The history of the world, by convention, is human history, from the first appearance of Homo sapiens to the present. Human history is marked both by a gradual accretion of discoveries and inventions, as well as by quantum leaps — paradigm shifts, and revolutions — that comprise epochs in the material and spiritual evolution of humankind.
Human history, as opposed to prehistory, has in the past been said to begin with the invention, independently at several sites on Earth, of writing, which created the infrastructure for lasting, accurately transmitted memories and thus for the diffusion and growth of knowledge. Writing, in its turn, had been made necessary in the wake of the Agricultural Revolution, which had given rise to civilization, i.e., to permanent settled communities, which fostered a growing diversity of trades.
Such scattered habitations, centered about life-sustaining bodies of water — rivers and lakes — coalesced over time into ever larger units, in parallel with the evolution of ever more efficient means of transport. These processes of coalescence, spurred by rivalries and conflicts between adjacent communities, gave rise over millennia to ever larger states, and then to superstates or empires. In Europe, the fall of the Western Roman Empire (476 CE) is commonly taken as signaling the end of antiquity and the beginning of the Middle Ages.
A thousand years later, in the mid-15th century, Johannes Gutenberg's invention of modern printing, employing movable type, revolutionized communication, helping end the Middle Ages and usher in modern times, the European Renaissance and the Scientific Revolution.
By the 18th century, the accumulation of knowledge and technology, especially in Europe, had reached a critical mass that sparked into existence the Industrial Revolution. Over the quarter-millennium since, the growth of knowledge, technology, commerce, and — concomitantly with these — the potential destructiveness of war has accelerated geometrically, creating the opportunities and perils that now confront the human communities that together inhabit the planet.
