The codex, in turn, was transformed by the invention of printing with movable type in the 1450s.
The fourth great change, electronic communication, took place yesterday, or the day before, depending on how you measure it.
When strung out in this manner, the pace of change seems breathtaking: from writing to the codex, 4,300 years; from the codex to movable type, 1,150 years; from movable type to the Internet, 524 years; from the Internet to search engines, nineteen years; from search engines to Google’s algorithmic relevance ranking, seven years; and who knows what is just around the corner or coming out the pipeline?