Technology often advances at the margins, where new problems challenge people to adapt old tools or to make new ones. (See also Hybrids (2): combinations and connections)
Rich Text Formats
Sumerian writing systems began with a marginal (i.e. edge-case) use. The high-value activity of record keeping for Sumerian royalty demanded the development of high-powered wealth-management tools. Writing was an incredibly rare and expensive information technology usable only by specialists.
It took a few hundred years to be adapted for other uses.
(Alpha) Beta Testing
The repurposing of pictorial rebus-principle scripts to a simpler yet more abstract phonetic alphabet appears to have happened at a point of meeting between literate Egyptians and illiterate Canaanite people – another social margin – in around 1700BC. The Canaanites got the idea of writing, tweaked it a bit to make it work for them, and ran with it.
This was a huge turning point: the innovation of alphabetic writing spread rapidly across the ancient world, and this moment of innovation is apparently the ancestor of every other alphabetic writing known to history. The letter A of the modern Latin alphabet still contains, in the words of Orly Goldwasser, “the ancient Egyptian hieroglyph of the bull sleeping forever in the letter A.” Most of our other letters also have hieroglyphic roots – see this video for a fascinating exposition.
The invention of spaces between letters was another marginal revolution, occurring in Ireland in the late 600s. The non-Latin-speaking monks of the Celtic church found it hard to learn from solid (un-spaced) blocks of Latin words. They introduced spaces between words to make things a bit easier, taught this new technology to the English, and the innovation spread throughout the medieval world.