That the history of our species came in stages was an idea that came in stages. Aristotle saw the formation of political entities as a tripartite process: first we had families; next we had the villages into which they banded; and finally, in the coalescence of those villages, we got a governed society, the polis. Natural law theorists later offered fable-like notions of how politics arose from the state of nature, culminating in Thomas Hobbes’s mid-seventeenth-century account of how the sovereign rescued prepolitical man from a ceaseless war of all against all.
But it was Jean-Jacques Rousseau, a hundred years later, who popularized the idea that we could peer at our prehistory and discern developmental stages marked by shifts in technology and social arrangements. In his Discourse on the Origin and the Foundation of Inequality (1755), humans went from being solitary brutes to companionable, egalitarian hunter-gatherers; but with the rise of metallurgy and agriculture, things had taken a dire turn: people were civilized, and humanity was ruined. Once you found yourself cultivating a piece of land, ownership emerged: the field you toiled over was yours. Private property led to capital accumulation, disparities of wealth, violence, subjugation, slavery. In short order, political societies “multiplied and spread over the face of the earth,” Rousseau wrote, “till hardly a corner of the world was left in which a man could escape the yoke.”
Even people who rejected his politics were captivated by his origin story. In the nineteenth century, greater empirical rigor was brought to the conjectural history that Rousseau had unfolded. A Danish archaeologist partitioned prehistory into the Stone, Bronze, and Iron Ages; a British one split the Stone Age into the Paleolithic and the Neolithic. For the emerging discipline of anthropology, the crucial stages were set out in Ancient Society (1877) by the American ethnologist Lewis Henry Morgan. Human beings, he concluded, had emerged from a hunter-gatherer phase of “savagery” to a sedentary “barbarian” era of agriculture, marked by the domestication of cereal grains and livestock. Technologies of agriculture advanced, writing arose, governed towns and cities coalesced, and civilization established itself. Morgan’s model of social evolution, presaged by Rousseau, became the common understanding of how political society came about.