In parts of Papua New Guinea, people still pay with strings of shells

On the islands of the Bismarck Archipelago in Papua New Guinea, a traditional currency called tabu — small shells from a specific type of snail, strung together on long cords — has been in circulation for generations.

The twist: this isn't a museum relic, it's a living, parallel payment system — tabu is still used alongside the country's official currency (the kina) to pay dowries, tribal fines, or settle local trade, and its exchange rate against state money is sometimes even set informally.

The value of tabu depends on how rare the specific shell species is and how labor-intensive it is to gather and string — the longer and more uniform the cord, the more valuable it is, much like precious metals.

The stakes: the coexistence of two completely different monetary systems in one country shows that a currency's "realness" depends purely on whether the local community agrees to trust it — whether it's backed by a central bank or by a custom passed down for generations.