Yuval Noah Harari opens Sapiens by asking why Homo sapiens, one of several human species that once existed simultaneously, came to dominate the planet while others went extinct. His answer centers on what he calls the Cognitive Revolution — roughly 70,000 years ago, when sapiens developed a uniquely flexible capacity for language and abstract thought.

What made this revolution distinct:

• Other species could communicate about concrete things ("there's a lion near the river"), but sapiens developed the unique ability to communicate about things that don't physically exist at all
• This capacity for fiction — shared stories, myths, and abstract concepts — allowed sapiens to cooperate in numbers far beyond what any other species could manage
• Chimpanzees can cooperate in groups of dozens through direct personal relationships; sapiens, through shared belief in common fictions, could cooperate in the thousands or millions

This single capacity, Harari argues, is the foundational explanation for everything that follows in human history — not superior individual intelligence or physical capability, but a unique talent for collective belief in shared, unverifiable stories.