The Lost Civilisations of the World

There is a persistent and comforting myth that history is a staircase — that each civilisation stands on the shoulders of the last and the whole arrangement climbs steadily upward. The archaeological record says otherwise. Again and again, complex, literate, technically accomplished societies have risen to remarkable heights and then collapsed so completely that their own descendants forgot they existed. We only found some of them again by accident.

Consider the Indus Valley civilisation, which at its peak around 2500 BC may have supported five million people across what is now Pakistan and north-west India. Its cities, Harappa and Mohenjo-daro among them, had grid-planned streets, covered drains and standardised weights at a time when most of Europe was scratching a living. They had baths, wells and possibly the world's first great sanitation system. Then, over a few centuries, the cities emptied. Their script has never been deciphered. We do not even know what they called themselves.

Or take the Khmer Empire, whose capital at Angkor was, by some estimates, the largest pre-industrial city on earth — a metropolis of perhaps three quarters of a million people when London was a town of fifty thousand. Its engineers built reservoirs and canals on a scale that would tax a modern state. Yet by the fifteenth century the great city was being swallowed by the forest, and European visitors who later stumbled on the ruins refused to believe the local people could have built them.

The Americas are full of such stories. The Maya built observatories, tracked Venus to within a day and developed a sophisticated written language, then abandoned their great southern cities centuries before the Spanish arrived. At Cahokia, near modern St Louis, a Mississippian city of perhaps twenty thousand people — larger than London at the time — raised enormous earthen pyramids around the year 1100, and was deserted within three hundred years. Most Americans have never heard of it.

The most humbling discoveries are the recent ones. Satellite imaging and lidar — laser scanning that strips away vegetation — have revealed that the Amazon was not a pristine wilderness before European contact but a managed landscape supporting millions, with causeways, plazas and enormous geometric earthworks hidden under the trees. Disease arrived before the explorers did, travelling along trade routes, and whole societies collapsed before anyone wrote down their names. The jungle did the rest.

Why do civilisations fall? The causes repeat so consistently they amount to a pattern. Climate shifts — a drought of decades, a monsoon that changes its habits — strain a system built for different weather. Elites respond by demanding more from a shrinking base. Trade networks that supplied resilience become routes for disruption. And complexity itself becomes a cost: the canals, the priesthoods, the granaries all require maintenance that a stressed society can no longer afford. Collapse is rarely a single catastrophe. It is a quiet decision, made in a hundred places, to walk away.

There is a lesson in this that I find genuinely sobering rather than merely interesting. Every one of these societies believed, at its height, that it was permanent. Their monuments were built to last forever, and in a sense they have — but as ruins, not institutions. Permanence is not a state a civilisation achieves. It is a performance it must keep giving, and the moment the audience of farmers, traders and taxpayers stops believing, the stones are just stones.

What survives longest, curiously, is not power but knowledge and habit. Indian Ocean sailors still use star paths the Polynesians perfected. Mediterranean farmers plant crops in patterns older than Rome. The ideas outlast the empires that carried them, travelling on quietly through ordinary people who never knew they were curators. Perhaps that is the real measure of a civilisation — not the height of its temples, but how much of it is still useful a thousand years after the last tax was collected.