The invention of writing was a gradual process. Scholars have identified several stages, not only in the evolution of writing systems but also in the diffusion of literacy (the ability to read and write) to different groups in society. Mnemonic symbols that assist memory evolved into systems of words separated into syllables among early peoples. It happened first among the Sumerians and later the Babylonians and Egyptians as commerce necessitated more abstract symbols that could record different products and individuals. From these word-syllabic systems evolved more complex syllabic systems and ultimately, through the Phoenicians, the alphabetic writing of the Greeks.
Beyond these stages of writing development, the early history of literacy may be divided into periods according to the level at which literacy spread among the population. For some centuries after the introduction of alphabetic writing, literacy was restricted to a small elite and limited to a few functions, chiefly religious, accounting, and sometimes political administration. Historians have called these centuries a time of restricted literacy. As writing gained a foothold in more areas of activity, it prompted more general literacy among the elite. At the same time, the diffusion of writing tended to consolidate and standardize regional language.
Some qualifications to the concept of stages in literacy are necessary. First, not all societies move through all stages. For example, nonliterate societies sometimes adopted alphabetic writing from abroad, skipping the earlier stages. Second, although the stages are generally sequential, their order is sometimes reversed. For example, in Europe the literate population narrowed during the medieval period, and in Greece, between the twelfth and ninth centuries B.C., writing utterly vanished. Third, the stages are not mutually exclusive; they express gradual and overlapping developments.
These early developments took place in the context of mass illiteracy and pervasive oral culture. Oral culture did not decrease in contact with written culture; rather, the written word modified and extended communication networks. Not only has the great majority of Earth's population been illiterate through history, the bulk of communication in literate societies is still oral. Nonetheless, writing is a technology, and it allows new modes of communication, administration, and record keeping, as well as innovations in economic, political, and cultural activities.