouble. If you have a lot of melanin because it does such a great job at blocking UV radiation that you don't get enough to make vitamin D, which is something that we need.

And of course, it's possible to have ancestors that come from multiple different places with all kinds of levels of solar radiation, in which case, your skin color might be somewhere in between all of those different skin colors.

JEREMY: Why did people in different parts of the world develop different hair and skin colors?

TINA LASISI: So when you think about humans, it's easy to think of us as groups of people who exist in different places in the world. But our history is a little bit more complicated. We all evolved initially from a population that lived somewhere in Eastern Africa, probably, maybe somewhere between Eastern and Southern Africa. And at that point, we all were in the same environment. And so we probably evolved to have very similar hair, very similar skin color.

But after that point, groups of people started going to different places. They started going to different parts of Africa. They started leaving Africa, going to the Middle East, going to Europe, going to East Asia, even going as far as the Pacific Islands and the Americas. And throughout all of those journeys, if people stayed in different locations long enough, they may have adapted to their environments. And what that looks like in terms of skin color is maybe having lighter skin color if there isn't a lot of solar radiation, or maybe having darker skin color if there is a lot of solar radiation.

The story with hair is a little more complicated. It seems that we might have evolved curlier hair really early on in human evolution. And then after that, it's not really clear if people adapted to environments with their hair, or whether it was just a question of a genetic lottery and just losing some of that variation along the way.

JEREMY: See, my mom is a lighter skin color, and my dad is a darker one, and I'm them mixed. So why is that?

TINA LASISI: Well, we have that in common, because my mom is very light skinned. She is from a country called Bulgaria, which is in Eastern Europe and pretty far up North. And it snows a lot there. And my dad is from Nigeria, which is bang smack on the equator. And it is very sunny there. And he has very dark skin. And I came out somewhere in the middle.

So what happens with people like you and me, if they have two parents who came from very different places, what happens is that you and I have one set of chromosomes that are passed from one parent. And they have all of the versions of genes that make traits like skin color that come from that population. And then they have another set of chromosomes that have all the versions of genes that make skin color from another population.

And because skin color is something that we call a complex trait, you end up having a blend of the two traits. So let's say you have a version of skin color gene 1. And you can have the light version, which we're going to call 0, or the dark version, which we're going to call 1.

Then if you have two copies of the dark version, you have two points. If you have one copy of the dark version, you have one point. And if you have zero copies of the dark version, you have zero points.

And so you can imagine, if you go through all the skin color genes and you tally up how many points you have, you can get this score of how light or dark your skin is, but there's a whole distribution of how light or dark your skin could be.

JEREMY: Thank you, Tina, for coming here.

TINA LASISI: You're totally welcome. It was my pleasure.

CREW: Baba, baba, baba, baba, baba, Brains On.

MOLLY BLOOM: OK, Jeremy. I am ready for a tiny break. Are you ready for the mystery sound?

JEREMY: I am.

[MUSIC PLAYING]

CREW: (WHISPERING) Mystery sound.

MOLLY BLOOM: All right. Here it is.

[CHISELING SOUND]

All right. What do you think?

JEREMY: It sounds like a chipping sound.

MOLLY BLOOM: What do you think is being chipped?

JEREMY: Sounds like a rock. But at the end of the sound, it sounded like a little bit metal. So maybe I'm going to say, something metal clashing with a rock.

MOLLY BLOOM: Very, very good guess. We'll be back with another chance to guess and hear the answer in just a bit.

[MUSIC PLAYING]

We are working on an episode about prehistoric creatures. We're talking dinosaurs, giant sea scorpions, megalodon, sabertooth tigers, mammoths, so many cool prehistoric creatures out there. So we want to hear from you.

We're asking you to write a haiku dedicated to your favorite prehistoric creature. As a reminder, haikus are poems that have a special format. They have five syllables in the first line, seven syllables in the second, and five syllables in the third. A syllable is one beat or sound in a word. The word "Name" has one syllable. And the word "Giant" has two syllables.

Here's an example. Giant dragonflies, that was five syllables, came before the dinosaurs, seven syllables. Name meganeura. So Jeremy, do you have a haiku for your favorite prehistoric animal?

JEREMY: Yes, I do.

MOLLY BLOOM: Let's hear it.

JEREMY: Giant teeth, long tail, each 10,000 fish, one gulp. Whoa. Megalodon.

MOLLY BLOOM: Oh, yeah, Jeremy, that was so good.

JEREMY: Thank you.

MOLLY BLOOM: Well, listeners, please send us your prehistoric haikus at brainson.org/contact. And while you're there, you can send us mystery sounds, drawings, and questions.

JEREMY: Like this one.

ALEXIS: I'm Alexis. And I'm from Minnesota. And my question is, how do fireflies glow?

MOLLY BLOOM: Again, that's brainson.org/contact.

JEREMY: And keep listening.

You're listening to Brains On. And I'm Jeremy.

MOLLY BLOOM: And I'm Molly.

JEREMY: We've been talking about melanin, the super cool pigment that gives our eyes, hair, and skin its color.

MOLLY BLOOM: But guess what. Melanin isn't just in humans. This stuff is found in all sorts of animals, plants, and even fungi. Fungi are living creatures that include mushrooms, molds, and mildew. So that brings us back to our mystery sound.

Before we listen again, Jeremy, I just want to let you know that this is not a sound from one of our listeners. This comes from a scientist. And it's related to melanin.

JEREMY: OK.

MOLLY BLOOM: Here it is again.

[CHISELING SOUND]

New thoughts, Jeremy? Last time, you thought a rock and something metal.

JEREMY: You said it was related to melanin. So it's completely out.

MOLLY BLOOM: Or is it? Or is it?

JEREMY: I really-- no, it's so-- that sound is just really confusing. I don't even know. I think I'm going to stick with my first answer.

MOLLY BLOOM: OK. Excellent work, Jeremy. Here is the answer.

MENAKA WILHELM: The sound you just heard was a researcher using a chisel and a hammer to break open a rock. And she was looking for something living inside of that rock. And guess where the rock was. It was in Antarctica.

MOLLY BLOOM: You were right.

JEREMY: Wow.

MOLLY BLOOM: Nice work.

JEREMY: Wow.

MOLLY BLOOM: 100%--

JEREMY: Thank you.

MOLLY BLOOM: --correct. So good.

JEREMY: Wow. So yeah, it was confusing because it was like, how could a rock and a chisel be connected to melanin? But it's because that researcher is looking for fungi inside of the rock that actually have a lot of melanin.

So long time listeners of Brains On might be thinking that that voice you just heard sounds familiar.

MENAKA WILHELM: My name is Menaka Wilhelm. And I write and talk about science. I used to do it at Brains On. And now I do it with scientists at a research lab called the Joint Genome Institute that's part of a bigger lab.

MOLLY BLOOM: That's right. In addition to being our favorite sheep shearing student, Menaka also helps explain cool science, like the story behind that sound you just heard.

MENAKA WILHELM: The recording is actually from Antarctica. It's from a real life scientists work. And her name is Laura Selbmann. She studies tiny microscopic fungi. And she's based in Italy, at the University of Tuscia.

MOLLY BLOOM: OK. So fungi is a group of living things that includes mushrooms, and mold, and yeast. But what does this have to do with melanin?

MENAKA WILHELM: So fungi can have melanin too. It's a little bit different from the melanin that we have, the kind in our skin. But it's still super interesting. And that's why Laura studies it. She looks around all over different places in the world for teeny, tiny fungi with tons of melanin. This kind of fungi are called black fungi. And they're actually different from black mold, although it's confusing. That's technically a black fungus also.

But one place black fungi live is inside of these rocks in Antarctica. These fungi can just live on very, very little. They can live with very little water, with very little nutrients. It's pretty wild. They can just keep their life going.

MOLLY BLOOM: Wow. For me, I need a comfy room that's not too hot or too cold, plenty of snacks, and a whole lot of water and coffee to just get through the day. But life forms like this. They can live in extreme places where other life can't survive. That's why they're called extremophiles.

MENAKA WILHELM: And so fungi like this can also live in other extreme places in the world. So not just cold places like Antarctica, but also super hot places like Joshua Tree National Park in California. They can even live in places with lots of pollution, like this river called the Rio Tinto in Spain. And sometimes, these fungi live outside, like on marble monuments. If you think of a statue that looks white, but you see black cracks, that can be black fungi. And when they live there, they eat air pollution to survive.

It definitely seems like the melanin is helpful. For sure, their melanin can protect them from some dangerous chemicals. But we don't totally know yet. There are still more melanin mysteries to solve. So Laura and lots of other researchers are still out there working on it.

MOLLY BLOOM: If you miss Menaka, she makes a podcast called Genome Insider, where they talk all about cool research happening at her lab.

CREW: Brains On, on, on.

JEREMY: So melanin is everywhere. But it's a little mysterious, and it's a little magical.

MOLLY BLOOM: Definitely. Melanin is found all throughout the tree of life, in plants, insects, fungi, birds, you name it. Since it is so common, you'd think we'd know all about it, but nope. Turns out, there are lots of melanin mysteries still to be solved.

Let's check back in with our melanocyte pal to find out more.

WOMAN: Oh, hello. It's me that genius melanocyte artist you were swooning over earlier in the episode. Welcome to my art show. All my finest pieces are on display in this gallery, here in the world renowned MoMA Museum. Every piece is painted with, you guessed it, melanin.

Melanin is my paint, my medium, my muse. It's a fascinating and beguiling substance.

MAN: Wait, excuse me. Are you the artist behind all this work?

WOMAN: Yes.

MAN: I'm a very serious and real art collector. You can tell because I have a tiny thin mustache and a large fancy silk scarf.

WOMAN: Oh, true. Proceed.

MAN: Well, I'm a tremendous fan of your work. And I'm interested in purchasing a piece for my collection of art stuff that I have because I am, in fact, a very real art collector, for real. Definitely not a scientist curious about the workings of melanin.

WOMAN: Of course. Nothing suspicious about that. Obviously, you would want one of my paintings.

MAN: Obviously. Tell me about this one here.

WOMAN: Oh, yes. Yes. The one that looks like a bolt of lightning, it's titled, What A Shock. You see how it glows? Well, that's because melanin actually has the power to conduct electricity. It's similar to how wires can send electricity from one place to another. Melanin can do that too.

MAN: Fascinating. I'd love to know more about this, and also, how melanin is made. For instance, in excruciating detail, perhaps, with charts and graphs.

WOMAN: Odd request, but I get it. Scientists around the world are curious about the same thing. Scientists understand how lots of other parts of the human body are made, like DNA, for instance, or proteins, amino acids. Those are pieced together like LEGO blocks, building a larger structure, simple and boring. But I make melanin in a more spectacular and mysterious fashion. Instead of a factory, it's more like the flash and bang of a fire, as you can see in this painting, which I call Combustion.

[EXPLOSION]

MAN: Yes. And exactly how does that happen? Please talk into my pen here, which is not a microphone. It just looks exactly like one.

WOMAN: Oh, I would never tell. I need to keep the air of mystery around my work. You understand, right? Anyway, just like a fire starts quickly, melanin is also made quickly, so quick that it's hard for human scientists to figure out how exactly it's made.

MAN: Infuriating. I mean, fascinating.

WOMAN: Yes. Human scientists really, really want to know and have been trying to figure it out for over 100 years. I am an artist, however, and am loath to reveal my secrets. It would be like Clark Kent just coming right out and telling everyone he's Superman, or KFC giving away the special blend of herbs and spices.

MAN: Or me telling you, I'm actually a scientist in disguise.

WOMAN: Exactly. Where's the magic in that? Wait, what did you say?

MAN: Absolutely nothing. Unrelated question that is, in no way, a distraction from what I just accidentally said, why is this painting shaped like a brain?

WOMAN: Oh, this one, I call Gray Matter. It represents the pain and struggle human scientists face when trying to figure out why melanin is in the brain. I mean, melanin helps protect skin from the sun. But the brain doesn't need sun protection. Why is it there? Those scientists can't figure it out, drives them bananas. Bananas, I say. [LAUGHS]

MAN: Yes, ha, ha. Those scientists, sure, are curious. But we know the real reason, right?

WOMAN: Yes, but I won't tell. Maybe I will. No, I won't. No. OK, no, no, no, I'm not going to do it. [LAUGHS]

MAN: Why not, though? I mean, hypothetically, if, say, you told a scientist your many secrets, they could, I don't know, make amazing sunscreen from melanin or harness its ability to conduct electricity, to make better solar panels, or even make amazing new medical devices. We-- I mean, they could do so much good if they could crack the mysteries of melanin.

WOMAN: True. True. But that's for them to discover through copious amounts of research. If I just told them, that would be cheating.

MAN: No, it wouldn't. You could just tell me. I promise, I won't tell. I don't even know any scientists, especially not all of my friends. They are definitely not scientists. And we don't have science parties and play science games every Tuesday after work.

WOMAN: Of course, you don't. You are a big time art collector interested in my-- wait a minute. Is that a lab coat under your fancy silk scarf? And that's not a thin mustache. It's just a line drawn with a marker. You're an imposter. A scientist.

MAN: Drats, the jig is up. Gotta go.

[FOOTSTEPS]

WOMAN: Oh, I should have known. Anywho, if you'll excuse me, I have a performance piece to get ready for. It's called, The Artist is Present. It's where I sit and stare at scientists. As they try to unlock the secrets of melanin, I say nothing. It drives them batty. So fun.

Anyway, thanks for dropping by. There are cheese cubes and bubbly waters by the door. Mm-hmm. Mm-hmm.

[MUSIC PLAYING]

JEREMY: Our eyes, skin, and hair all get their color from melanin.

MOLLY BLOOM: Melanin is made by special cells in our body called melanocytes.

JEREMY: Melanin can be found in all sorts of living creatures, from plants, to insects, to birds, to fungi.

MOLLY BLOOM: The skin color you're born with tells a story about where your ancestors live long, long ago. That's it for this episode of Brains On.

JEREMY: This episode was written by Molly Bloom, and produced by Rachel Brees, Rosie DuPont, Anna Goldfield, Nico Gonzalez Wisler, Ruby Guthrie, Marc Sanchez, Anna Weggel, and Aron Woldeslassie.

MOLLY BLOOM: Our editors are Shahla Farzan and Sanden Totten. And our executive producer is Beth Perlman. This episode was sound designed by Rachel Brees and engineered by Alex Simpson and Sawyer Vanderwerff. Many thanks to Julie McGuire, Micah Middleton, Matt Alvarez, Joy Dolo, and Bern Kohler.

The executives in charge of APM Studio are Chandra Covatti, Joanne Griffith, and Alex Schaffert.

JEREMY: Brains On is a non-profit public radio program.

MOLLY BLOOM: There are lots of ways to support the show. Head to brainson.org. While you're there, you can subscribe to our Smarty Pass, where you can listen to ad-free episodes and super special bonus content.

[MUSIC PLAYING]

Now it's time for the Brains Honor Roll. These are the kids who keep the show going with their questions, ideas, mystery sounds, drawings, and high fives.

[MUSIC PLAYING]

[LISTING HONOR ROLL]

[MUSIC PLAYING]

CREW: Brains On Live.

MOLLY BLOOM: We'll be back next week with more answers to your questions.

JEREMY: Thanks for listening.