Writing things down so the information can be passed on is a fairly recent human invention. While the Lascaux cave paintings were likely an attempt to graphically capture the realities of a hunt (the first literal hard copy?), they had an artistic element as well as retaining and passing on some knowledge of how to hunt.
The first true books were developed more-or-less concurrently in the Middle East and in East Asia around the 3rd or 4th century BCE using clay tablets, bone, shells, and wood. The first known documents were legal contracts and lists of assets such as bills of lading for ship cargos [1].
While, several forms of paper came to be used for writing as early as the 1st century BCE, it was not until the invention of the printing press and the moveable-type book in the 15th century CE that reading and writing became common. Prior to these inventions there was little incentive for people to learn to read since there were very few books available to be read. Equally, there was little reason for someone to learn to write, since there were few people who could read what might be written.
Books, when they finally arrived on the scene in bulk, provided a knowledge storage and transport medium that transcended the limitations of knowledge-in-brains. Whereas, in earlier eras, if a town in France wanted to build a cathedral and the most knowledgeable mason with that skill happened to live in England, that person would have to physically travel to France. Once books were available, a text on building processes could be sent to France. Even more importantly, the knowledge gained in one generation could be passed with high accuracy to the next. No longer would each generation have to carry the knowledge from the previous generation, remember it, and pass it on to the next. This revolution in knowledge storage triggered an explosion of knowledge acquisition across the globe [2] and through the centuries.
Books became the primary repository of the knowledge of the human race [3].
Knowledge-in-hardware made a strong comeback during the Industrial Revolution when the knowledge of how to make things was incorporated into machines. With this, the manufacture of goods no longer required the constant attention of people with the knowledge-in-brains needed to construct the artifact. But this revolution would not have happened without the knowledge-in-books revolution first. Knowledge-in-books, complementing knowledge-in-brains, became the primary media for retaining everything that humans had learned. Until recently...
FOOTNOTES
[1] Which means the first human beings to write books were lawyers and accountants. Yikes.
[2] Within 60 years of Johannes Gutenberg inventing the printing press, over 20 million volumes were printed in Europe. After on hundred years it was around 200 million.
[3] What about pictures, movies, videos? Aren’t they different from books? Arguably not. The primary difference between books comprising text and books containing still pictures is simply that the language is different. Most alphabetic text does not express an image whereas an image obviously does. Text is largely a symbolic format, though some ideogrammatic languages such as Chinese do have pictorial elements—they are simplified pictures of the things they represent. The Chinese character for “man” (rén: 人) looks a bit like a person.
Moving videos are different, of course, since they have both higher knowledge density, active movement, and temporal sequencing. However, text, still pictures, and videos share the characteristic that they all require a person to view them in order to convey the knowledge in them. Accordingly, I consider them all to be just different variants of books.