In the history of how writing systems have evolved in different human civilizations, more complete writing systems were preceded by proto-writing, systems of ideographic or early mnemonic symbols. True writing, in which the content of a linguistic utterance is encoded so that another reader can reconstruct, with a fair degree of accuracy, the exact utterance written down, is a later development. It is distinguished from proto-writing, which typically avoids encoding grammatical words and affixes, making it more difficult or impossible to reconstruct the exact meaning intended by the writer unless a great deal of context is already known in advance. One of the earliest forms of written expression is cuneiform.
Writing numbers for the purpose of record keeping began long before the writing of language. See History of writing ancient numbers for how the writing of numbers began.
It is generally agreed that true writing of language (not only numbers) was independently conceived and developed in at least two ancient civilizations and possibly more. The two places where it is most certain that the concept of writing was both conceived and developed independently are in ancient Sumer (in Mesopotamia), around 3100 BC, and in Mesoamerica by 300 BC, because no precursors have been found to either of these in their respective regions. Several Mesoamerican scripts are known, the oldest being from the Olmec or Zapotec of Mexico.
Independent writing systems also arose in Egypt around 3100 BC and in China around 1200 BC in Shang dynasty (商朝), but historians debate whether these writing systems were developed completely independently of Sumerian writing or whether either or both were inspired by Sumerian writing via a process of cultural diffusion. That is, it is possible that the concept of representing language by using writing, though not necessarily the specifics of how such a system worked, was passed on by traders or merchants traveling between the two regions.
Ancient Chinese characters are considered by many to be an independent invention because there is no evidence of contact between ancient China and the literate civilizations of the Near East, and because of the distinct differences between the Mesopotamian and Chinese approaches to logography and phonetic representation. Egyptian script is dissimilar from Mesopotamian cuneiform, but similarities in concepts and in earliest attestation suggest that the idea of writing may have come to Egypt from Mesopotamia. In 1999, Archaeology Magazine reported that the earliest Egyptian glyphs date back to 3400 BC, which "challenge the commonly held belief that early logographs, pictographic symbols representing a specific place, object, or quantity, first evolved into more complex phonetic symbols in Mesopotamia."
Similar debate surrounds the Indus script of the Bronze Age Indus Valley civilization in Ancient India (2600 BC). In addition, the script is still undeciphered, and there is debate about whether the script is true writing at all or, instead, some kind of proto-writing or nonlinguistic sign system.
An additional possibility is the undeciphered Rongorongo script of Easter Island. It is debated whether this is true writing and, if it is, whether it is another case of cultural diffusion of writing. The oldest example is from 1851, 139 years after their first contact with Europeans. One explanation is that the script was inspired by Spain's written annexation proclamation in 1770.