European explorers could read and write, which gave them a clear advantage over the mostly illiterate societies they conquered. Literacy allowed for maps, written sailing directions, detailed study of accounts by previous explorers, and so on. Diamond next discusses why Europeans had writing when the people of most other cultures did not, and he describes the origins of writing.

There are three basic strategies for representing language in written symbols: alphabetic, logographic, and syllabic. Alphabetic systems display individual sounds as written signs. Logographic systems display words as signs. Syllabic systems display syllables as signs. Today, virtually all developed writing systems use a combination of these techniques.

Like food production, writing was invented more than once. Archaeologists believe it was invented independently in Sumeria around 3000 BCE and in Mexico around 600 BCE. Both of these writing systems came into existence slowly as people began using symbols to represent a few words. The systems then developed over thousands of years into complicated mixtures of logographic, syllabic, and alphabetic symbols. These systems were difficult to use, and only a few educated scribes had the skills to use them.

Most other writing systems were created when the principles of writing spread from these original sources. This often happened through a process Diamond calls blueprint copying, by which scribes learned one written system in detail and later adapted it to work with another language. When they did this, they often introduced improvements to the systems. The first true alphabet seems to have occurred in Egyptian hieroglyphics, which developed a set of symbols for the twenty-four consonant sounds in the Egyptian language. However, Egyptians did not use this alphabet to represent all their words. They retained logograms and symbols for many important ideas. Around 1700 BCE, Semites who knew the Egyptian system adopted it and abandoned most logograms, instead using a purely alphabetic system to write the Semitic language. After a few further improvements, the Semitic alphabet was copied by many other cultures. It evolved into today’s major alphabets of Europe, Africa, India, and parts of Asia.

Writing did not always spread through blueprint copying; sometimes it spread through a process Diamond calls idea diffusion. Idea diffusion happened when someone learned the general idea of written language without ever learning the details but adapted the basic principle to a new language. In 1820, a Cherokee man named Sequoyah saw white people using writing and recognized how useful it would be. Later he decided to invent a writing system for the Cherokee language. After trying and giving up on some logographic systems, he figured out that he could use symbols to stand for sounds. He created a system of eighty-five symbols, each of which stood for one syllable of Cherokee speech. Sequoyah’s system was well adapted to Cherokee sounds and easy to learn. Soon after he invented it, Cherokees developed a literacy rate of almost one hundred percent. Sequoyah’s syllabary is one of the best documented examples of idea diffusion in the spread of writing systems, but similar stories probably account for the writing systems of Korea, Easter Island, and several other places.

Having explained how writing was invented, Diamond returns to his question about why it developed in some places rather than others. First, he points out that early writing systems were difficult to learn and limited in their ability to express ideas. Only scribes learned to read and write, and the uses of writing were limited to accounting, political propaganda, official records, astronomical observations, and the like for thousands of years. Poetry developed as an oral tradition; bards like Homer were probably illiterate people who performed primarily for illiterate listeners.

Early writing served the needs of politicians and wealthy landowners. It never developed among hunter-gatherers because they had neither the need nor the means to support full-time scribes. Only when people were producing food and developing politically complex societies did they begin to feel a pressure to use writing. After that, it took many thousands of years for writing to evolve into a system that had widespread usefulness.