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

September 1, 2026

AI Summary

5 min read

A four-to-six-month-old infant was buried 74,000 years ago in a rock shelter called Border Cave in South Africa. In the grave, the child was wearing a pendant made from a single, notched cone shell—Conus abraeus—that had been strung and worn by someone for many years before being placed with the baby. That shell, as science and environmental journalist Cynthia Barnett tells it, is the earliest known shell deliberately buried with a human. It is also a reminder that seashells have always been more than beach souvenirs: they are the durable homes of marine mollusks, and they carry information about both human history and the changing chemistry of the oceans.

Shells as recorders of human history

Barnett’s book The Sound of the Sea grew out of a disturbing fact she learned while giving a talk at a museum on Sanibel Island, Florida: most visitors thought seashells were rocks. They did not know that every shell is built by a living creature—a marine mollusk—out of calcium carbonate from the surrounding seawater. That misunderstanding bothered Barnett enough to write a whole book about what shells actually are and what they can tell us.

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What you'll learn

1 (00:36) **Introduction: The Hidden Life of Seashells** - Host Emily Kwong returns to introduce the episode's focus on seashells as more than just pretty objects.
2 (03:35) **The First Shell Adornment: A Stone Age Baby** - Barnett describes the earliest known shell buried with a human, a cone shell from a South African cave.
3 (04:32) **Shells as Historical Fact-Checkers: The Calusa Shell Works** - Barnett explains how ancient shell mounds in Florida were not trash heaps but monumental structures.
4 (06:40) **From Shell Shop to Global Oil Empire** - The story of Marcus Samuel, a Victorian London curio shop owner who built a fortune on seashells.
5 (08:49) **The Core Irony: Fossil Fuels Harming Shell-Makers** - The direct link between the oil industry's origins and the damage it now causes to marine mollusks.
6 (09:32) **The Mechanism: How Shells Record Climate Change** - Barnett explains how mollusks build their shells and why this makes them sentinels of ocean change.
7 (10:44) **Unsung Shell Scientists: The Story of Mary Anning** - The episode highlights the overlooked contributions of women in conchology and malacology.

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Show Notes

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 [email protected].

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