CLAY TABLET WRITING. “The impressed token shape signs for the large and small measure of wheat came to represent the numerals 10 and 1 respectively. The second class of signs, etched signs representing the commodities and hence represented words. The Sumerians quickly realized that they could represent spoken words other than agricultural commodities with etched signs and so writing emerged to represent spoken language and also abstract numbers.”
https://link.springer.com/chapter/10.1007/978-3-030-59177-9_13