Currency

In 2005, Yale researchers taught capuchin monkeys to use metal tokens as currency. The monkeys developed gambling and loss aversion spontaneously. Some males exchanged tokens with females for food.

On Yap island in the Pacific Ocean, giant wheel-shaped stones called "Fei" served as currency. One familys ancestor lost an enormous Fei to a storm while transporting it by canoe, but fellow travelers testified to its existence, so the stone retained its value at the bottom of the sea.