Scientists have discovered the world’s “very first data storage system” — 5,500-year-old clay balls unearthed in Iran that were used for record-keeping in Mesopotamia.

The clay balls, excavated in the 1960s, were made about 200 years before writing was invented. The balls were sealed and scans revealed that they contain tokens in a variety of geometric shapes, varying from golf ball-size to baseball-size.

The interpretation that they were for data storage is based on a 3,300-year-old clay ball found at a site named Nuzi that had 49 pebbles and a cuneiform text containing a contract for a shepherd to care for 49 sheep and goats.