A late 19th Century chart illustrating various types of historic writing. Writing was thought to have been invented in a single civilization, a theory named "monogenesis"and originated in ancient Sumer (in Mesopotamia) and spread over the world from there via a process of cultural diffusion. According to this theory, the concept of representing language by written marks, though not necessarily the specifics of how such a system worked, was passed on by traders or merchants traveling between geographical regions