World population growth has proceeded in two steeper-than-exponential phases, with an intervening standstill from 1– 400 CE. Our interaction model of population, technology, and Earth’s carrying capacity projects to a peak of 11 billion people by 2100. Yet, our impact on Earth’s biosphere may undo our very existence. Then projections in this book, such as a single world state by 4600 CE, become moot. Over 5000 years, the number of states has fallen and top empire sizes have increased exponentially but also in three phases triggered by breakthroughs in message speed: Runner, Rider and Engineer Empires. This approach can lead to a non-Eurocentric periodization of history, with cut-off dates at 3000 BCE, 600 BCE, 600, 1200, and 1800. Various relationships connect world population and top empire and major city sizes, but they have tended to fail since 1800, as the world becomes a single, rapidly interacting system. A distinction of Talkers, Doers, Regulators, and Followers serves to characterize the internal structure of empires. An initial human self-domestication (slavery) seems to be later followed by self-taming. Lists of world history events put the midpoint of history around 1500 CE.

Authority means the ability to affect others’ behavior without applying direct force. Its traces, noted among chimpanzees, develop among the “talking apes.” Human tribes may develop shamans even earlier than full-time chiefs. The advent of agriculture increased population density, enabling ambitious chiefs to have more sway over villagers than they could over sparse hunters: Land tillers are easy to locate and cannot abandon their fields even when hard pressed. A population density of five persons per square kilometer may be the threshold for state formation. Formation of the first states witnessed ferociousness rare in the present humans – or chimpanzees. Tool making shifted gatherers to hunting, and hunting skills may have selected for the most ferocious genes. Agriculture might have started an opposite process of self-taming that still continues, but meanwhile tribal freewheeling turned into utter regimentation, as if the state were the ruler’s household (oikos) and other people his slaves. This human self-domestication reached its fullest extent when the advent of money allowed humans to be sold and bought.

A graph superimposes the growth–decline curves of major Late Rider Empires, from 1200 to 1800. This was a period of shift from horses to sails. West European feudalism indirectly led to respect for law and a curiosity revolution. Inciting exploration, the latter began to give rise to transoceanic empires, first of all Spanish. But at first, Mongol horsemen seized a record-size area, unsurpassed among land-borne empires. Up to 1750 all truly large empires except Spanish remained land bound: Manchu Qing, Russia, Ottoman, and Mughal. The burgeoning French, Portuguese, and British empires were still modest. Much of the Mongol hold meant sparsely populated superficial tribute area, but by conquering China the Mongol empire also became the world’s most populous. Later on, Ming, Mughal, and Qing shared this eminence. Nomad empires were a phenomenon that rose and ended with the Rider phase. The Inca and Aztec empires retraced from scratch the human self-domestication process that the Old World underwent thirty-five centuries earlier, but they still lacked metals and the wheel.

A graph superimposes the growth–decline curves of major Runner Empires, from 3000 to 600 BCE. The Egyptian Old, Middle,and New Kingdoms dominate this period. Egypt’s sheltered location ensured stability, then suffocation. Mesopotamian states remained small, forming a mutual fighting community, until the brief rise of Akkad and Assyria. The Xia–Shang–Zhou empire took off only after 1500 BCE, and in a surprisingly northern location. It’s as if state formation in the west had begun on the Danube instead of Nile. Egypt came closest to the oikos model (state as the ruler’s household), with 90% of produce flown in and out of state storage. It might have been 83% in Sumerian city-states. This aspect of human self-domestication may have begun to retreat with the Hittite empire, and even Assyria. While the Hyksos surprised Egypt with chariots as early as around 1650 BCE, the Assyrians complemented chariots with cavalry only by 665 BCE. The era of Rider Empires was approaching.