Most of the world’s largest countries are extremely multicultural. China is a great exception. The vast majority of Chinese people speak Mandarin or a similar language, and most Chinese families have considered themselves Chinese for millennia. Diamond theorizes that China was once as linguistically and culturally diverse as Russia or Brazil but that China began its process of unification far earlier.

To support this point, Diamond turns first to Chinese languages. Mandarin and its seven close relatives, all Sino-Tibetan languages, are collectively spoken by 1.1 billion Chinese people. These languages exist alongside 130 other languages, each of which is spoken by a much smaller population. China’s languages fall into four families. The Sino-Tibetan languages are spoken by the majority of the people throughout the country, whereas isolated islands of people speak the other four families of languages. Most of these languages are related to languages spoken in a variety of Southeast Asian countries. Diamond believes that the speakers of these languages were the original inhabitants of what is now South China. He thinks northern Chinese speakers of Sino-Tibetan languages conquered their neighbors to the south, either adopting them into Chinese cultures or pushing them into Southeast Asia.

Agriculture began in China at least by 7500 BCE, perhaps earlier. It may have originated in two distinct parts of China, but the archaeological record is uncertain. Early Chinese farmers domesticated wild millet and rice, as well as pigs, dogs, and chickens. Several other plant and animal species came into domestication later. The Chinese invented paper, gunpowder, and other important products. Several of Eurasia’s most important germs may have arisen there as well.

China’s cultures began to merge by around the fourth century BCE. Large north–south distances slowed the spread of crops, but not as much as in Africa or the Americas, where deserts prevented expansion. Most of China’s advancements spread from north to south. China’s three early dynasties also originated in the North.

Diamond believes that China’s head start in food production, and subsequent development of writing and technology, gave the country a major advantage over its neighbors. Southeast Asia was still inhabited by hunter-gatherers until the fourth millennium BCE, but they were probably replaced by food producers from South China who fled a North Chinese invasion of their territory. Those early hunter-gatherers seem to have been completely wiped out, leaving few examples of their language or culture. Korea and Japan were also influenced by China, but they were geographically isolated, so they maintained their own languages and identities.