Short Wave - What can seashells teach us about the health of our oceans?

Episode Date: September 1, 2026

Seashells: They're beautiful remnants to carry home from the beach—and so much more! According to environmental journalist Cynthia Barnett, seashells record history more accurately than the humans who first wrote it down. In this episode, we talk about the science of seashells, their impact on humankind and the scientist behind a very famous tongue twister.Check out Cynthia’s book The Sound of the Sea and check out Emily’s reporting on sandcastles.Interested in more marine biology stories? Email us your question at [e-mail] public media with NPR+ and enjoy perks for over 25 podcasts like this one. This show’s hperks include sponsor-free listening. Learn more at plus.npr.org. See pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

Hey, Regina Barber here with a request. Follow us on whichever app you're listening to. We love sharing cool and important sign stories with you. And following us means you'll always know when our next episode is ready. Just like this one. You're listening to Shortwave from NPR. Hey, Shortwavers, Emily Kwong here. I have been away for the summer working on another project. But I'm back for today with a little treat, an ode to seashells. One of the most famous places in the world to collect seashells is Sanibel Island off Florida's Gulf Coast. And a few years ago, science and environmental journalist Cynthia Barnett was giving a talk at a local museum on Sanibel Island. When the director told her a fact she found totally depressing. The vast majority of visitors, like 90%, didn't know that a seashell was made by a living animal. most people thought that seashells were some kind of rock or stone. And I was so kind of disturbed by that fact. I

kept tossing and turning that night thinking about that statistic. And by the time I woke up the next morning, I knew I wanted to write a book about seashells. That book became The Sound of the Sea. And across its pages, I learned that even though people have long been drawn to seashells, they're built by and for marine creatures. A seashell is a home and protection to these wonderful soft animals called marine mollusks. Conches, cowries, cones, all these seashells are created by something living. So today on the show, eavesdropping on seashells. What hidden clues these calcium carbonate houses hold about the state of our oceans and why

seashells have always been a part of Earth science. I'm Emily Kwong and you're listening to Shortwave from NPR. All right, Cynthia, so let's get into the book. Starting with, I hope I say this right, conis ebraeus. Yes, conis abraeus. Thank you. Thank you. This is a small cone shell that is the earliest known keepsake buried with a human. What is the story of this first shell? This stubby cone shell was unearthed from the grave of a four to six-month-old infant in a large rock shelter in South Africa known as Border Cave. And it had been notched by hand and strung onto a pendant and worn for many years before it was ever placed with the Stone Age baby. And I just, as a mother like that, that detail is so poignant to me. And I have thought so much about who, you know,

mother or father might have worn that shell before placing it in the grave with their infant. Yeah. All right. Before we get into the present day, just going back in history a little more, I learned from your book that shells can also be used for construction. You're from Florida, and that's the home to the Calusa Shell Works. What are those? Yeah, so the Calusa were native Floridians who lived in southwest Florida. They built these extraordinary shell mounds. They rose here in Florida like temples in the ancient world. And they were built by the Calusa more than 1,500 years before the Spanish arrived.

And early scientists kind of considered these middens garbage heaps of nomadic people, but that wasn't the case at all. These shells were homes and sands. sanctuaries and public buildings. And they also had these incredible shell work factories. Wow. So these shell mounds weren't garbage heaps at all. Emily, I came to think about shells as the world's great fact checkers. Like the people who wrote history would have us think certain things about Native Americans, but the shells tell otherwise. There were major pre-Columbian states.

cities on U.S. soil, and these mounds just make so clear that the new world was hardly new, much less settled by bearded men on sailing ships. So it's like, in a lot of ways, shells are more accurate recorders of human history than the humans who first wrote it down. And that's something I love about shells. Yeah, they hold a lot. And how are they doing that? I mean, is just because of the material? It's because they're so strong. And, you know, just think about the limestone underfoot that forms our aquifers is made from the shells of marine life that lived millions and millions of years ago. Absolutely. Yeah. It's amazing to think about. And our history with shells stretches millions of years later with people finding them in South Africa. You mentioned

in the border cave, in Florida, and even in England. So without giving anything away, I want you to tell us that one story from your book featuring a gentleman in Victorian England who found a way to make money off of people's obsession with seashells. Take it away. Yes. In the 1830s, there is a curio shop owner in the east end of London named Marcus Samuel, and he is importing seashells from Japan and selling them. And he had the idea to come up with these little shell-encrusted boxes to sell tourists in Brighton and other beaches all along the coastline. And that is how he really, he really made his fortune.

What began as Marcus Samuel's tiny shell shop became one of the largest oil companies in the world, shell oil and transport company. That's wild. So the Samuel Sons in the second generation started trading other goods with Japan, including kerosene. And they were trading kerosene and needed a way to hold the kerosene that they were going to send through the Suez Canal. And that led them to create the very first shell oil tanker. And they named that first oil tanker, Murek. which is a wonderful iconic shell from history. They named that first oil tanker Murex in 1892 in honor of their father.

Though this is a surprising fact, what's consistent here is that somebody was leaning on the natural world to make money. The beauty of the shells became a profit. And in the case of shell oil today, the energy, density of the fossil fuels is creating a profit. But fossil fuels, of course, are a product of nature. We just forget that. Absolutely. I have written that shell oils tankers are not large enough to hold this irony. It is just extraordinary. And the irony, you know, begins with the damage being done to the oceans and the earth by fossil fuels. But it's even more directed than that in that marine mollusks and their shells are being harmed by the impacts of climate change

on the oceans. Yeah. Explain that further. How do seashells carry evidence of climate change? They build their shells with minerals from the surrounding sea, primarily calcium, carbonate. They're putting down layers of shell as they grow, their shell grows. And it's their reliance on those minerals that makes them sentinels for what's happening to the oceans now in a changing climate. So too much carbon dioxide in seawater causes chemical reactions that reduce pH and the carbonate concentration. And that is making it harder. for mollusks to build their shells. Parts of the oceans are becoming too warm for the native mollus that have always lived there. So it's two things. The chemical changes are making it harder for them

to build their homes. And the oceans are becoming too warm for mollus to live in some parts of the sea. Yeah, it's amazing how this shows up in seashals. Which we know because of the work of scientists. There's a long history of ocean science. And as I learned in your book, seashell science. Yeah, absolutely. Yeah. And you write about how it's work that women have long contributed to,

but they haven't always been recognized for their seashell discoveries. Can you tell us the story of one such scientist, Mary Anning? What's her story? Mary Anning. She's kind of more well-known now. but Mary Anning grew up in Dorset, England, to a family that sold curiosities and fossils along the rocky coastal cliffs to make a living. And she was an extraordinary taxonomist who, she actually discovered two major species of dinosaurs,

the ichthyosaurus and the pleasiosaurus, without any credit or compensation. Casual? Okay. And she also as, yep, yep. She also knew a lot about fossil shells and detailed the taxonomy of fossil shells. And scientists would come from universities to buy shells from her and learn about shells, fossil shells, without ever crediting her. So I really tried to elevate some of the important women in conchology and malacology. Yes. And we also have Mary Anning to thank for one of the

the most famed tongue twisters of all time. So can you say it three times fast? Yes. She sells seashells by the seashore. She sells seashells by the seashore. Seashells. I blew it on the third one, Emily. In fairness, I should be forced to say it too. Maybe I'll try it at the end of the episode. But last question, Cynthia, now that you've written this book, what have you realized about seashells and why it's important to understand them as more than just? beautiful objects. When I was a little kid in Florida and also in California, we would pick up shells and hold them to our ear. I did that too, and I'd say I can hear the ocean. And my parents would say it's the blood in your ears, but it didn't feel like that. I'm sorry to say that

your parents were closer to the truth. We're not hearing the oceans. But, What I think is so beautiful and profound here is that seashells did have something to tell us. We were picking them up. We were trying to listen. And they really do have something to tell us about the way we're living and what human activity is doing to the sea and all of the earth. Cynthia Barnett, thank you so much for talking. to me. This's been so fun. Thank you, Emily. Great talking with you. Hope to run into you on a beach somewhere. Okay, shortwavers, if you want more beachy science, there is an episode I reported a few years ago on the science of sandcastles. Have you ever wondered how they are held together? Well,

look no further. Check our episode notes for that and maybe send it to a friend to, you know, give them the joy of shortwave in their life, like sunshine on the beach. This episode was produced by Juan Diego Ramirez and edited by Rebecca Ramirez. Tyler Jones checked the facts, and Jimmy Keely was the audio engineer. I'm Emily Kwong. Thanks for listening to Shortwave from NPR. She sells seashells by the seashore. She sells seashells by the seashore.

She sells seashals. I was getting arrogant. I got too fast.