How would you envision the perfect beach day? Your answer sets you firmly in one of two camps: shell hunter, or someone who inexplicably walks straight past them. To the former, welcome. I've lost entire afternoons to raking my nails through sand and peering into rock pools in search of the perfect specimen which, as any of us will tell you, is almost all of them. The fan-shaped scallop, the common mussel, the winding whelk: each one a tiny piece of treasure, and the fistful in your pocket by sunset your bounty.
But why are we quite so drawn to these little (and occasionally not so little) casings? As it happens, the habit is far from frivolous. It goes back thousands of years, and it says rather more about us than you might expect.
Delve into the history books and you'll find seashells were among the world's earliest currencies. Cowrie shells were money in China as far back as the Shang Dynasty, so woven into daily life that the Chinese character for money, 貝, is the cowrie itself. They bankrolled the Ghana, Mali and Songhai Empires of West Africa for centuries, turned up as clam and whelk wampum among Indigenous peoples in North America, and became shell money in Papua New Guinea. For much of the ancient world, a shell was worth considerably more than the pretty thing we now nudge about with a toe.
Though, their power wasn't purely financial. In Greek mythology, shells stood for fertility, femininity and divine birth. Aphrodite, so the story goes, drifted ashore in a scallop shell having been born of the sea, the image Botticelli made famous in The Birth of Venus. African spirituality gave cowries a similar weight, tying them to Mami Wata, the water spirit. And by the 18th century, Europe's appetite for exotic shells had tipped into full mania, so much so that someone bothered to name it: conchylomania. Shells became some of the most coveted objects money could buy, occasionally outpricing a Dutch master, before we set our sights on branded items from luxury labels.
The truth of what a shell actually is, though, isn't quite as beautiful as the mythology makes out, despite being incredibly impressive. Every true seashell is an exoskeleton: not a house some creature moves into, but a body case the animal grows itself. Molluscs like snails, clams, oysters and scallops build them using an organ called the mantle, which pulls calcium and minerals from the seawater and lays them down, layer by patient layer, into a sort of second skin. The hermit crab, that well-known freeloader, is the exception, moving into empty shells rather than going to the trouble of making one. Lazy, but you have to admire the economy.
Which brings us, finally, to the patterns we fall so hopelessly for. The spots, stripes and spirals are dictated by each animal's diet, the water temperature, the minerals to hand, the pH, and the pigments its mantle produces. And here's the part that tips it over the edge: mathematicians and computer scientists now study these patterns as evidence that dizzying complexity can grow from the simplest of rules, the same principle sitting underneath modern computing. A whelk, in other words, has been quietly running an algorithm for a few million years.
So the next time someone raises an eyebrow at the fistful you've arranged on the sun lounger, you can tell them, with total sincerity, that it isn't just shells. It's ancient money, mythology, biology and mathematics, all sitting in the palm of your hand. Frankly, it would be strange not to pick them up. Just be sure nothing is still living inside when you do.