Many are claiming this is a precursor to Bitcoin and distributed ledger technology.
Yap is an island in western Micronesia. Several hundred years ago they developed stone money. This was a monetary system that has many parallels to cryptocurrency.
The stones were quarried a few hundred miles away on the island of Palau. They were brought to Yap and used as currency. The only problem was these stones were up to 13 feet in size. In other words, they were the weight of a car.
These were called Rai. Upon returning to the village, everyone took ownership of the stones with each having individual units. These could be transferred to other members of the community. This was done through the use of a ledger, which everyone kept. If there was a transfer in ownership of the stone, it was broadcast (by word of month) throughout the village. This alerted everyone of the need to update the ledger.
The original Rai was never moved. It remained in the same location. No matter who owned it, the stone was on display for all to see. The value that community assigned to it was transferred through the local economy yet the stone never moved.
Yap islanders devised a public system for tracking and exchanging currency. Even though it was done orally, it was a money transfer system. It was also the basis for their economy.
Hence how many see the correlation between this system and cryptocurrencies of today. Of course, there are detractors to this story. Some economists believe that because the Rai couldn't be divided into small parts that it doesn't fit as currency. However, that is still looking at currency as something physical.
Regardless of the debate, it is interesting to see the idea of distributed ledger technology and a decentralized non-bank money system predate Bitcoin by a few hundred years.