Radiolab - Growth

Episode Date: March 14, 2025

It’s easy to take growth for granted, for it to seem expected, inevitable even. Every person starts out as a baby and grows up. Plants grow from seeds into food. The economy grows. That stack of mail on your table grows. But why does anything grow the way that it does? In this hour, we go from the Alaska State Fair, to a kitchen in Brooklyn, to the deep sea, to ancient India, to South Korea, and lots of places in between, to investigate this question, and uncover the many forces that drive growth, sometimes wondrous, sometimes terrifying, and sometimes surprisingly, unnervingly fragile.Special thanks to Elie Tanaka, Keith Devlin, Deven Patel, Chris Gole, James Raymo and Jessica SavageEPISODE CREDITS: Reported by - Matt Kielty, Becca Bressler, Pat Walters, Sindhu Gnanasambandun, Annie McEwen, Simon Adlerwith help from - Rae MondoProduced by - Matt Kielty, Becca Bressler, Pat Walters, Sindhu Gnanasambandun, Annie McEwen, Simon AdlerSound design contributed by - Jeremy Bloomwith mixing help from - Jeremy BloomFact-checking by - Emily Krieger and Natalie Middletonand Edited by  - Pat WaltersEPISODE CITATIONS:Audio:“The Joy of Why,” (https://www.quantamagazine.org/tag/the-joy-of-why/) Steve Strogatz’s podcast. Articles:“The End of Children,”(https://zpr.io/WBdg6bi8xwnr) The New Yorker, by Gideon Lewis-KrausBooks:Finding Fibonacci (https://zpr.io/3EjviAttUFke) by Keith DevlinDo Plants Know Math (https://zpr.io/bfbTZDJ8ehx5) by Chris GoleSingup for our newsletter!! It includes short essays, recommendations, and details about other ways to interact with the show. Sign up (https://radiolab.org/newsletter)!Radiolab is supported by listeners like you. Support Radiolab by becoming a member of The Lab (https://members.radiolab.org/) today.Follow our show on Instagram, Twitter and Facebook @radiolab, and share your thoughts with us by emailing [e-mail] support for Radiolab’s science programming is provided by the Gordon and Betty Moore Foundation, Science Sandbox, a Simons Foundation Initiative, and the John Templeton Foundation. Foundational support for Radiolab was provided by the Alfred P. Sloan Foundation.

Listener supported, WNYC Studios. Oh, wait, you're listening? Okay. All right. Okay. All right. You are listening to Radiolab. Radiolab.

From? WNYC. See? Yep. Okay, so we're going begin with producer Matt Kilty. Okay, Latif, let me take you to the land of the Midnight Sun. Whoa, is that Japan? No.

No, Rising Sun is Japan. Oh, the Midnight Sun's probably gotta be Antarctica or something. Alaska. Alaska. Oh, do you see the mountains all the way out there? Those are snowy. That's beautiful. Specifically. Jagan Mountains kind of everywhere. Palmer, Alaska, which is like an hour north of Anchorage. Never heard of it.

Yeah, it's a little town where they host, every summer, the Alaska State Fair. Got a wallet. I have a phone. Okay. Which is where I went last August with. You know, I've never seen a corn dog that I don't like. My childhood best friend, Mike Gladney. So I'm pretty excited.

And Mike and I were from Minnesota, which has a really big state fair, Alaska's. It's like a small county fair. It's a little bit smaller, but does have a lot of good food. Oh, right there! A lot of classics, but also... Alaska crab cakes!

A lot of great seafood. Salmon quesadilla. And then of course games, rides. But! Latif? Yeah? This little fair does have something very, very, very big.

Woo! something very, very, very big. Which is the annual Great Pumpkin Way Off. Ooh, so this is like a state fair competition. That's right, a competition to see who can grow the biggest, heaviest pumpkin in the state, but also maybe in the world. Okay. Because in Alaska... We grow the best pumpkins in Alaska. We grow the biggest pumpkins around.

I know, Why is that? I think they put milk in them. They just water them with milk the whole time. That's what I heard. Mike and I talked to one of the workers, Kathy Liska. This is my 31st year working in the crops department, and I've seen maybe, I think, about 25 Guinness World Records. Wait, pumpkins specifically?

No, no, no. All sorts of stuff. Carrots, beets, cabbages. What's Alaska, you know, what's the fair known for? It's the giant vegetables. Because in Alaska, in the land of the midnight sun, plants can get a ton of sunlight, and so essentially you can grow these plants to like really, really big sizes. There's a lot of growers all around the world that'll be keeping their eye out around here to see what's going on. So.

Okay, wait, we should describe what we got. We got Mike, Kathy, me. You call it a barn farm? It's an open-air arena, yeah. This is our ag building. We're standing in the ag building. Smells like not good in here. And we are standing inside this like cattle pen, this little fenced-in area.

We are surrounded by bleachers. So here we are, center ring. When out comes Where's the, oh my god. Oh here we are, center ring. When out comes this huge... Wow. It's enormous. It's gigantic. Orange pumpkin. It's intimidating looking.

Kathy, is it okay if I touch the pumpkin? And this pumpkin. Can you feel the magic? You're touching it too. It's about the size of a Volkswagen Beetle. Wow. It's got like a heartbeat. It does actually weight. It's alive. It's just the size of a Volkswagen Beetle. Wow. It's got like a heartbeat. It does actually weight.

It's alive. It's just so big. Except it's like lumpy and like kind of blobby. Like Jabba the Hutt kind of? Yeah. Could you and Mike have fit in the pumpkin? We could have crawled inside the pumpkin and held each other. Weird.

That's 98 days old right there, that pumpkin. So the pumpkin belongs to this guy, Dale Marshall of Anchorage. I'm sick of that thing, tell you the truth. He's a season grower. Are you pleased with your pumpkin this year? Oh yeah, just getting one here is half the battle, you know? When I see something this big, I'm like, this is frightening. I like it, I like the color.

You know how long it took me to paint all those little spots on there? And while we're talking, Oh, oh, they're putting a thing. Dale rushes over to his pumpkin. Something's happening. Here we go. Here we go. And basically, Michael, get over here, thing. Dale rushes over to his pumpkin. Something's happening. Here we go. Here we go.

And basically, Michael, get over here, Mike. Mike and I get in position, and then we watch them as they push this pumpkin so it's underneath this crane. Everybody looks like they're excited, they're anticipating. And dangling from the crane,

bated breath, are these straps. Everyone's circling. Okay, Dale's getting the straps ready. Dale takes the straps from the crane, wraps them down around the pumpkin. Pumpkin appears to be strapped in there, securing the rope.

Ties it all together with a rope. This is nerve-racking. And then... You could hear a pin drop in there. The crane begins... The straps are tightening. To lift the pumpkin. Here we go, it's up off the pallet.

It's off the pallet. Up into the air, so it's dangling like two feet off the ground. And then... Jodi, careful, Jodi. Come on, your side, Jodi. A volunteer named Jodi gets on her back, climbs underneath this pumpkin.

So it's just dangling above her and she inspects the pumpkin for like any holes, any tampering. All right. She gives a thumbs up. Jodi's a wild woman. And then, okay, all right, they're transporting it over to the scale.

The crane begins to lower the pumpkin under this huge metal scale Okay, all right, they're taking straps off and and the rope all it's coming off Okay, fully on the scale Dale steps back from his pumpkin. It's on the scale. It's being weighed. Okay, and then The moment of truth. Oh My god, oh my are. Oh my god, 2000 pounds. Oh my god. Oh my god. First place, grand prize winning 2035 pound pumpkin. Oh my god. Oh my god.

To put that into perspective, that is about 8 to 10 panda bears. Just to give you a sense of the weight. All right. A lot of pandas. Anyway. High fives all around for Dale. Dale's psych. Dale's got his arms in the air. He's running around his pumpkin. How are you feeling? Well, I'm ecstatic. That's about 150 pounds more than I thought I was gonna get. And then pretty quickly. We're moving it. We're moving it. We're moving it. I'm out of here. I'm out of here. The local news crew surrounded Dale. He gets a ribbon, a thousand dollars. And then that's pretty much it.

Okay. Yeah, it's kind of everything. And was this a record static pumpkin then? No. Actually, it didn't even beat Dale's previous pumpkin record in the state. But it was a good pumpkin, first place pumpkin. But then what happens to the pumpkin afterwards a good, it was a good pumpkin. First place pumpkin. But then like what happens to the pumpkin afterwards?

Well, Dale typically takes his home. He says his grandkids like to play on it. And, or if you don't do that, you can donate it to the Alaska zoo or the wildlife conservation center where they will feed it to bears. Bears? Yeah. Grizzly bears. I feel like an Alaska punchline joke that you would make up.

Right? No, it can't feed bears. Itly bears. That feels like an Alaska punchline joke that you would make up. Right? No, it can't feed bears. It is bears. Because it's not fit for human consumption? Or is like, could you eat these? Yeah, yeah, you can eat them. I don't think they taste very good. They're not being grown for flavor.

It's just so hard to imagine the point of this. What do you mean? Like, what are we... what... What are we doing? What are we doing here? Well, I mean, for the growers, I think it's just like, it's like pushing the limits, like, just you're trying to grow something really... Stronger, faster, bigger, better, dah, dah, dah, dah, dah.

Yeah, exactly. But I think, for us, to be there, like, if you average it out, Dale's pumpkin grew 20 pounds a day. And to just come and look upon that. I think it's cray cray. To see something that's just so incomprehensibly big. I think it's crazy how big it is. It just stirs up. Look how big that thing is.

This real sense. It's gorgeous. I think it's beautiful. Really? Of awe. I do, because it's so big. I mean, where else do you see something like that? Because seeing something like that just sort of makes you think about the fact that everything has this blueprint for growth, for how it's

supposed to grow, for what it's supposed to grow into. And yet here you are confronted by something that seemingly doesn't fit that blueprint at all. And that is what we're doing there, Latif. Coming together to feel a little bit of joy, a little bit of terror brought on by an enormous pumpkin. Okay. All right. Sure.

All right. This is Radiolab. I'm Lulun Miller. I'm Lutif Nasser. Today we are looking at growth, which is actually an episode we started working on when you were off growing a person. Yeah, actually, my belly was just like that pumpkin. It was like, bigger and bigger. To like touch my toes or tie my shoes. And then the baby came out and she has already doubled in just a few months. He's already doubled in size. But we have we have more. This is not an hour about pumpkins as much as I know you would have wanted that. We have three different stories about growth, growth that happens in places

you'd never expect, growth that follows a pattern that seems woven into the universe itself, and even a growth that has taken over the whole planet and, for better or worse, the surprising thing that might stop it. All right, let's do this thing. First up, we have a story from Becca Bressler. Hello. Hello. Hey. Okay, so I'm going to take you from pumpkins to carrots.

Okay. Huge leap, huge leap. Orange vegetable to orange vegetable. Stick with me. This story starts in a kitchen. Okay. So this was a few years ago, November 30th, 2021. With this woman named Raymondo.

All of my housemates were away for the evening, and I was making dinner. I have vegetables out, there's broccoli, there's carrots. Music is playing. Vibes are good. Pretty normal evening. And as I'm chopping, chop, chop, chop, chop, chop, chop, all of a sudden... She looks down and was like...

I just cut off my fingertip! The end of her left middle finger from halfway down the nail was just gone. The wound was just white for a moment. And then I saw just like the river of blood like rise. So she grabs paper towel, presses it up against her finger that's gushing blood. Oh. And she immediately calls her friend Amy. My best friend Amy.

Used to be a trauma nurse. Person to call. Right person to call. So Amy picks up. They tell Raida bandage it. Keep pressure on it. Go on the couch. Elevate it. And just like dissociate for a while. Wait, but she didn't go to the ER or something? So actually that was the question that consumed her. I'm like, how much is having a fingertip worth to me?

Like, can I put a dollar amount on it? Her deductible was super high. If the emergency room bill were going to be $5,000, nah, I'm good. Like, I can live life without a fingertip. If it's $1,000, I'm like tempted, but like, geez. Yeah. I do really like having like all my fingertips, like.

But eventually she decides it's not worth it. No. And at that point, I was like, I'm done. I have a short middle finger now. This is just my life. Yeah. But... over the next few days, as Ray gets into a routine of changing out the bloody bandage, she starts to notice a couple things happening.

Uh-huh. One, what I noticed was my fingernail She starts to notice a couple things happening. Uh-huh. One. What I noticed was my fingernail continued to grow outward in the same shape that it grew before. And two. The finger started to fill in underneath the fingernail that was growing outward. And after a few weeks. I was like, wait a minute, like...

Is my fingertip growing back? And slowly but surely, it was just sort of like, whoop. My finger was back. [♪ dramatic music playing over speakers and speakers' voices. [♪ dramatic music playing over speakers' voices. [♪ dramatic music playing over speakers' voices. What? [♪ dramatic music playing over speakersERS"] What? Like her whole fingertip grew back? Yeah. Like you couldn't even tell if anything happened to it? No.

Now it's like, I would say 99.5% back to normal. Man, this feels so... Like, I mean, I've heard of human... Like, you can regrow skin, I get that. Like, I feel like I vaguely heard of someone regrowing part of a liver back maybe? Yeah. But like, this is different. This is like, there's a whole, there's a bone in there. There's like, there's so much going on.

Yeah, it does feel more complicated. There's layers. It's a flesh lasagna that you're growing back home. Actually, totally. I had never heard of this before. And obviously this was very surprising to Ray. Oh, totally. And so actually she emailed us to tell us about this. To be like, what? I mean, how?

Like, am I a mutant with superpowers? Kind of, yeah. She wanted us to find out how did this happen? Like, how did my fingertip grow back? Right. So Ray and I together called up. It's nice to meet you, Ray. Oh, it's so nice to meet you too. This guy.

Can I see your finger? Oh yeah. So this is Ken Muniyoka. He actually studies fingertip regeneration. Currently at Texas A&M University. And Ken wasn't that surprised to hear about Ray's fingertip. I felt bad for you, but I suspected it all came back. He says that people have been writing about this

for nearly 100 years. Yeah, that story begins back in the 1930s. A physician in Canada had a severely infected finger and he basically removed the bone out of his finger. Just the tip of it. And he, he, but he x-rayed it, and he sort of followed it with time, and he found out that his whole finger regenerated.

Wow. Ken also told us that back in the 70s, doctors in the UK saw a bunch of kids with chopped off fingertips. There was a reasonable number of them coming into the clinic. No idea what was going on over there, but... They documented hundreds of children regenerating their fingertips.

So Ken studies this stuff at a microscopic level. In fact, I spend most of my time working with mice. Unfortunately, or fortunately, there aren't a lot of controlled studies around chopping off human fingertips and seeing how they grow back. But thanks to our good friends, the mice. We're able to follow the regeneration process using this machine called a micro CT. What's that? So it's like a CT scanner, but it's like for tiny little things. And Ken says that when you cut off your fingertip, a few things happen. You know, the initial response to a trauma like that is an inflammatory response that

cleans up the wound. Pretty standard stuff. But then, sometime after that... Something very unusual happens. Stem cells that are in the nail bed, that are normally required for having your nails grow continuously throughout your life. They sort of kick off this rebuilding process. Forming this sort of organizing response to make the other parts of the tissue in that

lost fingertip. So this is Chris Arnold. He's a professor at West Virginia University. In the biology department. And he says that these stem cells under the nail call up a bunch of other stem cells in the body. You know, cells that can make bones. Skin tissue. Nerves.

Muscle tissue. And so these different types of cells basically start regrowing what was lost. And eventually you have a whole brand new fingertip. Huh, like we plumped back out to what it was. Yeah. How does it know when to stop, right? Like if your fingertip grows back,

it doesn't become bigger than it was before. There's apparently, there are signals to stop regeneration, but we don't know exactly where it's happening, when it's happening. Got it. Weird. Also, can I just say, what a weird use of stem cells. It's like you have these miracle cells in your body that can do whatever, regrow whatever,

and then it's like, okay, you know what we need you for? Just keep regrowing nails that we're going to have to cut anyway. It seems like so futile, right? Yeah, so that's exactly what I said to Chris. Yeah, so it doesn't make a lot of sense for us, right? As like, why is it our nails just keep growing and growing? But if you think a little earlier for earlier mammalian ancestors,

maybe that's where you actually get more of the answer of why this is happening. Because I mean, from our earlier sort of kind of rodent-like ancestors, known for their ability to dig, burrow into new environments where you're getting this constant damage, and so that may came along with it, this ability to constantly regrow from that damaged kind of part. Wow. It's kind of crazy to just like look down at them and be like, I have these because of rodents? Exactly, yeah.

Like should I go use them and burrow? I don't know. Yeah. Are you burrowing with them? Like, what are you using your nails for? I know. Really? Ha ha!

I'm never going to look at my fingernails the same. It's like the former us hunched over trying to dig away. Yeah. But when Chris started telling me about other animals. There's animals that regenerate even better than that. I realized that word not that impressive at all. Yeah, so if I could regenerate like a salamander, if I cut off my hand, a new hand would grow back in its place.

And as he told me about more and more of these creatures, it just kept getting weirder. Like our friend the planaria. Mm-hmm. So there's this tiny little flatworm called a planaria. If you cut it into small pieces. Even hundreds of them. Those pieces can regenerate the entire animal over again. So the whole body can grow from any part.

Some starfish can also do this. You can cut off one of their arms and that can become a whole new starfish. There was a famous story where scuba divers were trying to get rid of a starfish population in their area by going down and cutting them into little pieces only to find to their dismay that the next day, well, the next few weeks, they're even more starfish than they started with.

Okay, now this is my favorite thing. So, you know the classic one, lizards, right? How they can break off their tails and grow them back. What's amazing though is that they have this tear away site on their tail. Kind of like, I think of like the perforated part of like a ketchup packet or something. It's like a coupon. Exactly. But they're not the only animal that has one of these.

The sea slug. Oh. But it's not the tail they're losing. They actually lose all of their body from the neck down. It turns out that when they're sick, they can just shed their entire body. And at the end, it's just a head that's swimming around that will then go on to regenerate all the rest. Oh my god.

Wow. I've been sick over the last few weeks and that is just so relatable. Like I have thought about doing that so many times. Now I'm coughing. It is wild that you can just dispense of a body and be ahead and then grow a new body. I mean, when it goes to that level, it does feel like a superpower. No, totally. I know these things feel like superpowers to us. Yeah. We generally think of animals more like a planaria,

something that could regenerate its whole body is just something weird and alien. But Chris told me that this thing that seems just like a strange little quark of nature is really not that strange at all. When we look at the tree of life, the ability of an organism to regenerate itself from a small piece, whole body regeneration, the most extreme form of regeneration. That is actually very widely distributed throughout the tree of life.

Wow. And it's only been lost in a couple of branches. Ours is one of them. And so it's not really weird that an animal can regenerate its whole body. It actually might be more weird that we can't. Why can't we do this though? Why are we the ones left out? Yeah. I mean, scientists think that it's because we're complex, right?

They typically see these regenerative properties in simpler organisms. The more complex, the more many parts there are to a structure, the more interdependent those parts are. It makes sense that if you lose a part of that, it's really hard to recreate it. It's like a devil's bargain thing. Like, this is the price you pay for complexity. Yeah, it's the price we pay for having our big old brains and... It's like it costs way more to fix a fancy car,

you know what I mean, than an off-the-shelf thing. Yeah. Totally. You know, I am curious, what does Rey think about all this? You know, how does this reporting change her? Because she wrote to you feeling like she had a superpower, and now you've told her that not only doesn't she, we're, we are, we pale in comparison to what most animals can do, that we are the outliers, we're the odd men out of being unempowered. Does it, did it, did it change her sense of specialness?

I mean, I don't think I feel less special. I think I feel way more connected to the tree of life. Like, oh, I got to experience this thing that like, all the other, or like so many of the other, maybe the majority of the other branches of the tree get to experience and like, how cool that, you know, it was just a fingertip but like, I'm out there with all those other guys. Yeah. Yeah, you're in good company. Yeah, you know, before this story, I would not have associated my fingertips with sea slugs in the slightest. But I hope that going forward, that is what I continue to think of when I look at my I

don't even know what sea slugs look like, I'm gonna have to go home, look at a picture of them, and then just like hold my fingertip up next to it and be like, that's me. Yeah. Producer, Becca Bresler. We're gonna take a quick break. And if you don't know what a sea slug looks like, or

even you think you do, just look it up during the break, because they're... I mean, it's like a Martian fashion show down there. So beautiful, so strange. We'll be right back with two more stories of growth. Hey, I'm Lotif Nasser. I'm Luluh Miller. This is Radiolab. Today's episode is about growth. Pumpkins that can grow 20 pounds a day.

Fingertips that miraculously grow back after they've been chopped off. Slugs that can chop off their own body and then grow the whole thing back. This growth I have at the bottom of my toenail. Yeah, so there are obviously all different kinds of growth, but it seems like they must be tied together by some underlying rules of nature. Oh, hello, Pat.

Hi, I am here. I've invaded your host intro. Okay, great. This is Pat Walters. He's our managing editor. Yeah, and whenever we get curious about the rules governing nature and the universe, we tend to call this one particular guy. Hey, old man. Hey, how are you?

This is actually very comfortable here. Let's talk all day. His name is Steve Strogan. I'm a mathematician and math professor at Cornell University. Also has a great podcast called The Joy of Why. And I asked him just like, what are the different ways things can grow? Okay, here we go. There's linear growth, a simple kind of growth, basically adding like one, two, three, four. This, if you're like me, is how that stack of magazines grows in your desk

each month. And then there's exponential growth that feeds on itself. The kind of growth that multiplies. Like one, two, four, eight. Picture each magazine on the stack giving birth to another issue of the magazine each month. No. The more of something there is, the faster it grows.

This of course is how diseases spread and pandemics happen. Now, there are kinds of growth that are faster than exponential. What's that? There's something called blow up. What's blow up? Which sounds like what it is. Something goes from nothing.

Boom. To infinity. In a finite amount of time. But Steve says this doesn't actually happen in the real world. Because we don't believe there are infinite any things in our existence. Oh, thank God.

And then there are these other kinds of growth that are a little more, I don't know, peculiar. And Steve told me about this one that completely took me by surprise and showed me how these patterns, these invisible blueprints of growth can sometimes stretch out and connect parts of the world that I didn't think had anything to do with each other. Hmm. So you've heard the name Fibonacci. There's the famous Fibonacci sequence, which is where I take a number like one and two, and then I add them to make three.

And then I always take the two most recent numbers and add them to make the next number. So two plus three is five, five plus three is eight. Where am I? Eight plus five is 13. These are all Fibonacci numbers, and you can keep keep going like that and you can see they're getting big. So the sequence goes one, two, three, five, eight, and each number in the sequence is the sum of the two that came before it.

So it keeps getting bigger in this strange and yet oddly like predictable way. Yeah. Okay. And I think when I started talking to Steve about it, I had the vague sense that like what was interesting about it is that it sort of shows up in nature, maybe in plants. Yeah. But according to Steve... The Fibonacci sequence was originally posed as a problem about rabbits growing, where

there was some made-up population biology rule about how many rabbits give birth to how many other rabbits that led to the Fibonacci sequence. That's from 1200 AD and it's not even... They observed something in rabbits? No, it's a made-up, it's a textbook problem, it's fake. Rabbits don't really grow according to the Fibonacci sequence. Wait a minute, so they came up with the, where did the sequence come from? Well, it's got a good backstory. Yeah, what's that story?

So Fibonacci, Fibonacci whose real name was Leonardo, but of Pisa, not of Vinci. Weirdly, Steve says, a historian sort of randomly stuck him with the name Fibonacci in the 1800s, but all this happened about 600 years before that, when he was still just Leonardo of Pisa. So Leonardo of Pisa, AKA Fibonacci,

is a Italian mathematician whose dad was working in North Africa. It's a really interesting, vibrant place. He's getting to meet people from Egypt and all over the Middle East, as well as Sicily. And there's a lot of trading going on. It's 1200, a very vibrant time in the Middle Ages. And this Leonardo learns about a fantastic new kind of math

that has come from a different part of the world, from the traders coming from the Middle East, from Arabic world, including who have themselves learned math developed in India. And so when we talk about Hindu-Arabic numerals, the ones that we all use today to write with, 0, 1, 2, 3, up to 9, those digits are from India by way through Baghdad

and finally into Europe through, dun-dun-dun, Leonardo of Pisa. Fibonacci brought Hindu-Arabic numerals to Europe. So this, it's a really ironic thing that Fibonacci gave us the numbers that we all use today and nobody really remembers that that's what he did. He wrote this book called Liber Abaci, basically the book of counting, the book of reckoning, how to work with numbers in a really practical way that merchants of the type that he was encountering in all these trading spots in the Middle East, everybody had to work with money and Roman numerals were terrible. So everybody wanted a better way and these Hindu-Arabic numerals were fantastic.

You could do really good calculations in your head. So anyway, he introduced this fantastic system of Indian numerals to Europe around 1200, and he just has a little footnote in his book, not really a footnote, but the book is filled with practice problems about taxes, about interest, about all kinds of money problems, but he made up this problem about growth, that the rabbits take one month to mature, and then when they mature they give birth to another set of rabbits, a pair of rabbits and then that pair can mate, blah, blah, blah.

Anyway, he made up this story about rabbits where the Fibonacci sequence comes out. But the sequence, even though he applied it to a made up story about rabbits, but don't we see the Fibonacci sequence? Yes. Represented in nature? Yeah, yeah, yeah, we totally do, sure. Plants really do have it. I mean, there's a million places we could go.

If you look at a pine cone, if you start following the straightest line that you can, you can make a certain number of windy spirals. So if you count them up, the number will end up being a Fibonacci number of these spirals. And no matter how you do it, you'll always get a Fibonacci number. So did he just wing it and throw it on some rabbits and then it turned out magically to be true? Yes, I think so. Did it come from India?

Well, okay, that's another good story. It's nice of you to keep asking me these kind of questions. Okay, so it turns out that Fibonacci was not the first to think of the Fibonacci sequence. It's a misnomer and we're only gradually starting to appreciate how much of European math is really Indian math or Arabic math. I mean, a lot of it is European. I don't want to pretend it's not. But the Fibonacci sequence was known 400 years before Fibonacci, if not longer, in India. And in

a really surprising place. It's in connection with poetry. With poetry? Yeah. Can I try to explain it to you? Yeah, please. This will take a minute. Okay, yeah, do it. We can try it. Take us there. Yeah, okay. So going way back, a few hundred years before the birth of Christ, there are scholars in ancient India who are really interested in, let's call it meter, you know, like rhythm, patterns of rhythm in poetry. The poems have certain rules to them because the rules make it easier to remember. And in a time before people had books, because remember the printing press is in the future.

Oh, right. Right? So like if you want to remember the Odyssey in ancient Greece or memorize the Koran, you're going to sing it. So it's not just because it sounds nice or pretty, it's because it's a tool for remembering. It's the way human psychology works. So these ancient scholars in India were trying to just think what exactly are the possible patterns if we obey, if our poetry obeys a certain rule which is that you can build it out of two types of syllables. You can have something

that lasts one beat or something that lasts two beats. And so one question that people interested in the sort of the science of poetry were're concerned with was, suppose I wanna make a line that is, for example, four beats long. How many different ways can I make something that's four beats? Basically, I have two things I can play with. Something that's one beat long or two beats long, right? There's these two kinds of syllables.

So I could do one plus one plus one plus one, that adds up to four. Or I could do a rhythm that plus 1 plus 1, that adds up to 4. Or I could do a rhythm that was 2 1 1, that would also add up to 4. Or I could do 1 2 1, that would be 4. Or I could do 2 2, or I could do 1 1 2. I've said five possibilities. Now, what's interesting about that is that five is the fourth Fibonacci number. And in general, if I want to make something that's N beats long, there is the Nth Fibonacci number ways of doing it.

Whoa, wait. Okay, so to make a five beat line, there would be eight ways of doing that. And to make a six beat line, there would be eight ways of doing that. And to make a six beat line, there would be 13 ways of doing that. Yes. And a seven beat line, there would be 21 ways of doing that. It's a growth problem, right? It's the growth of possibilities. It's the growth of creative possibilities in Sanskrit poetry. This was figured out in India by a person named Virahanka

four centuries before Fibonacci was born. What? Yeah. So they noticed this phenomenon present in poetry, studying the possibilities in Sanskrit poetry. And then like when I Google the Fibonacci sequence and Wikipedia tells me it's like really all over nature, not just in pinecones but pineapples and on sunflower seeds. Apparently lots of

flowers have a Fibonacci number of petals. Yes. I'm just now trying to like wrap my head around like is that because there's something in the universe that like made its way into the Sanskrit poetry by way of humans that also made its way into the trees and the pineapples and like what's the, that's crazy, that's wild because I think about poetry as being separate from a pineapple or the leaves on a tree. Yes. Well, okay.

It's not a tree. Yes. Well, OK. It's not a question. No, it's an expression of wonder, which is appropriate. Why are Fibonacci numbers in botany? Why are they in so many plant structures? There are various theories out there. Some people will say that it has to do with, like when a branch shoots out of a tree,

it doesn't want to shoot out in a direction where it's covered over by another branch. It needs to get its own sunlight. So if the branches have to grow, I mean natural selection, evolution will have disfavored the trees that don't follow this principle. That may have something to do with it. I'm not giving you a clear explanation because I don't honestly know. This is helpful. I'm not like, maybe the same thing holds true for the poetry where people are trying to create newness. You're trying to make, I don't know,

create space in a sense. Yes, you're trying to create novelty subject to constraints. Right. And you could say novelty subject to constraints is art. Like growth in creativity subject to constraints. Right? And you could say novelty subject to constraints is art. Like growth in creativity subject to constraints. That's what art is, right? Hmm, yeah.

Anyway. Huh. So what do you make of all that? I guess, I don't know. It sort of makes me see the plants as a little bit more artistic than I did before. And the poetry as like a little bit more from nature. It gives me goosebumps. That's really cool.

Yeah. You're also missing the other takeaway here, which is that Fibonacci didn't discover the Fibonacci sequence and that's not even his real name. It wasn't even that Fibonacci didn't discover the Fibonacci sequence and that's not even his real name. He wasn't even named Fibonacci. That is the point. Let's bring it back down to earth and focus on what really matters.

What really matters is that Fibonacci. He's a fraud. Let's just call him out. Is not who we thought he was. Well, thank you, Pat. That was beautiful. And we will be back in just a moment with one last growth story of planetary scale and import

and the little humans trying to control it. Stick with us. LULU Latif We are back. Okay, so, um... With one more story of growth from producers Annie McEwen. I've just detangled my headphones. And Simon Adler. But go on! Go on!

Alright, let us begin. Alright. So I think like most people, I thought for the longest time that human population was growing really fast. We already have between three and seven times more people than we can permanently support. Maybe exponentially. The growth rate is just incredible. You know, people were popping kids out and blah, blah, blah.

We are destroying our fossil fuels. We are dispersing our mineral resources. And that this was like a really big problem. We're freaked. Yeah, a ball of flesh expanding at the speed of light, I think. A ball of flesh expanding at the speed of light. Oh, God. This is Phillip Cohen.

I'm a professor of sociology at the University of Maryland. And I called him up to talk about this fear. It was one that I really took deep into my soul at some point in my life. And he told me that, like, yes, this was a real concern starting around the 1950s. Population did start increasing exponentially, you know, 2 billion, 4 billion, 8 billion. Population bomb kind of thing. Yes. Yeah, yeah, yeah.

But by the time I had even started worrying about it. By the 90s, really. It was no longer a problem. Right. You know, it's obviously a long, complicated story and it's different around the world. But with better healthcare, better contraception, and access to education, a lot of women started having fewer children. Fewer kids meant slower growth, and as growth slowed, demographers predicted that population

would just plateau. Yes. The idea was that the average woman was going to have two children, and that world population would hit a peak around 10 billion around 2060 or so, and after that be stable. And we would all live happily ever after. Oh, thank God! Yeah, it's great.

Big ol' exhale for Annie McEwen on the population front. Okay, that's right. But then, like 10 seconds after I learned about this plateau and felt great about it, I learned that that is not what's happening. Well it would be in Europe that panic first started. Because instead of like watching things come to settle at a peaceful plateau, demographers notice that, especially in Europe, but also in other parts of the world, you know, South Korea, China, Japan, that this drop in birth rates, it accelerates. The fall accelerates.

Exactly. Oh. Birth rates in a bunch of places were now dipping too low. Okay, so I've got the latest fertility rate information here in front of me. So like ask me, ask me a country and I'll tell you. Okay, France, France, France. Okay, so remember for us to keep replacing ourselves, the number to hit is 2.1. France is 1.8.

France is 1.8. Okay, au revoir. Poland. Poland is 1.5. 1.5, wow. Yeah. Mexico? Mexico. 1.8. Okay, au revoir. Poland. Poland is 1.5. 1.5, wow. Yeah. Mexico? Mexico.

1.8. Cameroon. 4.29, so they're above replacement. Oh, they're high. Yeah, they're high. They're high. But they're falling. Like in the 80s, I think it was 6.7. Whoa. What about Ghana? 3.5, but they also fell from over 6.

Oh, wow. Italy? Italy's 1.3. Italy's low Whoa, he's 1.3. Wow Yeah, what are we what's the US 1.7 1.7? Yeah Wow and um, where's it? The lowest the lowest are like Korea. Yeah in Japan, which I think Korea's at like 0.6 Japan, which I think Korea is at like 0.6. No. 0.6, 0.7. Yeah.

Wow. That's so low. Wait, and Earth as a whole is what right now? It's 2.3. So we're just above total. Wow. Yeah. And Philip says that this downward trend is going to continue.

The world population is going to hit a peak around 10 billion around 2060 or so and after that it will almost certainly start to taper downward. So we are on the verge of beginning to shrink. Really? That makes me so happy! Yes! In a couple hundred years it's projected that the Earth's population will actually be about six billion. Wow!

That far down! So less than now. Oh, yeah. We were going on a roller coaster and we're like, we're coming at that, we're like... It's like the tukka tukka tukka on the roller coaster before the drop. Exactly. I am really pumped to hear that. Whoa! I don't know, I think I kind of before the drop. Exactly. I am really pumped to hear that. Whoa!

I don't know, I think I kind of like the plateau. The plateau sounds so nice, because the stability, it's like you can, you know what to plan for. Like you know what to... But it's the stability of like, of a hurting earth and like strapped resources. How about a little less of us? Oh, that's fair.

To drive cars and share wheat. That's fair, but I don't know, there's something that sounds sad about less people. It's like the party's ended. No. Like it's like the party is... Absolutely not sad. It's like... It's great.

The parties, there's still so many people. The club is popping. Yes, the club is popping. Yeah. I think when I heard this, I was like, okay, great. I feel relieved. The skinball is not going to happen. But I guess the thing that I was most struck by is just, well, I was like, okay, great. I feel relieved. The skinball is not going to happen. But I guess the thing that I was most struck by is just while I was freaking out about

humans exploding off the planet, eating everything, there was a whole other group of people freaking out about the exact opposite. Really? Why would they be worried? Well, you know, some of them are the gabillionaires. You know, if we don are the gabillionaires. You know, if we don't make enough people to at least sustain our numbers, perhaps increase a little bit, then civilization is going to crumble.

Who are just like, let's grow, grow, grow so we can all make more money. I'd rather civilization went out with a bang than a whimper and adult diapers. But then they're like also regular economists, especially in like the Western capitalist economies, who say that the shrinking is a problem because our economy needs workers to just, you know, keep things chugging along. But I mean, what about immigration? Forget all the other reasons. Just looking at it from this economic viewpoint, I mean, people in the United States might not be having that many kids, but there are lots of people who would love to come and live here and therefore be workers in the economy.

Yes. Anybody who says there's a population shortage or problem in any rich country has to at least answer the question of, what about immigration? Like, were it not for immigration, the US population would be falling right now. Really? Yes, or it would be falling very soon.

Which is so crazy that the administration in power right now, the whole thing is like, get people out, get people out. It's like, yeah, we kind of need people right now. Yeah. And actually, when I spoke with another demographer on the phone, James Ramo, he told me that all these countries that are really not immigrant friendly, in 50 years time, they're going to be fighting to attract immigrants. Oh, I bet. I bet.

But like even with all these wealthy countries holding their doors wide open, that's only a temporary fix. That works for, you know, maybe 100 years or maybe 50 years. Because by the year 2197% of the world's countries will be below replacement level. So this sort of decline in fertility is happening everywhere and it's happening more slowly in some countries than others, but it is happening. So basically in 70 years or so, most of the planet will be dipping. Yes. And like I think talking about the economy, especially the economy in the future, it felt

just very abstract. But for me, the whole thing started to get kind of unsettling when I called up another demographer. Hello? Oh, I hear them. Hello. This one named Leslie Root. I am assistant professor of research at the University of Colorado Boulder.

Who told me that fundamentally, this whole thing is a question of how will we care for each other? So this is true of any human society, right? That you have people who need to be supported and you have people who are capable of supporting. And people who need to be supported are the very young, right? Human children are pretty hopeless. And compared to other primates, They can't do anything useless. Yeah, exactly. And the elderly.

And then sort of the prime working years is when we are supposed to be able to produce more than we consume so that we can share it with other people. And so a big concern is that when you have lower fertility, and imagine your population with like people flowing into and out of it, fewer people are flowing in and the people who are already in it are getting older and older. So you have what's called an aging population. So like in 200 years when the population is down to six billion, that's going to be a

very different six billion than the one we just experienced in the year 2000. Because a lot of those people are going to be very old. And the worry is that as society becomes more and more top-heavy... What does that mean for our ability to support each other? Just super practically, who are all the doctors going to be to take care of these old people? And who's going to staff the nursing homes? And who will grow the food to feed these old people? You can sort of see that as the proportion of feed these old people? Like, you can sort of see that, like, as the proportion of young to old people shifts more and more out of whack,

you have on the backs of these few young people kind of the burden of everything. Unless... Fatte fili, fatte fili. A whole bunch of us right now... The pope told Italians to have more babies. Start to breed like rabbits. Which is what a bunch of governments around the world are trying to get their citizens to do.

Putin has urged Russian women to have eight or more babies. Here's a bunch of stuff that countries have tried. Japan tried government-sponsored speed dating night. Russia, they're like, hey, if you have more than two kids, we'll give you $7,000. About 10 times the average monthly wage. Funny. Russia, they're like, hey, if you have more than two kids, we'll give you $7,000. Right. Taiwan, there was a presidential candidate in 2023 who was like, hey, everyone who has a baby should get a free pet as well. A free pet?

That's like more, more work. There's also things like Sweden has this amazing parental leave policies. 480 days. Germany's got free daycare. That's money. Big. using parental leave policies, Germany's got free daycare. That's money. Big. And of course, there have also been some darker attempts to control, like in the US and North

Korea where abortion has been banned. But the crazy thing is that like carrot or stick, none of this has worked. None of it's worked? Yeah. And the one thing I'll add to that is like with few exceptions, and the exceptions are sort of explainable away, no country that has dipped below replacement rate has ever gone back above. Wow. Interesting. Right. There really is no success story out there.

Nobody has shown how you can turn this around. Huh. That's wild. I mean, do people have any idea why not? I don't know. I think it's because it's just really hard to answer the question, why does someone choose to have a kid or not?

Yeah, there's a lot of casting about for explanations of what exactly drives lower fertility. There are going to be a hundred reasons, big and small, why someone becomes a parent or not. You know, we meet a partner or we don't, and our partner has the same preferences that we do or they don't. We can find affordable housing or we can't.

We have access to great health care or we don't. We get a good job with flexible hours or we don't. We live near family who can babysit the kids or we don't. We get a good job with flexible hours or we don't. We live near family who can babysit the kids or we don't. You know, for every one person, the decision is going to be this like really complicated mess of reasons and circumstances. And if you zoom out from there to the national or like the global level, looking down and trying to understand this is just total chaos. Hmm. Right. trying to understand this is just total chaos.

Hmm. Right. You're not going to solve the mystery of why. And basically there's nothing you can do about it. So what does this look like? You know, like what does it look like when a society stops having children? This is Gideon Lewis Krauss. I'm a staff writer at The New Yorker. He recently wrote an essay about declining population called The End of Children.

And as he was starting to report the piece, he noticed that there were all these articles in Western media about South Korea. Obviously South Korea with the lowest fertility rate in the world comes up all the time in all of these columns. And I noticed that everybody invoked South Korea, but it didn't seem like anyone had gone there. And I thought it would be interesting to hear from some South Koreans about this. South Korea is a country that has more deaths than births every year, and it's not an easy

country to immigrate to. So its population is getting older and smaller. And so it's sort of seen as almost like this bellwether for where the rest of us are headed. And so I got there and I got into the center of Seoul and I went to the subway at rush hour and you saw no children anywhere. But at first I thought like, oh, well, you know, in New York, like, would I take my kids on the rush hour subway? Like, probably not. But then pretty immediately, like, you really just don't, you know, you don't see playgrounds

or like the handful of playgrounds that I saw were completely empty at any time of day. And you just don't see a lot of children. And there were these no kids zones everywhere. There were signs on restaurants and other establishments that said no kids here. And I mean, so much of it is about a rapid shift in cultural norms about kids. So in fact, I met with this young economics reporter who writes about this for a living, and she was in her early 20s, early 30s. And she said, like, I understand all of this stuff on a deep economic level.

But when I write about it, I think like, well, what would change my mind? And the answer is nothing. There's nothing that would make me want to have kids because it's the norm to not want to have kids. Gideon eventually made his way out to some of the more rural areas of the country, where it's projected that about 2,000 schools are going to be closing in the next 10 years. And so I wanted to go visit one of these schools. So I went to one in the far south. And this school, I think it had as max it had about 1300 students. Now it has five. It had with five students, five students. Yeah. What grade it had three first graders and two sixth graders. And when I was talking to the sixth grade teacher, I said to him like, so you have two kids, like, do they get along?

And he, like, looked at me like I was a complete idiot. And he was like, what do you mean, like, do they get along? Like, they don't know anyone else. They've been in school together since they started school. Like, the other child is, like, the only other child they know. Hmm. What was it like walking through this school? Like, what did it look like? Well, there, you know, there's a feeling of great dignity and resignation about this stuff.

So, the outside of the school had been freshly painted and the inside was bright and totally broom swept and spotless and everything was in perfect order except it was empty. And like there was no heat on in the hallways. And almost all the classrooms were dark. And some of the classrooms had photos of the last group of kids that occupied that classroom. The classroom was dark and just hadn't been opened in a couple of years. And the cafeteria had a little proscenium stage

with a curtain and clearly they had had school plays there and stuff and you probably could have seated 300 people in this cafeteria. So it just felt like everyone had eva... Like, there was no sense of decay. It just felt like everyone had evaporated. Right. It does feel like children are disappearing. Yeah. And... And something like 200 nursery schools have been converted into retirement homes because there's like a radical dearth of retirement homes. And you can see that some of these nursery schools that have been turned into retirement homes, they've kept the same directors and

they had kept the same like rubberized play floors for the old people and they even had Actually my fact-checker Emily found this when she talked to them She was like not only do we have the same rubberized play floors We have the same crayons that like the kids used to use the crayons, and now we just like the seniors use the crayons. There's something really dark about that. Yeah.

Yeah. Yeah. The bell curve of life. But... this is our projection. Yeah. We've already in this very, been wrong twice about projections. We thought, oh my God, it was gonna be a population bomb explosion, too many people.

Then we were like, oh, it's gonna level out so nicely, perfectly. That didn't happen. How do we know that these projections are worth anything? Yes. That's a great question. That is a great question. I think that we just don't know. We just don't know what's gonna great question. That is a great question. I think that we just don't know. We just don't know what's going to happen next. But what we're heading towards is really unprecedented.

And there is no way to be like, oh yeah, last time this happened. So we can project forward and imagine. And I do think that- The last planet we were on. And as fewer people have fewer kids, those fewer kids are going to have fewer kids. And this is just mathematically, it seems tricky to get out of that spiral. However, we totally don't quite know. And I think that's very fair.

What is very much agreed upon is that the population of the world is going to start declining. And that is a totally new thing for humanity. And that is set to happen pretty soon. Yeah, yeah, pretty soon. I hope to live to see it. It's just interesting to imagine being on the planet and sort of looking around and being like, this is the most people there might ever be alive at one time. At that moment, yeah. It's big. It's like, yes, it's like going to the moon or, you know, our first nuclear bomb. I mean, it's a big moment in human history when we turn that around,

and for the first time the global population is declining. The feeling like you might never come back from it, like you've changed direction. Yeah, it's a shift from growth to something else, something new. Right, exactly. Producers, Annie McEwen and Simon Adler. So that's the end of the growth show, a story about shrinking. Yeah, yeah

from a pumpkin that was kind of growing uncontrollably to a population that seems to be shrinking uncontrollably. Well at least we're making room for more giant pumpkins. There's always that, the silver lining, the orange lining. That I guess is our show. This episode was reported and produced by Matt Kilty, Becca Bresler, Pat Walters, Sindhu Nyanasambandhan, Annie McEwen, and Simon Adler with additional reporting by Ray Mondo. And it was edited by Pat Walters. Mixing and sound design by Jeremy Bloom, fact-checking by Emily Krieger and Natalie Middleton,

and special thanks to Ellie Tanaka, Keith Devlin, Devin Patel, Chris Golay, James Ramo, and Jessica Savage. I'm Lula Miller. And I'm Lutif Nasser. Thanks for listening. Thanks for listening. I'll see you soon. Hi, I'm Paolo Marabigs and I'm calling from Nuuli, American Samoa, and here are the staff credits. Radiolab was created by Jad Abumrad and is edited by Soren Wheeler.

Lulu Miller and Nathap Nasser are our co-hosts. Dylan Keefe is our director of sound design. Our staff includes Simon Adler, Jeremy Bloom, Becca Brestler, W. Harry Fortuna, David Gabel, Maria Paz Gutierrez, Sindhu Namasamandam, Matt Kiyoti, Anna McEwan, Alex Neeson, Sara Khari, Sara Sandbach, Anisa Vitsa, Ariean Whack, Pat Walters, and Molly Webster. Our fact-checkers are Diane Kelly, Emily Krieger, and Natalie Middleton. Baputai Telelava, Malo.

Hey, I'm Steph. I'm from Melbourne, Australia. Leadership support for Radiolab's science programming is provided by the Gordon and Betty Moore Foundation, Science Sandbox, Assiamon's Foundation Initiative, and the John Templeton Foundation. Foundational support for Radiolab was provided by the Alfred P. Sloan Foundation.