Cynthia Barnett reveals the secret lives of seashells in ‘The Sound of the Sea’

The environmental journalist and UF professor explores the fascinating history of mollusks and their interactions with humans.
"The Sound of the Sea" is the latest book by Gainesville author Cynthia Barnett.
"The Sound of the Sea" is the latest book by Gainesville author Cynthia Barnett. [ W.W. Norton ]
Published July 1, 2021|Updated July 1, 2021

At several points in her enthralling new book, The Sound of the Sea, Cynthia Barnett warmly recalls her memories of shelling on Sanibel, the southwest Florida island long a mecca for seashell collectors.

It’s the home of the Bailey-Matthews National Shell Museum, and Barnett drops a shocking statistic gathered in a survey of visitors there — people presumably interested enough in seashells to go to a museum full of them.

“The survey,” she writes, “revealed that 90 percent of the visitors had no idea that a shell is made by a living animal. Most people thought they were stones.”

Barnett is here to correct that misconception, and do much more. In her 2016 book, Rain: A Natural and Cultural History (longlisted for the National Book Award), she examined that natural phenomenon in both scientific and human terms.

Related: Read a review of Cynthia Barnett's "Rain."

Barnett, an environmental journalist who teaches at the University of Florida, follows a similar strategy in The Sound of the Sea, offering readers a fascinating history of the shellmakers and of the multitude of ways they have interacted with and shaped human beings.

“We walk on a world of shell,” Barnett notes, and not just at the beach. “Shelled plankton and corals and mollusks made some of those oil reservoirs. ... They made the limestone aquifers that hold fresh water underground. The calcifying life-forms gave us mountains and they gave us marble.”

They show up not just in our clam chowder but in everything from concrete to toothpaste, and they are one of the most significant canaries in the coal mine of climate change, if we only pay attention.

These creatures have been on the planet far longer than human beings and, after a fashion, helped to create us. Barnett recounts the discovery in Alaska of minuscule fossils of organisms that, more than 500 million years ago, learned the process of biomineralization, constructing hard structures around their bodies from minerals in the environment. We mammals use the process to build our bones and teeth, but shelled creatures built their homes with it hundreds of millions of years before mammals showed up.

Those shelled microorganisms were the ancestors of what is now the second-largest group (after insects and other arthropods) of animals on the planet. Mollusks — including gastropods, bivalves and cephalopods — encompass about 85,000 known species and countless more unknown or extinct. They live almost everywhere, from the Himalayas to the Mariana Trench, and range in size from microscopic snails to giant clams, which can top 500 pounds.

Almost all of them live in shells, in a dazzling array of sizes, shapes and colors, all of them built, layer by infinitesimally fine layer, by the animal inside. Big, showy shells like the Queen Conch begin as the tiny tip at the top of the mature shell, growing as the conch inside does, following the same intricate encoded architecture as all its ancestors.

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We might think of mollusks as stationary, like an oyster fastened to its bed, but Barnett describes a wide range of behaviors, including swimming, crawling, hopping and somersaults. Some mollusks are filter feeders, others grazers on seagrass or algae.

But some are predators, like the cone snail. Its 3-inch cylindrical shell looks harmless enough, but when a small fish ventures near, Barnett writes, the snail extends its proboscis and “plunges the tip of the appendage — it is armed with a teeny harpoon — into the fish’s belly. In a split-second explosion of sand, the cone snail opens a soft, gaping maw at the tip of its shell, draws in the struggling fish head-first, and swallows it whole.”

Cone snails also make “an arsenal of neurotoxins” — and one of those toxins was used by scientists to develop a pain drug, Prialt, that is “a thousand times stronger than morphine.” That’s just one of many interactions between humans and mollusks cataloged in the book.

Discovery of fossil mollusks was foundational to the development of scientific understanding of evolution, extinction and geology, Barnett writes. The long changes on the Earth’s surface are often marked by seashells, left eons ago in places now far from the seas. As writer John McPhee once noted, “The summit of Mount Everest is marine limestone.”

Humans have long consumed the animals that build shells, and Barnett writes that their rich protein and mineral content might have contributed to our development of bigger brains.

As far back as the Stone Age, archaeological evidence tells us, shells were traded across and among continents, as ornaments, tools, religious objects, musical instruments and more. One of the most resonant histories Barnett includes is that of the Money Cowrie, a domed shell that originated in the waters around the Maldives, a remote island chain off India ruled by legendary queens. Via sailing ships and overland trade routes, the cowrie became a form of money used as far away as West Africa, where it was the common coin of the slave trade.

Shell collecting has seen countless surges, Barnett writes. An extensive collection, rumored to be that of Pliny the Elder, was found in the ruins of Pompeii. Shells were obsessions for Leonardo da Vinci, Queen Victoria and Emperor Hirohito; Marie Antoinette had a shell-encrusted cottage near Versailles. Ever wondered how Shell Oil came by its scallop-shell trademark? It’s an amazing story.

Barnett also includes mini-biographies of some of the scientists and writers most closely associated with shells, such as Georgius Rumphius, Thomas and Lucy Say, Julia Ellen Rogers and Anne Morrow Lindbergh.

Barnett herself travels the world to tell her story, as far as the Maldives and a “door of no return” in a port in Ghana from which enslaved people were shipped to the Americas.

She also circles back to her home state of Florida. One of its indigenous peoples, the Calusa, lived along the southwestern edge of the peninsula for 1,500 years, traveling by canoe and building “a coastal empire.” Most of their food came from the sea, and they used shells as tools and trade goods and as building material for communities of as many as 20,000 people.

Some of their larger cities were on and around Pine Island, between Sanibel and the mainland. In 1895, pioneering anthropologist Frank Hamilton Cushing was stunned to find a complex of shell mounds, pyramids, water courts, burial grounds and canals extending for over a mile and a half on just one island. Some mounds were more than 60 feet tall. His one-day sail to Marco Island turned into eight days as he found more and more ruins.

To the north, around Tampa Bay, the Tocobaga, another tribe, built their own shell cities. But today, outside of small preserves, only traces are left of any of them. In the 20th century, Florida’s flood of new residents prompted developers to level those enormous mounds, scooping up shells (and artifacts, and skeletons) by the ton to fill swamps, lay roads and build up construction sites above the perennial floods.

If you lay your head down tonight somewhere on the gulf coast of Florida, you may well be sleeping over those native peoples’ bones, and the billions of shells from which they built their cities.

The Sound of the Sea: Seashells and the Fate of the Oceans

By Cynthia Barnett

W.W. Norton, $27.95, 432 pages

Meet the author

Cynthia Barnett will discuss and sign The Sound of the Sea at 4 p.m. July 11 at Tampa Bay Watch, 3000 Pinellas Bayway S, Tierra Verde. Book sales by Book & Bottle. The event is free; register at

Barnett will appear virtually, in conversation with historian Jack Davis, winner of the Pulitzer Prize for his book The Gulf, at Tombolo Books at 6:30 p.m. July 20. For a link, register at