The Tree of Knowledge

Sapiens did not come to dominate the planet because its muscles were stronger or its tools were sharper than those of rival species — Neanderthals, for instance, were probably physically tougher. The real advantage, Harari argues, was cognitive: a mind that emerged roughly seventy thousand years ago, in what he calls the Cognitive Revolution, capable of juggling far more social relationships than any other primate and, more importantly, capable of holding entirely invented, shared fictions in common with strangers. The physical world stayed exactly as physical as it had always been, but social reality suddenly became negotiable in a way it never had been before.

Language, in this account, became something far more powerful than a set of warning cries about predators nearby. It began carrying gossip, tracking reputation, and managing the subtle, shifting politics of a small group — who could be trusted, who had cheated whom, who was sleeping with whom. Anthropologist Robin Dunbar's research on primate group size is one of the threads Harari weaves in here: gossip-capable language let human groups stay socially coherent at sizes well beyond what grooming-based bonding among other primates could support.

Even more strangely, and far more consequentially, human language also began carrying stories about things that don't physically exist at all and that no one could ever touch: guardian spirits, clan identities, abstract rules of conduct, and imagined debts owed between people who had never met. No chimpanzee troop, however socially sophisticated, has ever organized around a myth.

Once a large group of people can genuinely believe in the same invented order, Harari's central claim is that it can cooperate at a scale far beyond anything kinship alone makes possible. Hundreds of people, then thousands, then eventually millions, can act as if they are one coordinated body, purely because they trust the same shared story — a nation, a religion, a currency. This is the hinge on which the rest of human history turns: a real lion fears only teeth and claws, but a human being will fear laws, gods, and flags that have no physical existence whatsoever, and will willingly die defending them.