Civilizations have been creating currencies since the dawn of history. A pure barter system always has deficiencies, not least of which is transporting goods over mountains, through valleys, and across oceans. Think of the human effort involved in a simple transaction—not to mention the manure abatement fees—on ox-drawn wagons. So, to make transactions a bit simpler, almost all civilizations have come up with currencies.
From China to Africa to the Americas, shells were used as a medium of exchange. Whether small cowry shells or larger conchs, gathered in bags or tied together to form belts, shells held value in ancient cultures. Most shells used for currency throughout the world were not large decorative items, but small, transportable, and rather unremarkable specimens. In some cultures, the time and effort spent on tying the shells together to form belts, necklaces, and tapestries contributed to their value. Shells were so predominant as a currency that some of the first real coins minted in China were bronze pieces cast in the shape of small shells.
Let's face it, it's tough out there being a chief, especially on a small Pacific island where the resources are scarce and the people are hungry. The only way to project power is by wearing a pimp-tastic feather cape that conveys authority. Feathers, then, became a prized commodity in many island societies of yore. Eventually, however, feathers themselves were being used very little in the decorative arts and instead became a mode of exchange. As recently as the 1970s, some small island communities were still using feathers bound together in plates in intra-island trading.
OK, to be fair, wampum could be lumped into the "shells" category, but it wouldn't have told the whole story. Wampum is a general name for a variety of shell beads that were produced by Native Americans from the 16th to the 18th centuries. Between various tribes and groups, wampum was exchanged to commemorate treaties, marriages, and grand occasions. The beads were often tied together in intricate belts that created pictures, told stories, and basically acted as a memory aid in the oral tradition. It was not until contact with the Europeans that the beads actually became currency unto themselves. Some of the colonies strictly monetized the beads and created a specific exchange rate between wampum and Dutch stuivers, or Spanish reales. Eventually, Dutch colonists started more industrial manufacture of the beads and wound up demolishing the market with overproduction.