Why were shells valuable in Indigenous California exchange systems?

In Indigenous California, shells were highly valued because they functioned as a durable medium of exchange within complex property and exchange systems.1

Because many food sources were perishable, these exchange networks served as a vital banking system. Groups with a surplus of food would trade those items for durable goods like shells. These shells could then be stored and used later to acquire fresh food or other resources, such as obsidian, from inland groups.1

This trade was facilitated by professional traders who traveled long distances, connecting coastal communities—where shells were sourced—with inland regions. Beyond their utility as a currency, shells held significant cultural value for many groups, including the Karok and Yurok peoples of Northern California.12