How humankind conquered the world

Yuval Noah Harari’s “Sapiens,” the most recent crack at what Mr. Christian calls Big History, has already been translated into more than 20 languages and been presented, via online courses, to thousands of mind-blown students. (It was originally written in Hebrew; Mr. Harari, who teaches at the Hebrew University of Jerusalem, did the very idiomatic translation.) Children often still learn history as a tedious parade of names and dates. “Sapiens” is the antimatter version of this kind of history, all sparkling conceptual schemas and ironic apothegms, with hardly a Henry or Louis or Philip in view.

The book’s title is Mr. Harari’s reminder that, long ago, the world held half a dozen species of human, of which only Homo sapiens—thee and me—today survives. The trajectory of our species, Mr. Harari says, can be traced as a succession of three revolutions: the cognitive revolution (when we got smart), the agricultural revolution (when we got nature to do what we wanted), and the scientific revolution (when we got dangerously powerful). Humanity, Mr. Harari predicts, will see one more epochal event. We will vanish within a few centuries, either because we’ve gained such godlike powers as to become unrecognizable or because we’ve destroyed ourselves through environmental mismanagement.

Homo sapiens came into existence more than 200,000 years ago. The term “cognitive revolution” reflects the belief, held by many anthropologists, that for most of that time the species was just a group of insignificant foraging bands wandering about east Africa. Then, Mr. Harari says, “beginning about 70,000 years ago, Homo sapiens started doing very special things.” In this “Great Leap Forward,” as Jared Diamond has called it, our ancestors suddenly overcame their inertia and moved out of Africa, meanwhile inventing boats, battle axes and beautiful art. What happened? Mr. Harari suggests that a yet-undiscovered “Tree of Knowledge mutation” altered the “inner wiring” of our brains, allowing us “to communicate using an altogether new type of language,” one that allowed humans to cooperate in groups. Mutation in place, humankind exploded across the planet.