Today is the National Day on Writing, a terrific opportunity to devote some time to writing. And the National Writing Project website is teeming with resources to help you celebrate today. To explore those resources, click here.
Here's a bit from Wikipedia on the history of writing.
True writing, in which the entire 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, and is distinguished from proto-writing in that the latter typically avoids encoding grammatical words and affixes, making it difficult or impossible to confidently reconstruct the exact meaning intended by the writer unless a great deal of context is already known in advance.