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Out of Africa

Every person alive today, from Lagos to Lima to Lahore, shares a family tree whose deepest roots lie in Africa. Homo sapiens evolved there: the oldest fossils assigned to our lineage, found at Jebel Irhoud in Morocco, are roughly 300,000 years old, and for most of our history Africa was the only home our species knew. It was a crowded neighbourhood by later standards, shared with other kinds of human, and our ancestors spread across the whole continent long before they left it.

Small groups did probe beyond Africa earlier, and fossils from caves in Israel hint at forays more than 100,000 years ago. Most of those pioneers seem to have left little genetic trace. The dispersal that counts, the one written into the DNA of everyone with roots outside Africa, came later, roughly 70,000 to 50,000 years ago. Bands crossed into Arabia and the Levant, probably during wetter spells when deserts briefly turned to grassland. There they met Neanderthals, and not only as rivals.

Did you know? Most people with ancestry outside Africa carry around 1 to 2 per cent Neanderthal DNA, a genetic souvenir of encounters soon after the exit.

From the Near East the expansion ran in several directions at once. One stream hugged the coasts of southern Asia, living off shellfish and fish, and then did something remarkable: it crossed open sea. Even at the lowest sea levels of the Ice Age, reaching Sahul, the joined landmass of Australia and New Guinea, meant paddling or sailing out of sight of land. People were there by at least 50,000 years ago, and possibly earlier; the oldest dates are still argued over. Other groups pushed into Europe by about 45,000 years ago, where they lived alongside Neanderthals for several thousand years before the older species disappeared, and onto the frozen steppes of Siberia.

The Americas came later. During the Ice Age a land bridge called Beringia joined Siberia to Alaska, and people crossed it, or travelled along its coast by boat. Most scholars accept that humans were in the Americas by around 16,000 years ago; footprints at White Sands in New Mexico suggest more than 20,000 years, though that claim is debated. Within a few thousand years people had reached the tip of South America. The last great empty lands were the remote islands of the Pacific, settled by Polynesian voyagers within the last 3,000 years; Aotearoa New Zealand, reached around 1250 CE, was among the very last.

This was not a march with a destination. It was the slow drift of foragers following game, coastlines and fresh water, each generation moving perhaps only a few kilometres beyond the last. Yet the result was extraordinary: a single species, with one African origin, occupied every continent except Antarctica. Because the migrants were few, people outside Africa carry only a slice of the genetic variety found within it, and Africa still holds the greatest share of human genetic diversity. Everything that follows begins with a walk.

The Cognitive Spark

Somewhere along the road out of Africa, the archaeological record changes character. Alongside stone tools, sites begin to yield things with no obvious practical use: pierced shells strung as beads, lumps of red ochre scratched with patterns, and later carved figurines, flutes and painted walls. These are traces of symbolic thought, the ability to let one thing stand for another. The historian Yuval Noah Harari popularised the phrase Cognitive Revolution for this shift, dating it to around 70,000 years ago.

The evidence is real; whether it amounted to a sudden revolution is another matter. At Blombos Cave, on South Africa's southern coast, someone drew a crosshatched pattern with an ochre crayon on a stone flake around 73,000 years ago, the oldest known drawing. Shell beads from Blombos and from Taforalt in Morocco are older still, about 75,000 and 82,000 years. Many archaeologists therefore see symbolic behaviour building up gradually in Africa over tens of thousands of years, flickering on and off as populations rose and fell, rather than switching on at a single moment.

What matters is what symbols made possible. A chimpanzee troop can coordinate only among animals that know one another personally, and human groups bound purely by personal ties seem to top out at around 150 people, a figure associated with the anthropologist Robin Dunbar. Language changed that. It could carry gossip about who was trustworthy, and it could describe things that do not exist at all: spirits, ancestors, a clan's totem animal. Belief in such shared fictions lets people who have never met behave as members of the same group, trade with one another and turn up for the same rituals.

Did you know? The Lion-man of Hohlenstein-Stadel in Germany, carved from mammoth ivory about 40,000 years ago, is one of the oldest known figurative sculptures, and it shows a creature that never existed.

By 40,000 years ago the evidence is unmistakable and global. A painting in Leang Karampuang cave on the Indonesian island of Sulawesi, showing a wild pig with human-like figures, has been dated to at least 51,000 years ago. In the caves of southern Germany people played flutes made from bird bone and mammoth ivory. Ornaments and fine stone travelled hundreds of kilometres from their sources, signs of exchange between groups who were not kin.

This is the deep root of everything that follows. Money, laws, gods, nations and companies are all, in Harari's sense, shared fictions: they exist because enough people agree to act as if they do. That does not make them unreal; a banknote buys bread precisely because everyone believes it will. The capacity to imagine together gave Homo sapiens a decisive advantage in scale. And scale, again and again, is what history rewards.

Fire and the Brain

Every human society on record cooks. No other animal does. The primatologist Richard Wrangham argues that this is no coincidence: in his cooking hypothesis, set out in the book Catching Fire (2009), mastering fire was not just a handy trick but a force that reshaped our bodies.

The logic runs like a chain. Heat breaks down tough fibres, gelatinises starch and denatures protein, so cooked food is softer and yields more usable energy than the same food eaten raw; feeding experiments with animals support the point. Cooking also kills many parasites and bacteria and neutralises some plant toxins, widening the menu. Less effort spent chewing and digesting means energy freed for other uses. One study estimated that modern humans spend under 5 per cent of their daily activity feeding, while a primate of our size would be expected to spend nearly half.

The brain is where much of that energy went. It makes up about 2 per cent of an adult's body weight but burns roughly 20 per cent of its resting energy, an extravagant organ to run. The expensive tissue hypothesis, put forward by Leslie Aiello and Peter Wheeler in 1995, noted that the human gut is unusually small for a primate of our size; a shorter gut may have helped pay for a bigger brain. Brain size certainly grew. Australopithecines, some three million years ago, had brains of around 450 cubic centimetres, little more than a chimpanzee's. Homo erectus, appearing around 1.9 million years ago, averaged closer to 900, and modern humans average about 1,350.

Did you know? Burnt bone and plant ash in Wonderwerk Cave, South Africa, show that early humans were using fire about one million years ago.

The weak link is the dating. Wrangham ties cooking to the rise of Homo erectus, with its smaller teeth and jaws, but firm evidence of controlled fire is much younger. Wonderwerk Cave offers traces from around a million years ago; Gesher Benot Ya'aqov in Israel shows repeated burning about 780,000 years ago; and regular, habitual fire use appears widespread only after about 400,000 years ago, at sites such as Qesem Cave. Either cooking began earlier than the surviving ash can show, or brains first grew for other reasons, such as more meat and better tools, with fire speeding the trend later. The debate is very much alive.

Fire did more than cook. It kept predators at bay, extended the day past sunset and let people move into colder lands. The evening hearth also became a social space; anthropologists who have listened to firelit talk among Kalahari foragers find that it turns from daytime business to stories. By outsourcing part of digestion to the flame, our ancestors bought themselves time, energy and company. Few bargains in evolution have paid so well.

The First Artists

In December 1994 three cavers, Jean-Marie Chauvet, Éliette Brunel and Christian Hillaire, squeezed into a sealed chamber above the Ardèche gorge in southern France and found walls crowded with lions, rhinoceroses, horses and mammoths. Radiocarbon dating placed the oldest paintings of Chauvet Cave at around 36,000 years old. The artists used the bulges of the rock to give animals volume, drew some with extra legs as if in motion, and scraped the walls clean before painting. Nothing about them looks primitive.

Chauvet is famous, but it is neither alone nor the oldest. Lascaux, in the Dordogne, discovered by four teenagers in September 1940, is younger, at around 17,000 years, and holds some 600 painted figures and about 1,500 engravings. In Spain, Altamira's ceiling of bison was dismissed as a forgery for two decades after its discovery in 1879; experts could not believe Ice Age foragers had made it. Further east the record is older still. Cave paintings on the Indonesian island of Sulawesi date back at least 45,000 years, and one scene there, a wild pig with human-like figures, to at least 51,000. In Australia's Kimberley region, a kangaroo painted on a rock-shelter ceiling has been dated to about 17,300 years ago, using mud wasp nests built over the paint.

Did you know? Lascaux was closed to the public in 1963 because the breath and body heat of visitors were damaging the paintings; tourists today visit faithful replicas.

The materials were simple: red and yellow ochre, charcoal and manganese oxide, applied with fingers, pads of moss or fur, or blown through hollow bones. Hand stencils, made by spraying pigment around a hand pressed to the rock, appear from Spain to Sulawesi to the Cueva de las Manos in Argentina, one of humanity's most widespread signatures.

What the paintings were for is harder to say, and honest scholars admit it. The French priest and prehistorian Henri Breuil proposed hunting magic: depicting an animal to gain power over it. Yet the animals painted are often not the ones people ate most; at Lascaux the reindeer that fed the artists barely appear on the walls. Others, notably David Lewis-Williams, argue for shamanism and altered states, pointing to geometric signs and half-human figures. Some images may have been teaching aids, records of the seasons, or marks of a group's territory. Many were placed deep underground, reached only by flickering lamplight, which suggests the act of making and viewing mattered as much as what was shown.

Whatever their purpose, these walls prove that the symbolic mind was fully formed among foragers. Long before farming, cities or writing, people stored knowledge and belief outside their own heads, in images others could see long after the makers were gone. Art came before almost everything else.

The Farming Bargain

For around 95 per cent of our species' existence, people lived by foraging: gathering plants, hunting animals and fishing. Then, from about 10,000 BCE, in the hills and valleys of the Fertile Crescent, running from the Levant through southern Turkey to the Zagros mountains of Iran, some communities began to plant and harvest crops deliberately. Over the following millennia farming arose independently in perhaps a dozen places, from China to New Guinea to Mexico.

Why change a way of life that had worked for hundreds of thousands of years? No single answer satisfies. The end of the last Ice Age brought a warmer, wetter and, crucially, more stable climate after about 9700 BCE, making plant harvests more predictable. In the Levant the Natufians had already settled in villages to exploit wild cereals, and a cold snap known as the Younger Dryas may have pushed their successors to cultivate what they had once only gathered. Rising population, and perhaps a wish to brew and feast, may also have played a part. At Göbekli Tepe in southern Turkey, people who still lived mainly by hunting and gathering raised carved stone pillars around 9500 BCE, a hint that ritual gatherings needed food on a new scale.

Did you know? The great pillars of Göbekli Tepe, some over 5 metres tall, were raised by people who had not yet fully adopted farming, overturning the idea that temples came only after agriculture.

The bargain turned out to be harsh for individuals. Skeletons from many early farming communities show shorter stature, more tooth decay from starchy food, signs of anaemia and joints worn by grinding grain and hauling loads. Diets narrowed from hundreds of wild foods to a few staples, so a single failed harvest could mean famine. Living close to animals and to one another's waste brought new infectious diseases. The geographer Jared Diamond called agriculture "the worst mistake in the history of the human race" in a famous 1987 essay; many scholars think that overstates it, but the health penalty is well documented.

Yet farming won, for one decisive reason: numbers. A hectare of wheat feeds far more people than a hectare of wild land. Farmers could also have children closer together, because a settled mother need not carry toddlers on long treks. Farming populations grew, spread and absorbed or displaced foragers wherever soils allowed. Once land was cleared and stores were full, there was rarely a way back.

Settled life brought something else: property. Fields, herds and granaries could be owned and inherited, and differences in wealth could grow from one generation to the next. The farming bargain fed the many and enriched the few. Few who struck it understood the terms.

Domesticating Life

Domestication is not the same as taming. A tamed animal is one individual used to people; a domesticated species has been changed, generation by generation, until its body and behaviour depend on human care. It happened slowly, often without anyone intending it, and it happened again and again in different parts of the world.

The dog came first, descended from wolves that began living alongside Ice Age hunters, probably more than 15,000 years ago; a dog buried with two people at Bonn-Oberkassel in Germany about 14,000 years ago appears to have been nursed through a serious illness. Crops and herd animals followed after the Ice Age. In the Fertile Crescent, einkorn and emmer wheat, barley, lentils and peas were brought under cultivation from about 9500 BCE, and sheep, goats, cattle and pigs were domesticated within the next millennium or so. The key change in wheat was a mutation that stopped ripe ears shattering and scattering their seed. In the wild, plants with that trait die out; under a harvester's sickle they thrive, because people gather and replant exactly those seeds.

Other centres worked independently. In China, millet was cultivated along the Yellow River and rice along the Yangtze, with rice fully domesticated by around 4000 BCE after thousands of years of cultivation. In the highlands of New Guinea, farmers at Kuk Swamp were managing taro and bananas from around 7000 BCE. In Mexico, maize was bred from a scraggly wild grass called teosinte about 9,000 years ago, its cobs growing over millennia from a thumb's length to the size we know. The Andes gave the world potatoes, quinoa, llamas and alpacas; Africa's Sahel gave sorghum and pearl millet by around 3000 to 2500 BCE.

Did you know? The aurochs, the huge wild ancestor of domestic cattle, survived in Europe until 1627, when the last known animal died in the forest of Jaktorów in Poland.

The changes ran both ways. Crops and animals came to depend on people, and people on them. Herds needed pasture and protection; fields needed weeding, watering and guarding. Human genes changed too. Most mammals lose the ability to digest milk after weaning, but among herding peoples in Europe, East Africa and the Middle East, mutations allowing adults to digest lactose spread rapidly over the last few thousand years. Populations with long histories of starchy diets also tend to carry extra copies of the gene for amylase, the enzyme that digests starch.

The domesticates travelled, remaking landscapes far from their homelands. Wheat and cattle spread across Europe and into South Asia; rice moved across Asia; maize spread from Mexico through much of the Americas long before 1492. Of the thousands of plant species humans have eaten, a handful now supply most of our calories, with wheat, rice and maize alone providing around half. The partnership struck in a few valleys still feeds the world.

The First Towns

The first towns grew from farming villages that simply kept growing. Two sites dominate the story. Jericho, beside a perennial spring in the Jordan Valley, was occupied from around 9600 BCE. When the archaeologist Kathleen Kenyon dug there in the 1950s, she found a stone wall and a great round tower about 8.5 metres high, built around 8000 BCE, with an internal staircase of 22 steps. Its purpose is still argued over: defence against raiders, protection from floods, or a monument that bound the community together. Later inhabitants buried their dead beneath their houses and modelled faces in plaster over some of their skulls, keeping the ancestors close.

The second site is stranger. Çatalhöyük, on the Konya plain of central Anatolia in modern Turkey, flourished from about 7100 to 5950 BCE and at its height housed perhaps 3,500 to 8,000 people; estimates vary. It had no streets. Mud-brick houses were built wall to wall, so residents walked across the flat rooftops and climbed down into their homes by ladder, through an opening that also let out smoke from the oven. Rooftops served as the town's lanes, workshops and meeting places.

Inside, houses followed a remarkably standard plan: a main room with hearth and oven, raised platforms for sleeping and working, and side rooms for storage. The dead were buried beneath the platforms, sometimes dozens in a single house. Walls were plastered and replastered, often painted with hunting scenes, geometric patterns and vultures, and some rooms held the horns of wild bulls set into benches and pillars. When a house grew old it was filled in and a new one built on top, raising the mound over the centuries to some 20 metres.

Did you know? One Çatalhöyük wall painting has been hailed as the world's oldest map, a town plan beneath a twin-peaked volcano, though some archaeologists read it as a leopard skin.

What is missing is as telling as what is there. No palace, no temple district and no grand tomb has been found. The excavator James Mellaart, who dug there in the 1960s, thought certain richly decorated rooms were shrines; the later team led by Ian Hodder, working from 1993, concluded that ritual happened in ordinary homes. Houses, diets and burials look broadly similar, suggesting a society that was, for its size, notably equal. What held it together seems to have been shared routines, ancestors and ritual, rather than the command of a ruler.

Elsewhere, similar experiments were under way: Mehrgarh in Pakistan and Jiahu in China, each with its own crops and customs. These early towns show that humans could live densely and peacefully for centuries without kings. Hierarchy was not a law of nature. It arrived later, with surplus, and it had to be built.

The Surplus Trap

Farming produced, in good years, more food than farmers needed. That surplus changed the shape of society. A family could feed itself from its fields; a village could feed a potter, a priest or a full-time warrior. By the fourth millennium BCE, on the floodplains of southern Mesopotamia, surplus was feeding whole classes of people who never touched a plough.

Not every crop was equally useful for this. The political scientist James C. Scott, in Against the Grain (2017), points out that the earliest states were built on cereals: wheat and barley in Mesopotamia and Egypt, millet and rice in China, maize in Mesoamerica. Grain ripens all at once, above ground and in plain view, so a tax collector can see the harvest and estimate it. It can be measured by volume, carried, and stored for years. Root crops such as cassava can be left in the ground and dug up as needed, while fruit and fish rot. Grain, in short, is visible, storable and taxable.

Around the city of Uruk, which by about 3200 BCE may have held 25,000 to 50,000 people (estimates vary), temple officials gathered barley into great storehouses and paid it out as rations. Archaeologists find vast numbers of crude, mass-produced bevelled-rim bowls at sites of this period, and many think they were used to measure out daily grain rations for workers.

Did you know? The early cuneiform sign for "bread" or "ration" seems to depict one of these bowls, and the sign for "to eat" combines it with a human head.

Surplus needed managers. Scribes recorded who owed what. Priests presented the gathering and sharing out of grain as the will of the gods, who in theory owned the land. Soldiers protected the stores and enforced collection, and leaders sat at the top: first temple administrators, later kings, called in Sumerian lugal, literally "big man". Egypt followed a similar pattern, as officials measured the height of the Nile's flood partly to predict the harvest and set taxes. Compulsory labour, raised in the farming off-season, built canals, walls and, in time, pyramids.

Scott and others stress the darker side. Early states needed people more than land, and they captured, conscripted and enslaved them; walls kept enemies out but also kept farmers in. Crowded, grain-fed populations suffered epidemics, and early states were fragile, often collapsing back into villages. Many people fled to the hills or the steppe when the demands grew too heavy.

This is the surplus trap: the more a society stored, the more it needed someone to guard, count and command the store, and the harder it became to live outside the system. The granary was where power began.

Marks Become Words

Writing was not invented to record stories. It was invented to keep accounts. From about 8000 BCE, villages across the Near East used small clay tokens, shaped as cones, spheres, discs and cylinders, apparently to stand for quantities of goods: a measure of grain, a sheep, a jar of oil. The archaeologist Denise Schmandt-Besserat argued in the 1970s and 1980s that these tokens were the direct ancestors of writing, and while details of her theory are debated, the broad sequence is widely accepted.

The decisive steps came in southern Mesopotamia in the fourth millennium BCE. To make a record tamper-proof, tokens were sealed inside hollow clay balls, called bullae, around 3500 BCE. Because the contents could not be checked without breaking the envelope, people pressed the tokens into its surface before sealing it. Soon someone realised the impressions alone were enough, and the ball flattened into a tablet. By about 3300 BCE accountants at Uruk were pressing number signs into tablets, and by about 3200 BCE they were adding drawn signs for the things being counted: barley, sheep, beer, workers.

These early tablets, called proto-cuneiform, are overwhelmingly administrative, recording goods, rations and labour, and most of the rest are word lists used to train scribes. One Uruk tablet records a quantity of barley over 37 months and bears the signs Ku-shim, which may be the name of an official, possibly one of the oldest recorded personal names.

Did you know? Cuneiform was used for more than 3,000 years; the last datable tablet, an astronomical record from Babylonia, was written around 75 CE.

The leap from counting to language came with the rebus principle: using a sign for its sound rather than its meaning, as an English speaker might draw a bee and a leaf to write "belief". Once signs could stand for syllables, scribes could write names, grammar and eventually anything that could be said. Pressed into wet clay with a cut reed, the signs became the wedge-shaped strokes that give cuneiform its name, from the Latin cuneus, wedge. Over the centuries the script served Sumerian, then Akkadian, Hittite and other languages. Around 2300 BCE Enheduanna, high priestess of the moon god at Ur and daughter of Sargon of Akkad, composed hymns under her own name, making her the first named author in history. Poems about Gilgamesh followed, and law collections such as Hammurabi's, around 1754 BCE.

Mesopotamia was not alone. Writing appeared in Egypt at around the same time, and was invented independently in China by about 1200 BCE, where it survives on Shang dynasty oracle bones, and in Mesoamerica during the first millennium BCE. Each time, practical needs came first. Writing let memory outlive the person who held it. Its first job was to count sheep.

Settling Changed Us

Step back and the scale of the change is startling. Around 10,000 BCE every human on Earth, perhaps five million people, lived by foraging, in bands that moved with the seasons. By 3000 BCE cities of tens of thousands stood beside the Euphrates, Egypt was being unified under a single king, and scribes were writing. By the start of the Common Era, the world's population had risen to somewhere between about 170 and 300 million; estimates vary widely, but the trend does not. The archaeologist V. Gordon Childe named these changes the Neolithic Revolution and the Urban Revolution.

Did you know? Farming has existed for only about 12,000 years, less than 5 per cent of the roughly 300,000-year history of Homo sapiens.

The word revolution can mislead. The shift took thousands of years and many generations who never noticed it happening. Nor was it a one-way street. The anthropologist David Graeber and the archaeologist David Wengrow, in The Dawn of Everything (2021), stress how many societies experimented: farming a little and foraging a lot, gathering in large seasonal settlements and then dispersing, building monuments such as Göbekli Tepe or, much later, Poverty Point in Louisiana without full-time agriculture. Pastoral nomads on the steppes and in the Sahara built another kind of complex society entirely, mobile but rich in herds. Foraging peoples, from the San of southern Africa to Aboriginal Australians and the peoples of the Pacific Northwest, sustained sophisticated ways of life into modern times.

Still, the settled world had a strong pull. Fields and stores fed more people than wild land could; more people meant more labour, more soldiers and more ideas; and the institutions of settled life, property, taxation, writing, law and organised religion, built on one another. Once a society had grown dense, it could rarely shrink back without famine and collapse.

The costs came bundled with the gains. Settlement brought epidemic disease, hard labour, war over land and deep inequality between rulers and ruled, men and women, free and enslaved. It also brought specialists who could spend their lives on metalwork, astronomy, medicine and poetry. Every later chapter, from the pyramids to the printing press to the microchip, rests on the decision of ordinary people, long ago, to stay put a little longer each year.

Was it humanity's best decision or its costliest? The honest answer is both, and that nobody actually decided. It was the sum of countless small choices to plant one more field or stay one more season. What grew from those choices were the first civilisations, along the Tigris and Euphrates, the Nile, the Indus and the Yellow River. History, in the sense of written records, begins here.

The Land Between Rivers

Southern Mesopotamia does not look like a cradle. It is a flat, baking plain where rain barely falls and stone, timber and metal are almost absent. Yet between the Tigris and the Euphrates, in what is now southern Iraq, the people of Sumer built the world's first true cities, invented writing, set down written law and opened schools. Recorded history, in the literal sense, starts here.

The paradox is the point. The rivers laid down deep, fertile silt, but they flooded in spring, often violently and just as crops ripened, and in summer the land was too dry to farm without water brought to it. Survival meant digging and maintaining canals, storing grain and settling disputes over water. Those jobs needed organisers, and organisers needed records. A gentler landscape asked for less cooperation; this one rewarded it.

By around 3500 BCE, Uruk had become something new: a settlement of many thousands, perhaps 40,000 or more by 2900 BCE on common estimates, with monumental temples, workshops and, later, a great wall that legend credited to its king Gilgamesh. Other city-states followed, Ur, Eridu, Lagash, Kish and Nippur among them, each with its own patron god, its own rulers and fields stretching out along the canals. They traded grain and textiles for timber, copper and stone from Anatolia, Iran and as far as the Indus valley.

Writing grew out of bookkeeping. Temple administrators had long used clay tokens to count goods; around 3300 to 3200 BCE scribes at Uruk began pressing signs into clay tablets to record rations, livestock and labour. Over centuries the signs became cuneiform, wedge-shaped marks made with a cut reed, flexible enough to write Sumerian and later Akkadian, Hittite and many other languages. Training scribes required the edubba, the 'tablet house', where pupils spent years copying word lists, sums and proverbs: the first schools on record. Law followed. The code of Ur-Nammu, king of Ur around 2100 BCE, is the oldest written law code to survive, setting fines in silver for injuries.

Did you know? The 60 minutes in an hour and the 360 degrees in a circle descend from the base-60 counting the Sumerians used and the Babylonians refined.

Sumer itself did not last. Sargon of Akkad conquered its cities around 2330 BCE, a Sumerian revival under the Third Dynasty of Ur collapsed around 2004 BCE, and Babylon later inherited the land. But the toolkit outlived its makers: cities, scribes, law and arithmetic passed to every power in the region and far beyond. On the Nile, Egypt was assembling a parallel experiment at almost the same moment, under a very different river.

The first civilisation was a solution to a difficult river.

The Gift of the Nile

Few countries are as legible from space as Egypt: a thin green ribbon of farmland, often only a few kilometres wide, threaded through the Sahara. The Egyptians called their land Kemet, the 'black land', after the dark silt the river left behind, and the desert around it Deshret, the 'red land'. The Greek historian Herodotus, visiting in the fifth century BCE, passed on the phrase that stuck: Egypt was the gift of the river.

The gift arrived on schedule. Each summer, monsoon rains over the Ethiopian Highlands swelled the Blue Nile and the Atbara, and from around July the water spread across the valley floor, peaking in September. As it drained away in autumn it left a fresh layer of fertile mud, already soaked, ready for sowing. The calendar followed the rhythm in three seasons of four months: Akhet, the inundation; Peret, the growing; Shemu, the harvest.

Compare Mesopotamia. The Tigris and Euphrates flooded in spring, unpredictably, and could wreck crops; Mesopotamian myths imagined gods sending a deluge to destroy humankind. The Nile was gentler and better timed, and Egyptian thought prized ma'at, a cosmic order of balance and justice that the king was bound to uphold. A predictable river encouraged a vision of a predictable universe, with the pharaoh at its hinge.

Order also meant administration. Officials measured each flood with nilometers, stepped gauges cut into the riverbank, and assessed taxes on the expected harvest. A good flood filled the granaries; too low brought famine, too high swept villages away. Surplus grain paid for the state's monuments. Around 3100 BCE, Upper and Lower Egypt were united under one king, traditionally Narmer, and within five centuries Khufu's Great Pyramid at Giza, finished around 2560 BCE, stood about 146 metres tall, the tallest structure on Earth for almost 3,900 years.

Did you know? Cleopatra lived closer in time to the Moon landing than to the building of the Great Pyramid.

The state endured, with interruptions. The Old, Middle and New Kingdoms were separated by 'intermediate periods' of division, drought and foreign rule, and the New Kingdom of Hatshepsut, Akhenaten and Ramesses II pushed Egyptian power deep into Nubia and the Levant. Upriver, the African kingdom of Kush grew strong enough that its kings ruled Egypt as the 25th Dynasty in the eighth and seventh centuries BCE. Independence ended only in 30 BCE, when Cleopatra VII died and Rome annexed the country, roughly 3,000 years after unification. Even then the flood rolled on, feeding Rome's bread supply, until the Aswan High Dam tamed it in the 1960s.

A dependable river made a dependable state.

The Indus Enigma

In the 1920s, archaeologists digging at Harappa in Punjab and Mohenjo-daro in Sindh, both now in Pakistan, realised they had found a civilisation that nobody had known existed. Its cities were as old as those of Sumer and Egypt, and its territory was larger than either: the Indus, or Harappan, civilisation spread across perhaps a million square kilometres of today's Pakistan and north-west India, from Baluchistan to Gujarat and the plains near Delhi.

Its mature phase ran from about 2600 to 1900 BCE, and its most striking feature was planning. Mohenjo-daro, home perhaps to 30,000 or 40,000 people on the usual estimates, had a raised citadel and a lower town laid out along broad streets running north–south and east–west. Houses of fired brick, made to a standard 1:2:4 proportion across hundreds of sites, had wells and bathing areas. Waste water ran into covered brick drains along the streets, with openings for cleaning, a level of urban sanitation few cities matched before the Romans. On the citadel sat the Great Bath, a pool about 12 by 7 metres, sealed with bitumen and reached by steps at either end.

Trade was organised with the same precision. Cubic stone weights followed a single standard from one end of the region to the other. Carved steatite seals, many showing a one-horned animal that excavators nicknamed the 'unicorn', were used to stamp goods. Some turned up in Mesopotamia, whose texts mention a distant land called Meluhha that sent carnelian, timber and ivory by sea; most scholars think Meluhha was the Indus. At Lothal in Gujarat, a large brick basin may have been a dockyard, though that reading is debated.

Did you know? The famous 'Priest-King' statue from Mohenjo-daro got its title from excavators; nobody knows whether he was either.

Then there is the silence. The seals carry short inscriptions in a script of roughly 400 signs, but the average text is only about five signs long and no bilingual key has been found, so it remains undeciphered after a century of attempts. No royal tombs, grand palaces or certain temples have been identified, and there is little sign of warfare. Whether the cities were run by kings, priests, merchants or councils is unknown. It is a civilisation we can see in astonishing detail and cannot hear at all.

Its end is better understood than its beginning. After about 1900 BCE the great cities emptied gradually as people moved east and into smaller villages. The old story of a violent 'Aryan invasion', built on a few skeletons at Mohenjo-daro, has been abandoned by archaeologists. The likely causes were a weakening monsoon, shifting rivers and the drying of the Ghaggar-Hakra system, together with a decline in long-distance trade. The plumbing, at least, outlasted the arguments.

Its drains still speak clearly. Its writing still does not.

The Mandate of Heaven

In China, the founding idea of political legitimacy was announced by the winners of a war. Around 1046 BCE, King Wu of the Zhou, a people from the Wei River valley in the west, defeated the last ruler of the Shang at the Battle of Muye. The Shang had ruled the Yellow River plain for some five centuries, leaving bronze ritual vessels of astonishing skill and the earliest known Chinese writing, on oracle bones used to ask ancestors about harvests, wars and even a king's toothache.

The Zhou needed to explain why their seizure of power was right. Their answer, traditionally credited to King Wu's brother the Duke of Zhou, was Tianming, the Mandate of Heaven. Heaven, Tian, granted the right to rule to a virtuous family, and withdrew it when rulers became cruel, corrupt or negligent. The last Shang king, remembered as a drunken tyrant, had forfeited it; the Zhou had simply received it. That much of this portrait comes from the victors' own records is itself a lesson in how the doctrine worked.

The idea was both steadying and dangerous. It made kingship conditional on conduct, so a ruler had every reason to govern well, keep the granaries full, repair the dykes and perform the rites. But success was also its own proof: a rebel who won had, by definition, gained Heaven's favour, while one who failed was merely a bandit. Floods, famines, earthquakes and comets could be read as signs that the mandate was slipping, giving hungry peasants and ambitious generals a ready-made justification for revolt.

Did you know? The modern Chinese word for revolution, geming, originally meant 'removing the mandate'.

The Zhou themselves illustrate the cycle. After 771 BCE their power fragmented, and the long Spring and Autumn and Warring States periods followed, during which thinkers such as Confucius looked back to the early Zhou as a model of good order. Mencius, in the fourth century BCE, went further, arguing that killing a tyrant who had abandoned virtue was not the murder of a true king at all. The Qin unified China in 221 BCE and collapsed within fifteen years; the Han dynasty that followed was founded by Liu Bang, a minor local official of humble birth, whose victory was taken as proof of Heaven's choice.

Later historians arranged China's past into a dynastic cycle: a new house restores order, prospers, decays, meets disaster and rebellion, and gives way to another holding a fresh mandate. Real history was messier, but the pattern shaped how rulers and rebels understood themselves until the Qing dynasty fell in 1912. It offered something Europe's divine-right kings never had: a respectable way to say that the government had failed.

A throne that could be lost had to be earned every day.

Hammurabi's Code

Around 1754 BCE, near the end of a long reign, Hammurabi of Babylon had his laws carved onto a polished black stone stele about 2.25 metres tall and set up for public view. At the top, a relief shows the king standing before Shamash, the sun god and god of justice. Below, in thousands of lines of cuneiform, run about 282 laws, framed by a prologue and epilogue in which the king declares that he set them down so that the strong should not oppress the weak.

Hammurabi, who ruled from around 1792 to 1750 BCE, had turned Babylon from one city-state among many into the master of Mesopotamia, defeating Larsa, Eshnunna and Mari. A uniform set of rules suited a ruler stitching a kingdom together. His laws were not the first: the code of Ur-Nammu came some three centuries earlier, and that of Lipit-Ishtar of Isin around 1930 BCE. But Hammurabi's is the longest and best preserved, and it covers an extraordinary range: theft, trade, loans, wages, rents, marriage, divorce, inheritance, adoption, surgeons' fees, boat hire and the duties of builders.

Its most famous principle is lex talionis, the law of retaliation. Law 196 says that if a man destroys the eye of another free man, his own eye shall be destroyed. Brutal to modern readers, it was also a limit: one eye for one eye, not a blood feud or a burned village. Yet equality had its boundaries. Penalties depended on rank, across three classes: the awilum, a full free person; the mushkenum, a commoner or dependant; and the wardum, a slave. Destroying a commoner's eye cost one mina of silver, about half a kilogram; a slave's eye, half the slave's price, paid to the owner. A builder whose shoddy house collapsed and killed its owner could be put to death.

Did you know? The stele was carried off as war booty to Susa in Iran around 1158 BCE, where French archaeologists found it in 1901.

How the code was used is still debated. Thousands of contemporary contracts and court records survive, yet they almost never cite it, and many scholars see the stele less as a statute book than as a royal advertisement: a monument proving to gods and subjects that Hammurabi was a just king. Even so, the idea that rules should be fixed, public and written, rather than invented on the day by whoever held power, was a decisive step.

The stele now stands in the Louvre in Paris. Scribes went on copying its laws for over a thousand years, and the eye-for-an-eye formula reappears in the Hebrew Bible. Law had become something a person could point to.

Written rules do not make a society fair, but they make unfairness visible.

The Wheel and Sail

Some of the most important inventions in history have no known inventors. Nobody can say who first set a wooden disc turning on an axle, yoked oxen to a plough or raised a sail, but together these devices let early societies move more grain, more goods and more people than human backs ever could.

The wheel came surprisingly late, and probably to potters first. Wheeled vehicles appear across a wide area almost at once around 3500 to 3300 BCE: a clay pot from Bronocice in Poland bears what looks like a four-wheeled wagon, pictographs at Uruk show wheeled sledges, and a solid wooden wheel from the Ljubljana Marshes in Slovenia, dated to around 3150 BCE, is the oldest yet found. These early wheels were heavy discs pulled by oxen at walking pace. The light spoked wheel arrived around 2000 BCE on the steppes east of the Urals, and with it the war chariot. In the Americas, wheels turned up on Mesoamerican clay toys but never on carts; with no horses or oxen to pull them, there was little to gain.

The plough mattered even more to most people. The simple ard, a pointed wooden blade dragged through the soil by a pair of oxen, spread through Mesopotamia and Egypt in the fourth millennium BCE. A farmer with animals could till several times the land a family with hoes could manage, producing the surpluses that fed priests, soldiers and scribes. It reshaped households too: heavy ox-ploughing became largely men's work, and some scholars, following the economist Ester Boserup, link it to sharper divisions of labour between the sexes.

The sail turned rivers and seas into highways. The Nile was a perfect training ground: its current flows north while the prevailing wind blows south, so boats drifted downstream and sailed back up. Egyptian pots of around 3300 BCE already show boats with sails, and on the Gulf, Mesopotamian merchants traded with Dilmun, modern Bahrain, and onward to the Indus. Over the following millennia, sail power carried Austronesian voyagers from Taiwan across the Pacific and as far west as Madagascar, among the greatest seaborne migrations in history.

Did you know? The Ljubljana Marshes wheel, made of ash with an axle of oak, is more than 5,000 years old.

Combine them and the scale of the possible changed. Barges supplied Uruk along its canals; ox-carts hauled harvests to temple granaries; ships carried copper from Oman and cedar from Lebanon. Empires depend on moving tax grain, soldiers and orders faster than their rivals, and every one that followed, from Akkad to Rome to the Inca with their roads and llama trains, relied on some version of this quiet machinery.

Civilisation, at bottom, is a logistics problem.

Cities of Gods

In the early cities the tallest building was almost never the king's house. It was the home of a god. At Uruk, the whitewashed White Temple stood on a platform about 12 metres high before 3000 BCE, visible for miles across the flat plain. Over the following centuries such platforms grew into the ziggurat, a stepped mountain of mud brick that rose above every major Mesopotamian city.

The best preserved is the ziggurat of Ur, begun by King Ur-Nammu around 2100 BCE and completed by his son Shulgi for Nanna, the moon god and patron of the city. Its base measured about 64 by 46 metres. Its core was sun-dried brick, cased in a thick skin of baked brick set in bitumen, pierced by holes to let water drain from inside. Three great stairways met at the first terrace, and a shrine probably crowned the top, perhaps 30 metres above the ground. Leonard Woolley excavated it in the 1920s and 1930s, and its lower stages were partly rebuilt in the 1980s.

A ziggurat was not a church for congregations. Ordinary people did not worship at the summit; temple shrines housed the god's statue, which priests fed, clothed and washed every day. Sumerians believed humans had been created to labour for the gods, and the temple was the god's household. It owned fields, flocks, workshops and storerooms, employed hundreds of workers paid in rations of barley, oil and wool, and kept the accounts that had given rise to writing.

Kings ruled as the gods' stewards. A Sumerian ruler might be called ensi, governor on behalf of the city's god; he rebuilt temples, led festivals and claimed victories in divine names. Religion and government were not separate departments. In Egypt the bond was tighter still: the pharaoh was himself divine, the son of Ra, standing between his people and the cosmic order.

Did you know? The first author known by name is Enheduanna, daughter of Sargon of Akkad and high priestess of the moon god at Ur around 2300 BCE.

The pattern recurs across the world, apparently independently. At Caral in Peru, from around 2600 BCE, builders raised great platform mounds and sunken plazas without pottery or writing. Later Mesoamerican cities from Teotihuacan to Tikal set temple-pyramids at their centres, and Shang kings in China ruled through ancestral rites and oracle bones. Monumental religion made a city's order look eternal: a mountain built by hand, announcing that the gods had chosen this place and these rulers.

Babylon's great ziggurat, Etemenanki, probably inspired the biblical story of the Tower of Babel. That tale reads such towers as human pride. Many historians think their builders saw them the other way round: as a stairway for the gods to come down.

The skyline was a statement of faith, and of who was in charge.

Bronze Age Collapse

For much of the 13th century BCE, the eastern Mediterranean worked like an interlocking machine. Egypt, the Hittite empire in Anatolia, Babylon, Assyria, the Mycenaean palace kingdoms of Greece, and rich trading ports such as Ugarit on the Syrian coast and Alashiya on Cyprus exchanged letters, princesses, gold, grain and, above all, metal. Bronze needs copper and tin, roughly nine parts to one, and the two rarely occur together: copper came largely from Cyprus, tin from far to the east, much of it apparently from Central Asia. The Uluburun shipwreck off southern Turkey, from around 1300 BCE, carried about ten tonnes of copper and one tonne of tin, along with glass, ivory, ebony and Baltic amber.

Then, within a few decades either side of 1200 BCE, much of this world came apart. Hattusa, the Hittite capital, was abandoned and burned around 1180 BCE, and the empire vanished. Ugarit was destroyed around 1185 BCE and never reoccupied; among its last tablets are urgent letters about enemy ships. The Mycenaean palaces at Pylos, Mycenae and Thebes were destroyed or abandoned, and with them their script, Linear B; Greece would be without writing for some four centuries. Egypt survived, but only just.

Egyptian records blame invaders. Inscriptions at Medinet Habu describe how, in his eighth year, around 1177 BCE, Ramesses III defeated a coalition of 'Sea Peoples', naming groups such as the Peleset, Sherden and Shekelesh, who came by land and sea, some with families and ox-carts. The Peleset are usually identified with the Philistines, who settled on the coast of Canaan. But raiders alone cannot explain why so many strong states fell at once.

Most historians now see a systems collapse, with several stresses arriving together. Pollen from lake and sea cores across the region points to a long, severe drought around 3,200 years ago, bringing famine; Hittite rulers asked Egypt for shipments of grain. A cluster of earthquakes may have damaged cities. Trade routes broke, and palace economies that depended on imported metal and centrally redistributed food had no slack. Revolt, migration and raiding then fed on each other. In a tightly linked network, each failure made the next more likely.

Did you know? Linear B, the Mycenaean script lost in the collapse, was deciphered only in 1952, by Michael Ventris, an English architect.

The aftermath was not only loss. Iron, which could be found locally almost everywhere, spread as bronze supplies faltered. Smaller, nimbler societies filled the vacuum: the Phoenician cities, Israel, the Aramaeans and the Neo-Hittite states. In Greece, the long Dark Age ended in the city-state and the alphabet. The archaeologist Eric Cline's book 1177 B.C. turned the collapse into a parable of globalised fragility, a reading still widely debated.

When everything depends on everything else, it can all fall together.

The Alphabet Spreads

Writing in the Bronze Age was a professional skill. Cuneiform used several hundred signs, Egyptian hieroglyphs some 700 or more in their classic form, and mastering either took years in a scribal school. Writing belonged to temples, palaces and the scribes who served them. The alphabet changed that by doing something radically simple: one sign for each sound.

Its roots lie in Egypt. Around 1900 to 1800 BCE, Semitic-speaking workers in Egypt and Sinai, at the turquoise mines of Serabit el-Khadim and at Wadi el-Hol, borrowed a handful of hieroglyphs and gave them new values. The picture of an ox head, 'alp in their language, stood for its first sound; a house, bet, stood for 'b'. This acrophonic principle meant that a couple of dozen signs could write any word.

For centuries the script stayed marginal. Its breakthrough came with the Phoenicians, the seafaring Canaanites of Byblos, Tyre and Sidon who rose to dominate Mediterranean trade after the Bronze Age collapse. By around 1050 BCE they had settled on an alphabet of 22 letters, all consonants, written right to left. The inscription on the sarcophagus of King Ahiram of Byblos, from around 1000 BCE, is one of its earliest long texts. It suited merchants perfectly: quick to learn, quick to write on papyrus, potsherds or wax, and adaptable to almost any tongue.

Phoenician ships and colonies, from Cyprus to Carthage and Cádiz, carried the letters west. Around 800 BCE the Greeks adopted them, a borrowing Herodotus credited to the legendary Phoenician Cadmus, and made one crucial change: they turned letters for sounds Greek did not use into vowels, so that 'alp became alpha, A. The Etruscans took Greek letters to Italy, and the Romans adapted them into the Latin alphabet, now the most widely used script on Earth. Greek was also the parent of Cyrillic, devised for Slavic languages around the ninth and tenth centuries CE.

Did you know? The Greek word for papyrus, byblos, came from the Phoenician port that traded it, and gave English the word 'Bible'.

Eastward, the Aramaic form of the alphabet became the everyday script of the Assyrian and Persian empires and the ancestor of the Hebrew square letters, Syriac and, through Nabataean, Arabic. Many scholars think the Brahmi script of ancient India, ancestor of Devanagari and much South and Southeast Asian writing, was also inspired by Aramaic, though that is debated. China kept its own logographic writing, unbroken for more than 3,000 years.

The consequences came slowly but went deep. Literacy stayed a minority skill for millennia, yet an alphabet could be learned in weeks rather than years, by traders, soldiers and craftsmen as well as priests. Writing had left the temple, and it never went back.

Twenty-two letters opened the written word to everyone who cared to learn.

Writing Outlives Empire

Every civilisation described so far fell. Sumer's cities were conquered by Akkad and absorbed by Babylon; the Indus cities emptied; the Hittites and Mycenaeans vanished in the Bronze Age collapse; Egypt's pharaohs gave way to Persians, Macedonians and Romans. Yet almost everything they invented is still in daily use, from the wheel under a lorry to the alphabet on this page.

What survived was not power but ideas, and the surest way for an idea to survive is to be written down and copied. Cuneiform outlived Sumerian as a spoken language by some two thousand years: scribes kept learning Sumerian as a classical tongue, much as medieval Europe kept Latin, and the last datable cuneiform tablet, an astronomical text, comes from around 75 CE. The Epic of Gilgamesh, first told in Sumerian poems written down around 2100 BCE, was still being copied more than a thousand years later for the library of the Assyrian king Ashurbanipal at Nineveh.

Destruction sometimes helped. When Babylonians and Medes sacked Nineveh in 612 BCE, the burning palaces baked many clay tablets harder. Excavated from 1849, some 30,000 tablets and fragments reached the British Museum, and in 1872 a young assistant there, George Smith, recognised among them a flood story strikingly close to Noah's.

Did you know? The Rosetta Stone, found in 1799 and cracked by Jean-François Champollion in 1822, repeats one priestly decree in hieroglyphs, demotic and Greek.

The keys to reading these worlds were recovered only recently. Henry Rawlinson and others deciphered cuneiform in the 1850s, using the trilingual inscription of the Persian king Darius at Behistun in Iran. Linear B fell in 1952. The Indus script remains unread, a reminder that a civilisation without a surviving key can still go unheard.

Some legacies are so familiar they have become invisible. The 60-minute hour and the 360-degree circle come from Mesopotamian mathematics. Egypt's 365-day year, passed through Julius Caesar's reform, underlies the modern calendar. Written law, from Ur-Nammu and Hammurabi onward, made justice something that could be cited. The alphabet, the city, the plough and the sail became common property of humanity, carried across languages, faiths and borders by people who rarely knew where they had come from.

The lesson is not that empires were pointless. States dug the canals, paid the scribes and guarded the trade routes that let ideas spread. But the dynasties were scaffolding; the ideas were the building. The age that followed, of philosophers, prophets and larger empires, would build on foundations laid by people whose names, in many cases, are lost.

Kingdoms die. Good ideas get copied.

The Axial Age

Between roughly 800 and 300 BCE, in places that barely knew of one another, thinkers began asking the same unsettling questions. What makes a life good? Is justice more than obedience? Can one person be right when the king, the priest and the crowd are all wrong? The German philosopher Karl Jaspers gave this stretch of time a name in 1949: the Axial Age, the hinge on which human thought turned.

In China the old Zhou order was crumbling into rival states, and Confucius (traditionally 551–479 BCE) wandered between courts offering advice that rulers mostly ignored. His answer to chaos was character: rulers who governed by example, families bound by respect, rituals performed with sincerity. "What you do not want done to yourself, do not do to others," he told a student, in a line the Analects preserved. At around the same time, the followers of Laozi urged the opposite instinct: let go, follow the Way, do less.

On the Ganges plain, among new cities and new kingdoms, Siddhartha Gautama, the Buddha, lived around the fifth century BCE, although his exact dates are disputed. A prince by tradition, he left comfort to confront suffering, and taught that craving was its root and a disciplined middle path its cure. His contemporary Mahavira, the great teacher of Jainism, pressed non-violence to its limit, while the Upanishads explored the self and ultimate reality.

In Israel and Judah, prophets such as Amos, Isaiah and Jeremiah thundered that God wanted justice for widows and orphans more than sacrifice. The shock of the Babylonian exile after 586 BCE turned Judaism into a faith of sacred text and law. In Greece, philosophers from Thales onwards sought natural explanations for the world, and in Athens Socrates (c. 470–399 BCE) questioned everyone in the marketplace until the city tried and executed him. "The unexamined life is not worth living," he told his jurors, in Plato's account.

Why then? Historians point to iron tools and bigger harvests, the spread of coinage and cities, and centuries of brutal warfare that made old certainties look thin. Some scholars doubt the Axial Age was one event at all, and see instead several separate breakthroughs gathered under a tidy label. Zoroaster, often added to the list, has dates too uncertain to place him confidently inside it.

Did you know? None of the three most famous Axial teachers left a book of his own: the Analects, the Buddhist suttas and Plato's dialogues were all set down by followers.

What is not in doubt is the legacy. Confucianism, Buddhism, Judaism and Greek philosophy shaped the states and empires of the chapters that follow, from Han China to Rome, and later fed into Christianity and Islam. Four conversations began in four languages. None of them has finished.

Athens Tries Democracy

In 508 or 507 BCE an aristocrat named Cleisthenes won a bitter political struggle in Athens by doing something unusual: he took the side of the ordinary people. His reforms broke the power of the old clans by redrawing Attica into ten new tribes, each mixing city, coast and inland villages. On that base Athens built the machinery of demokratia, "rule by the people".

The heart of it was the Assembly, the ekklesia, which met on the rocky hill of the Pnyx around forty times a year. Any adult male citizen could attend, speak and vote, usually by a show of hands, on war and peace, treaties, taxes and laws. A Council of 500, fifty men from each tribe chosen by lot for a year, prepared its business. Juries of hundreds of citizens, also chosen by lot and paid a small daily fee from the 450s BCE, decided cases without professional judges. Lot, not election, was the democratic method: it gave every citizen an equal chance and the rich no edge. Only posts that needed expertise, such as the ten generals, were elected, and Pericles was chosen general year after year.

Once a year citizens could also vote to ostracise a dangerous man by scratching his name on a pottery shard, an ostrakon. If enough votes were cast, 6,000 by most accounts, the man named most often went into exile for ten years, though he kept his property.

The limits were stark. Women could not vote; nor could the many enslaved people, nor the resident foreigners, the metics, who traded and fought for the city. Of perhaps 250,000 to 300,000 people in Attica, only some 30,000 to 50,000 adult men were citizens, and after 451 BCE citizenship required two Athenian parents. Athenian wealth rested partly on silver mines at Laurion worked by slaves, and on tribute from allies in its maritime empire.

Nor was the people always wise. In 427 BCE the Assembly voted to kill all the men of rebellious Mytilene, then changed its mind the next day; a second ship arrived just in time. It launched the disastrous Sicilian expedition in 415 BCE, and in 399 BCE a jury of 501 citizens condemned Socrates. Critics from Plato onwards called democracy the rule of the mob.

Did you know? Archaeologists found around 190 ostraka bearing the name of the general Themistocles, written in only a handful of hands: ballots, it seems, prepared in advance for voters.

Yet the experiment lasted, with interruptions, for nearly two centuries, until Macedon curtailed it in 322 BCE, and other Greek cities ran democracies of their own. Its central claim, that ordinary people can run their own affairs, outlived it, and Rome's republic offered a rival answer to the same question. Athens did not get democracy right. It got it started.

The Persian Superpower

Around 550 BCE the king of a small realm in what is now southern Iran, Cyrus II, overthrew his Median overlord. Within a few years he had taken Lydia and its gold-rich capital Sardis, and in 539 BCE he entered Babylon, the greatest city of the age. His son Cambyses added Egypt in 525 BCE. The Achaemenid Empire, named after the dynasty's legendary ancestor, now stretched from the Nile and the Aegean to the Indus: perhaps 5 million square kilometres and, on very rough estimates, somewhere between 17 and 35 million people.

Conquering was one thing; holding was another. The great organiser was Darius I (r. 522–486 BCE). He divided the empire into provinces called satrapies, around twenty by Herodotus' count, each run by a satrap, usually a Persian noble. To keep satraps honest, garrison commanders and royal secretaries reported to the king separately, and inspectors known as the "King's Eye" toured the provinces. Each satrapy owed a fixed tribute in silver or in kind: Herodotus lists white horses from Cilicia and gold dust from India.

Darius bound it all together with roads. The Royal Road ran some 2,700 kilometres from Sardis to Susa, with 111 staging posts, according to Herodotus. Ordinary travellers took around three months; relays of royal couriers on fresh horses covered it in perhaps a week. Darius also issued a standard gold coin, the daric, and his scribes used Aramaic as a common administrative language across dozens of tongues. At Persepolis, begun around 518 BCE, stone reliefs show delegations from across the empire, Ethiopians, Indians and Ionian Greeks among them, bringing gifts to the king.

The secret was restraint. The Persians let subjects keep their languages, laws and gods as long as they paid and obeyed. Cyrus presented himself in Babylon as the chosen one of its god Marduk, and his inscribed clay Cyrus Cylinder records the return of displaced peoples and their sacred images. The Hebrew Bible remembers him as the king who let the Jews go home from exile and rebuild the Temple in Jerusalem. Calling this a charter of human rights, as some modern admirers do, goes too far. It was shrewd imperial policy, and it worked.

Did you know? Herodotus' praise of the Persian couriers, whom "neither snow nor rain nor heat nor gloom of night" could stop, is inscribed in English on New York's James A. Farley Post Office.

The empire was not invincible. Greek cities beat Persian invasions at Marathon in 490 BCE and Salamis in 480 BCE, and royal successions were often bloody. In 330 BCE Darius III was murdered by his own officers while fleeing Alexander, whose story comes next. But the model of a multi-ethnic state held together by roads, posts, tribute and tolerance outlived the dynasty, and later empires from the caliphs to the Mongols borrowed its toolkit. It was the first superpower, and it ruled like one.

Alexander's Fusion

Alexander III of Macedon was twenty when his father, Philip II, was assassinated in 336 BCE, leaving him a superb army and a plan to invade Persia. In 334 BCE he crossed the Hellespont into Asia with around 40,000 men. He beat a Persian force at the Granicus River that year, defeated Darius III in person at Issus in 333 BCE, took the island city of Tyre after a seven-month siege and entered Egypt, where he founded Alexandria around 331 BCE. Later that year, at Gaugamela near modern Mosul, he broke the Persian royal army for good.

Then he kept going. Persepolis burned in 330 BCE. Three hard years in Bactria and Sogdiana, today's Afghanistan and Uzbekistan, ended with his marriage to Roxana, a local noblewoman. In 326 BCE he crossed into the Punjab and defeated King Porus and his war elephants at the Hydaspes. At the Hyphasis, the modern Beas, his exhausted soldiers refused to go any further, and he turned back, losing many men on a march through the Gedrosian desert. He died in Babylon in June 323 BCE, aged 32, probably of fever or illness rather than the poison rumoured at the time.

His empire did not survive him. His generals, the Diadochi or "successors", fought for decades and carved it into kingdoms: the Ptolemies in Egypt, the Seleucids from Syria to Iran, the Antigonids in Macedon. Yet what they ruled was something new. Historians call it the Hellenistic world, the age of Greek culture spread far beyond Greece, which lasted until Rome absorbed the last of these kingdoms after the battle of Actium in 31 BCE.

Alexander had already blurred the line between conqueror and conquered. He adopted elements of Persian royal dress and court ritual, to his Macedonians' disgust, and at Susa in 324 BCE held a mass wedding at which some ninety of his officers married Persian and Iranian noblewomen. Greek settlers followed into new cities, many named Alexandria. A common Greek, the koine, became the language of trade and learning from Sicily to Bactria. In Ptolemaic Alexandria a great Library gathered scholars, Euclid wrote his Elements, and Jewish scholars translated the Hebrew scriptures into Greek, the version known as the Septuagint.

Did you know? At Ai Khanoum, a Greek city in northern Afghanistan, a stone base carried moral maxims copied at Delphi, more than 4,000 kilometres away, set up by a man named Clearchus.

The fusion ran both ways. In Gandhara, in today's Pakistan and Afghanistan, Buddhist sculptors later carved the Buddha with Greek-style drapery and curls, among the earliest images of him in human form. A Greek king of India, Menander, appears in a Buddhist text as a royal questioner of a monk. The New Testament would be written in koine Greek. The sword won Alexander an empire in eleven years. The shared language and cities kept its culture alive for centuries.

The Roman Republic

According to Roman tradition, in 509 BCE the people of Rome drove out their last king, Tarquin the Proud, and swore never to be ruled by one man again. The story is half legend, but hatred of the word rex, king, became the founding instinct of the state. In place of a monarch the Romans built the res publica, "the public thing", a system designed so that nobody could hold too much power for too long.

At the top stood two consuls, elected every year. They commanded the armies and presided over government, but each could veto the other, and after twelve months they returned to private life, where they could be prosecuted for abuses. Below them a ladder of elected offices, the cursus honorum, ran through quaestor, aedile and praetor, with minimum ages and gaps between posts. In an emergency a dictator could be appointed for no more than six months; legend made a hero of Cincinnatus, who in 458 BCE saved the city and went back to his plough.

The Senate, about 300 former magistrates sitting for life, could not pass laws, but its advice on finance, foreign policy and war was rarely ignored. Laws and elections belonged to the citizens in their assemblies, though votes were counted by groups weighted towards the wealthy. A long struggle between patricians and plebeians, the Conflict of the Orders, won the commoners officers of their own, the tribunes of the plebs, from 494 BCE. A tribune's person was sacrosanct, and his single word veto, "I forbid", could stop a magistrate in his tracks. Around 450 BCE the law itself was written down on the Twelve Tables and displayed in public.

The Greek historian Polybius, a hostage in Rome in the second century BCE, thought this mixed constitution, part monarchy, part aristocracy, part democracy, explained how one city had come to master the Mediterranean. Yet success strained it. Conquest brought slaves, plunder and huge armies loyal to their generals rather than the state. The reforming Gracchus brothers were killed in 133 and 121 BCE; Marius and Sulla turned the legions on Rome itself. Julius Caesar crossed the Rubicon in 49 BCE, was made dictator for life, and was stabbed to death in a meeting of the Senate in 44 BCE. His adopted heir Octavian became Augustus in 27 BCE, keeping the republic's forms while holding its power.

Did you know? The authors of the Federalist Papers, which argued for the US Constitution in 1787 and 1788, signed themselves "Publius", after Publius Valerius Publicola, a founder of the Roman Republic.

The republic lasted almost five centuries, longer than any modern republic so far. Its vocabulary is everywhere: senate, veto, consul, even candidate, from the bright white toga, the toga candida, worn by men seeking office. So is its central idea, that office should be temporary and power checked by power. The founders of the United States and of revolutionary France looked back to Rome deliberately. Their constitutions are its descendants.

Roads, Law, Concrete

Rome conquered with legions, but it governed with engineers and lawyers. In 312 BCE the censor Appius Claudius Caecus began two projects that set the pattern: the Via Appia, a paved military road running south towards Capua, and the Aqua Appia, the city's first aqueduct. Both still carry his name.

Roads came first because armies needed them. Surveyors drove them as straight as the land allowed; builders laid them in layers of large stones, rubble and gravel, topped with fitted paving and cambered to shed the rain, though methods varied from province to province. Milestones marked every Roman mile of a thousand paces, about 1.48 kilometres. At its height the empire had some 80,000 kilometres of major paved highways, by common estimates, from Hadrian's Wall to the Euphrates. Soldiers, officials, merchants and imperial couriers all used them, and so, in time, did new ideas and new religions.

Water made Roman cities possible. By the early third century CE eleven aqueducts supplied Rome, bringing water from hills up to 90 kilometres away down a gentle, carefully surveyed gradient, mostly in underground channels rather than on the famous arches. The water commissioner Frontinus, writing around 97 CE, compared these indispensable works favourably with the "idle pyramids" of Egypt. The Pont du Gard in southern France, about 49 metres high, still stands, its great stones laid without mortar.

The material behind much of Rome's building was Roman concrete, opus caementicium: lime mortar mixed with a volcanic ash called pozzolana and chunks of rock. It could be poured into wooden forms, it set even under water, which made harbours such as Herod's Caesarea possible, and it freed architects to build vaults and domes. The Pantheon, rebuilt under Hadrian around 125 CE, has a dome 43.3 metres across with an open oculus at its crown. Nearly 1,900 years later it is still the largest unreinforced concrete dome in the world.

Did you know? Some Roman harbour concrete has grown stronger in seawater over two thousand years, as new minerals crystallised in its pores, a process modern materials scientists have studied closely.

Law was the fourth pillar. From the Twelve Tables onwards, Roman jurists refined rules for property, contracts, inheritance and wrongs, and developed a "law of nations" for dealing with foreigners. In 212 CE Emperor Caracalla granted citizenship to almost all free inhabitants of the empire, bringing millions under Roman law. In the 530s CE the eastern emperor Justinian had the whole tradition compiled into what became known as the Corpus Juris Civilis. Rediscovered at Bologna in the late eleventh century, it became the foundation of the civil law of most of continental Europe and, through European influence, of much of Latin America, Africa and East Asia.

The four reinforced one another: roads moved troops and taxes, aqueducts fed cities, and cities ran on law. Together they let a single city govern the Mediterranean for centuries. Stretches of the Via Appia can still be walked today.

The Han Mirror

In 206 BCE China's first imperial dynasty, the harsh Qin, collapsed barely fifteen years after unifying the country. From the civil war that followed emerged a minor official of peasant birth, Liu Bang, who in 202 BCE became Emperor Gaozu of the Han dynasty. With one short interruption, the Han ruled for four centuries, until 220 CE, a span that matches Rome's growth from republic to imperial peak.

The two empires were remarkably alike in scale. A Han census of 2 CE counted about 57.7 million people; the Roman Empire at around the same time held perhaps 45 to 60 million, though that figure is a modern estimate. Both built roads and walls, fielded huge armies, minted coins in vast numbers and taxed peasant farmers to pay for it all. Both faced restless frontiers: Rome the Germanic peoples, the Han the powerful Xiongnu confederacy of the steppe, sometimes fought, sometimes bought off with silk and princesses.

Where they differed most was in how they governed. Rome ran its provinces with a thin layer of senators, equestrians and city councils, and leaned heavily on local elites. The Han built a salaried bureaucracy whose ranks were measured in units of grain. Emperor Wu (r. 141–87 BCE) made Confucianism the state's official learning and in 124 BCE founded an Imperial Academy to train officials in the classics. Candidates were mostly recommended by local officials as "filial and incorrupt", then tested; the full competitive examination system came only centuries later, under the Sui and Tang. Still, the principle that officials should be educated, and promoted for ability and virtue, took deep root.

Wu was an aggressive ruler too. He drove back the Xiongnu, pushed Han power into Korea, northern Vietnam and the Tarim Basin, and set up state monopolies on salt and iron to pay for it. His envoy Zhang Qian, sent west around 138 BCE, returned years later with news of Central Asia and its fine horses, opening the routes later called the Silk Roads. The historian Sima Qian wrote his vast Records of the Grand Historian during Wu's reign, and around 105 CE the court official Cai Lun was credited with improving the making of paper.

Did you know? In 97 CE the Han general Ban Chao sent an envoy, Gan Ying, to reach the Roman world; he got as far as a western sea, was told the crossing could take years, and turned back.

Each empire knew the other mainly as rumour. Romans prized Chinese silk without knowing much about its makers, and Chinese chronicles described a distant land called Da Qin. A party claiming to come from its ruler, Andun, probably Marcus Aurelius Antoninus, reached the Han court by sea in 166 CE. Both empires broke apart in the following centuries. But China was reunited under the Sui in 589 on Han foundations, and most Chinese people still call themselves Han. Rome's west was never put back together.

Empire Buys Peace

When Augustus took sole power in 27 BCE after decades of civil war, Romans were exhausted. He offered them peace, and he advertised it. The doors of the Temple of Janus, kept open in wartime, were closed three times in his reign, by his own account. The Senate dedicated the Ara Pacis, the Altar of Augustan Peace, in 9 BCE. Historians later gave the two centuries from 27 BCE to the death of Marcus Aurelius in 180 CE a name: the Pax Romana, the Roman Peace.

Inside the frontiers the peace was real. Piracy, which had once kidnapped the young Julius Caesar, was swept from the Mediterranean, which Romans now called mare nostrum, "our sea". Grain from Egypt and North Africa fed a capital of perhaps a million people. Olive oil from Spain arrived in amphorae so numerous that their broken shards form Monte Testaccio, an artificial hill in Rome about 35 metres high. Roman ships sailed with the monsoon from Red Sea ports to India, and Pliny the Elder complained that India, China and Arabia drained the empire of 100 million sesterces a year. Across the provinces cities built forums, baths and theatres, and local elites competed to become Roman.

The peace was guarded by around thirty legions, with as many auxiliaries again, perhaps 300,000 to 400,000 soldiers in all, stationed mostly along the frontiers. Provincial taxes paid for them. A shared coinage, shared weights and measures and Roman courts made trade easier, and a citizen could appeal over a governor's head, as the apostle Paul famously did, to Caesar.

Yet the calm had hard edges. Rome lost three legions in Germany's Teutoburg Forest in 9 CE. Boudica's revolt in Britain around 60 CE destroyed three towns before it was crushed. The Jewish War ended with the destruction of the Temple in Jerusalem in 70 CE, and the Bar Kokhba revolt of 132 to 135 CE was suppressed with enormous loss of life. In Rome, emperors such as Caligula and Nero terrorised the elite, and in 69 CE four emperors ruled in a single year. From 122 CE Hadrian built his wall across northern Britain, a frank admission that the empire had limits.

Did you know? Tacitus gave the sharpest verdict on the Roman Peace to a British chieftain, Calgacus, whose speech he composed: "They make a desert and call it peace."

Was it worth the price? Many provincials seem to have thought so, and inscriptions across the empire hail emperors as bringers of prosperity. Others lost their land, their freedom or their lives. Similar bargains appear wherever one power dominates, from Han China's frontier diplomacy to the empires of the modern age. The long peace was already fraying when plague and wars on the Danube marked Marcus Aurelius's final years, opening the story of Rome's decline. Peace under empire can be genuine. Someone always pays for it.

Why Rome Fell

In 476 CE a Germanic general named Odoacer deposed a teenage emperor, Romulus Augustulus, and sent the imperial regalia to Constantinople. Few people at the time thought the world had ended. That is the first clue: the fall of the Western Roman Empire was a process that took centuries, not a single day, and the eastern empire, which historians call Byzantium, lasted until 1453.

Historians have argued about the causes ever since Edward Gibbon published The History of the Decline and Fall of the Roman Empire between 1776 and 1789. The German historian Alexander Demandt once collected 210 explanations that had been offered over the years, from lead poisoning to moral decay. Most scholars today see several pressures that fed one another.

The first was sheer size. Frontiers thousands of kilometres long, from Scotland to the Sahara, needed huge armies, and armies made and unmade emperors. In the Crisis of the Third Century, from 235 to 284 CE, more than twenty men were recognised as emperor, most of them dying violently, and for a time the empire split into three. The second was disease. The Antonine Plague from 165 CE, possibly smallpox, killed perhaps a tenth or more of the population, on estimates that vary widely, and the Plague of Cyprian struck again from around 249.

The third was money. To pay the soldiers, emperors stretched the silver. A denarius under Augustus was almost pure silver; by around 270 CE the main coin, the antoninianus, held only a few per cent. Prices rose, trust collapsed and taxes were increasingly collected in kind. Diocletian (r. 284–305) restored order by sharing power among four emperors and enlarging the bureaucracy, and in 301 tried to fix prices by decree. Constantine refounded Byzantium as Constantinople in 330, shifting the empire's centre of gravity east.

The fourth pressure came from outside. Pushed partly by the Huns, Gothic refugees crossed the Danube in 376, and in 378 destroyed a Roman army at Adrianople, killing Emperor Valens. After 395 the empire was permanently divided between east and west. Vandals, Alans and Sueves crossed the Rhine around 406; the Visigoth Alaric sacked Rome in 410, the first time in some 800 years an enemy had taken the city; the Vandals seized Carthage, capital of the West's richest province, in 439, and sacked Rome again in 455. Without African taxes the western government could not pay the armies that defended it.

Did you know? The word "vandalism" was coined in 1794 by the French bishop Henri Grégoire, protesting at revolutionary destruction, and pinned the Vandals' name unfairly to mindless wreckage.

For many people in Gaul, Spain and Italy, life under new Gothic, Frankish or Vandal kings changed slowly; Latin, Roman law and the Church carried on. Some historians call this a transformation, while others point to collapsing trade, cities and living standards. Both can be true. Empires rarely die of one blow. They bleed.

The Classical Debt

Open a newspaper and the classical world is everywhere. Democracy and politics are Greek words; republic, senate, citizen and constitution are Latin. So are many of the habits behind them: argument from evidence, voting, written law, trial by jury, and the idea that a political community belongs to its members rather than to its ruler.

The Greeks contributed questions and methods. Athens gave the radical idea that ordinary citizens could govern themselves. Socrates made questioning a way of life, Plato imagined an ideal state, and Aristotle (384–322 BCE) set out formal logic in the syllogism, while his school collected the constitutions of some 158 Greek states. Euclid's Elements taught geometry by proof from axioms, and doctors in the Hippocratic tradition looked for natural causes of disease. Rome added institutions that endured: the republic's checks and balances, a professional tradition of law, and a citizenship that could be extended to people who were neither born in the city nor spoke its language.

The inheritance did not flow straight to the present. After the western empire collapsed, much Greek learning survived in Byzantium and, crucially, in the Islamic world. In ninth-century Baghdad scholars such as Hunayn ibn Ishaq translated Aristotle, Galen and Ptolemy into Arabic. Later Ibn Rushd of Córdoba, known in Europe as Averroes, wrote commentaries on Aristotle so influential that Latin scholars called him simply "the Commentator". From the twelfth century translators in Toledo and Sicily turned these works into Latin, feeding Europe's new universities and, later, the Renaissance.

Revolutionaries borrowed eagerly. The American founders wrote as "Publius", built a Senate and housed their government in a Capitol. French revolutionaries dressed their republic in Roman symbols, and Napoleon's Civil Code of 1804 drew heavily on Roman law. Columns and pediments still front parliaments, courthouses and banks on every continent.

Did you know? The Virginia State Capitol, designed by Thomas Jefferson in the 1780s, was modelled on the Maison Carrée, a Roman temple at Nîmes in France that still stands.

The debt has to be read with care. Athenian democracy excluded women and depended on slavery; Rome's republic was dominated by the rich and built on conquest. "The West" is a much later idea that claimed the classics as its private property, when Arabic, Persian, Syriac and Byzantine scholars had kept much of them alive. Other classical worlds left legacies just as large: the Confucian scholar-official state shaped East Asia for two thousand years, and Buddhism spread from India across the continent.

Still, every time a vote is held, a law is challenged in court or a citizen asks by what right the powerful act, the classical age is speaking. The arguments are old. They are not over.

One God Rising

Most peoples of the ancient world lived among crowds of gods: gods of storms, rivers, cities and harvests, each to be fed, flattered or feared. In the hill country of Canaan, a small people slowly came to a different conviction. By the end of the Babylonian exile, the Israelites held that there was one God, creator of everything, who cared less for sacrifices than for justice, and who bound a whole people to a moral law.

The idea did not arrive fully formed. Early Israelite religion seems to have honoured one god above others, and the Hebrew Bible itself records long struggles against the worship of Baal and Asherah. Egypt's pharaoh Akhenaten had imposed the worship of the sun disc Aten around 1350 BCE, and Persia's prophet Zoroaster, whose dates are much debated, taught a supreme god of truth, but neither idea outlived its moment in the same way.

The decisive test came in 587 or 586 BCE, when Nebuchadnezzar II of Babylon destroyed Jerusalem and its Temple and carried the elite into exile. A god tied to one land and one temple should have died with them. Instead, in Babylon, priests and scribes sharpened the belief that their God ruled every land, Babylon included. Much of the Torah, the first five books of scripture, took its lasting shape in these years and after 539 BCE, when the Persian king Cyrus the Great allowed the exiles to return. A faith that could survive without a temple could travel anywhere.

That portability proved its strength. When Rome destroyed the Second Temple in 70 CE, Judaism reorganised around the synagogue, the rabbi and the study of texts, producing the Mishnah and, later, the vast Talmud. Meanwhile two great branches grew from the same root. Christianity began around 30 CE as a Jewish movement following Jesus of Nazareth and carried the one God to the Gentile world. In 610 CE, in Mecca, Muhammad began to preach a revelation that placed itself in the line of Abraham, Moses and Jesus: Islam.

Did you know? The earliest known mention of Israel outside the Bible is a single line on the Merneptah Stele, an Egyptian victory monument of c. 1208 BCE now in the Egyptian Museum in Cairo.

The three are known together as the Abrahamic faiths, after the patriarch all three honour. Today Christians number roughly 2.4 billion and Muslims around 2 billion, while Jews number only about 15 million. Together they claim the loyalty of more than half of humanity.

What they inherited was more than arithmetic. If one God made all people, then all people shared a single moral standing, and kings, too, stood under a law higher than themselves. The prophet Amos condemned those who sold "the poor for a pair of shoes". Ideas of history as a story with a direction, of a covenant, and of a weekly day of rest spread with these faiths across the globe.

A small people, often conquered and rarely powerful, changed what billions believe.

Christianity Goes Global

Around 30 CE, in the Roman province of Judaea, a Galilean preacher named Jesus was crucified on the orders of the governor Pontius Pilate. Crucifixion was meant to end movements like his. Instead his followers proclaimed that he had risen, and within a generation small communities calling him the Messiah, Christos in Greek, met in cities from Jerusalem to Rome.

The movement travelled along the empire's own wiring. Roman roads, safe sea lanes and a shared koine Greek let a tentmaker named Paul of Tarsus found and nurture churches across Asia Minor and Greece in the 40s and 50s CE, and his letters are the oldest Christian writings to survive. Jewish communities scattered around the Mediterranean gave missionaries a first audience. Crucially, Paul argued that Gentile converts need not be circumcised or keep the food laws, which opened a Jewish sect to anyone.

Rome tolerated many gods but distrusted people who refused to honour its own. After the Great Fire of 64 CE, Nero blamed the Christians and had many put to death. For two centuries persecution was mostly local and sporadic, until Decius demanded empire-wide sacrifice in 250 and Diocletian launched the Great Persecution in 303. Martyrs became heroes, and their stories travelled faster than the decrees.

Why did the faith keep growing? Historians point to its networks of mutual aid, its care for the sick during epidemics such as the Plague of Cyprian in the 250s, its welcome to women, slaves and the poor, and its promise of personal salvation that civic cults did not offer. Estimates are uncertain, but Christians may have made up around a tenth of the empire's 60 million or so people by 300 CE.

Then came a political earthquake. In 312 Constantine won the Battle of the Milvian Bridge, later claiming he had fought under the sign of Christ. The Edict of Milan in 313 granted toleration. In 325 Constantine summoned the bishops to Nicaea to settle doctrine, and in 380 Theodosius I's Edict of Thessalonica made Nicene Christianity the official faith of the empire. The persecuted had become the established, and before long pagans and dissenting Christians were the ones under pressure.

Did you know? Rome was not the first state to adopt Christianity: the kingdom of Armenia did so first, traditionally in 301 CE, and the Ethiopian kingdom of Aksum followed under King Ezana in the 330s.

The faith was already spilling beyond Rome's frontiers. The Church of the East grew inside the Persian Empire and reached Tang China by 635. The Goths were converted in their own language by the missionary bishop Ulfilas, who devised an alphabet so that he could translate the Bible.

Conviction and networks had outrun the sword. Within four centuries, the cross had gone from a tool of execution to the emblem of an empire.

The Rise of Islam

Around 610 CE a merchant of Mecca named Muhammad, then about forty, began to recite revelations he said came from God through the angel Gabriel. Arabia then sat between two exhausted superpowers, Byzantium and Sasanian Persia, which had just fought each other almost to collapse. Its own peoples were divided into rival tribes, many of them honouring idols at the Kaaba in Mecca, a pilgrimage shrine at the heart of a trading town.

Muhammad's message was uncompromising: one God, a coming judgement, prayer, charity and the equality of believers. Mecca's elite, who profited from the pilgrim trade, pushed back hard. In 622 Muhammad and his followers moved north to Medina, a migration called the Hijra that marks year one of the Islamic calendar. There he became lawgiver and commander as well as prophet. By 630 Mecca had surrendered, and when he died in 632 most of Arabia was bound together for the first time by faith rather than kinship.

His successors, the caliphs, turned that unity outward. Arab armies beat the Byzantines at the Yarmuk in 636 and the Persians at al-Qadisiyya around the same time. Jerusalem fell in 637 or 638, Egypt by 642, and the Sasanian Empire collapsed by 651. Under the Umayyad dynasty, ruling from Damascus after 661, the advance went on: Carthage in 698, Iberia from 711, and Sindh in the Indus valley in 711 and 712. In barely a century a single state stretched from the Atlantic coast to the edge of India.

Conquest was not mass conversion. Christians, Jews and Zoroastrians were generally allowed to keep their faiths as protected peoples, the dhimmi, in return for a poll tax, the jizya. Many regions stayed mostly non-Muslim for centuries. What spread fastest was a framework: Arabic became the language of government under Caliph Abd al-Malik, new gold coins carried Qur'anic phrases instead of portraits, and the Dome of the Rock rose in Jerusalem in 691.

Did you know? Gibraltar takes its name from the Arabic Jabal Tariq, "Tariq's Mountain", after the Berber commander Tariq ibn Ziyad, who landed there in 711.

The expansion had limits. A Frankish army under Charles Martel halted a raiding force near Tours around 732, and the walls of Constantinople held through two great sieges. In 750 the Abbasids overthrew the Umayyads and shifted power east, towards Iraq and the Persian world. The next year an Abbasid army defeated a Tang Chinese force at the Talas River in Central Asia, near the eastern limit of Arab rule.

What emerged was a single zone of faith, law and commerce linking the Mediterranean to the Indian Ocean. A merchant could travel from Córdoba to Samarkand, pray towards the same city and trade under familiar rules. Its new capital would soon rise on the Tigris: Baghdad.

One lifetime, one faith, three continents.

The House of Wisdom

In 762 the Abbasid caliph al-Mansur laid out a new capital on the Tigris: Baghdad, a round city whose walls enclosed palace and mosque. Within decades it was among the largest cities on Earth, home to perhaps several hundred thousand people, and it sat where trade routes from the Mediterranean, Persia, India and China met. Wealth, curiosity and a practical need for astronomers, doctors and surveyors combined to launch one of history's great translation projects.

The House of Wisdom, the Bayt al-Hikma, is linked with Harun al-Rashid and above all his son al-Ma'mun, who ruled from 813 to 833. Historians debate exactly what it was, probably a palace library and translation bureau rather than a university, but its name became shorthand for a wider movement. Caliphs, viziers and wealthy families paid handsomely for manuscripts and translations. Works by Aristotle, Euclid, Ptolemy and Galen were rendered into Arabic, often by way of Syriac, by Christian scholars such as Hunayn ibn Ishaq, alongside Persian texts on statecraft and Indian works on mathematics and astronomy.

Cheap paper made it possible. Papermaking reached the Islamic world from China in the eighth century, traditionally through Chinese prisoners taken at the Battle of Talas in 751, a story historians treat with caution. Baghdad had paper mills by the 790s, and books became far cheaper than they had been on parchment or papyrus.

The scholars did not merely copy. Around 820 Muhammad ibn Musa al-Khwarizmi wrote a handbook on solving equations whose title gave us the word algebra, from al-jabr, "restoring". Another of his books explained the Indian decimal place-value system, with its symbol for zero, which the Indian mathematician Brahmagupta had already treated as a number in 628. Astronomers measured a degree of latitude on the plains of Iraq. Physicians such as al-Razi ran hospitals and kept clinical case notes, and al-Kindi wrote on optics, music and code-breaking.

Did you know? The word algorithm comes from Algoritmi, the Latin form of al-Khwarizmi's name, used in medieval translations of his book on Indian numerals.

The relay ran on. From the twelfth century, scholars in Toledo, newly in Christian hands, and in Norman Sicily translated Arabic texts into Latin; Gerard of Cremona alone produced dozens. In 1202 Fibonacci of Pisa, who had learned his arithmetic in North Africa, published the Liber Abaci, which introduced Hindu-Arabic numerals to European merchants. Europe had not entirely slept, since Byzantium still copied Greek texts and monasteries kept Latin ones, but much of its new science arrived with Arabic names: algebra, alchemy, zenith, cipher.

The Mongol sack of Baghdad in 1258 ended the city's golden age, and legend says the Tigris ran black with ink from drowned books. By then the knowledge had long since escaped. Baghdad had been less a vault than a relay station, and the baton reached the next runner.

Byzantium Endures

In 330 CE Constantine dedicated a new capital on the Bosporus, on the site of the old Greek town of Byzantium: Constantinople. It commanded the sea lane between the Black Sea and the Mediterranean and the land bridge between Europe and Asia. When the last western emperor, Romulus Augustulus, was deposed in 476, the Roman Empire did not end. Its eastern half, ruled from Constantinople, carried on for nearly another thousand years.

Its people never called themselves Byzantines. They were Romaioi, Romans, though they spoke Greek and worshipped as Christians. Their most ambitious ruler, Justinian, who reigned from 527 to 565, reconquered North Africa and Italy for a time and ordered jurists to gather centuries of Roman law into a single code, the Corpus Juris Civilis, completed by 534. Rediscovered in Bologna in the late eleventh century, it still underpins the civil law of much of Europe and Latin America. In 537 he dedicated the Hagia Sophia, which remained the largest church in Christendom for nearly a thousand years.

Survival was the real achievement. In the 630s and 640s the empire lost Syria, Palestine and Egypt to the Arab armies, then fought off sieges of the capital in the 670s and in 717 to 718, helped by Greek fire, an incendiary liquid whose exact recipe is still unknown. The city's best defence was its land walls, completed under Theodosius II in 413: a moat, an outer wall and an inner wall about 12 metres high with 96 towers, running about 6 kilometres from the Sea of Marmara to the Golden Horn. For over a thousand years, no army took them by storm.

Byzantium also drew half of Europe's spiritual map. The missionary brothers Cyril and Methodius took Christianity to the Slavs in the 860s, and their followers created the Cyrillic alphabet. In 988 Prince Vladimir of Kyiv was baptised, binding the Rus to Orthodox Christianity. The schism of 1054 formalised the split between the churches of Rome and Constantinople.

Did you know? The name "Byzantine Empire" was popularised by the German scholar Hieronymus Wolf in 1557, more than a century after the empire had ceased to exist.

The deepest wound came from fellow Christians. In 1204 the Fourth Crusade, diverted by its debts to Venice, sacked Constantinople and carried off its treasures, including the bronze horses now at St Mark's Basilica. The empire was restored in 1261 but never regained its strength. On 29 May 1453 the Ottoman sultan Mehmed II, after a siege of about seven weeks using huge bronze cannon, took the city. The last emperor, Constantine XI, died in the fighting.

Greek scholars who fled west carried manuscripts of Plato and Homer to Italy, feeding the Renaissance. The empire fell, but it had kept the inheritance safe until the other half of Europe was ready to use it.

The Buddhist Road

Sometime around the fifth century BCE, in the Ganges plain of north-east India, a prince named Siddhartha Gautama gave up a comfortable life to seek an end to suffering. Seated under a tree at Bodh Gaya, tradition says, he reached enlightenment and became the Buddha, "the awakened one". His exact dates are debated. His teaching was practical: suffering arises from craving, and a disciplined path of ethics, meditation and wisdom can end it. He wrote nothing down, founded an order of monks and nuns, the sangha, and spent decades walking and teaching.

The faith's first great patron was an emperor who had seen too much war. Around 261 BCE the Mauryan ruler Ashoka conquered Kalinga on India's east coast, at a cost his own inscriptions put at 100,000 killed. Shaken, he turned to the dhamma, carving edicts on rocks and pillars across his realm and sending envoys abroad. By tradition his son Mahinda brought Buddhism to Sri Lanka around 250 BCE, and the island later became the fountainhead of the Theravada school in South-East Asia.

From there the faith moved with trade rather than troops. In Gandhara, in today's Pakistan and Afghanistan, under the Kushan kings, sculptors influenced by Greek art made some of the first images of the Buddha in human form. Monks and merchants travelled together along the Silk Roads, monasteries doubled as hostels and lenders, and oasis towns such as Dunhuang filled with painted caves. By the second century CE translators such as An Shigao were at work in Luoyang, and in 401 the monk Kumarajiva, from the oasis kingdom of Kucha, arrived in Chang'an, where his translations shaped Chinese Buddhism for centuries.

Buddhism survived by adapting. In China it borrowed Daoist words to explain itself, and the meditative Chan school later became Zen in Japan. It reached Korea from China in 372 CE and Japan from the Korean kingdom of Baekje in 538 or 552. In Tibet, kings of the seventh and eighth centuries invited teachers from India, and Samye, the first monastery, was founded around 779. Pilgrims travelled the other way: the Chinese monk Xuanzang walked to India in 629, studied at the great monastic university of Nalanda, and came home in 645 with hundreds of texts.

Did you know? The world's oldest dated printed book is Buddhist: a copy of the Diamond Sutra from the caves of Dunhuang, printed in 868 CE and now in the British Library.

Ironically, the faith faded in its homeland, declining in India after the twelfth century as royal patronage shifted and monasteries such as Nalanda were sacked. Its centre of gravity moved east, where it shaped art, printing, medicine and politics from Sri Lanka to Japan.

No Buddhist empire ever spanned Asia. Ashoka gave the faith a push, but monks, translators and caravans carried it the rest of the way. A continent was converted on foot.

Charlemagne's Europe

On Christmas Day in the year 800, in St Peter's Basilica in Rome, Pope Leo III placed a crown on the head of Charles, king of the Franks, and the congregation acclaimed him emperor of the Romans. More than three centuries after the last western emperor had been deposed, the title had a holder again. Charles the Great, Charlemagne, had been made heir to Rome by a bishop of the Church.

He had won the power long before the crown. King from 768, and sole ruler after his brother Carloman died in 771, he went to war almost every year. He took the Lombard kingdom of Italy in 774, absorbed Bavaria in 788 and broke the Avar khaganate in the 790s, seizing its fabled treasure. His wars against the pagan Saxons lasted some thirty years and included forced baptisms and, according to the royal annals, the execution of 4,500 prisoners at Verden in 782. A raid into Spain in 778 ended in an ambush at Roncevaux, later reimagined as the Song of Roland. By 800 his realm stretched from the Pyrenees to the Elbe and from the North Sea to central Italy.

The coronation suited both men. Leo, attacked in the streets of Rome by his enemies the year before, needed a protector. Charles gained a dignity to match Constantinople's, where the empress Irene then ruled, and western churchmen argued that a woman could not hold the imperial throne. His biographer Einhard claims Charles said he would not have entered the church that day had he known the pope's plan; historians still debate how sincere that was.

Ruling such a sprawl with few roads, no bureaucracy and little literacy took improvisation. Several hundred counts governed districts in his name, with margraves guarding the frontier marches. Paired inspectors, the missi dominici, usually a lay noble and a churchman, toured to check on them, and written decrees called capitularies set out the rules. At his palace in Aachen the English scholar Alcuin of York led a revival of learning. Monks copied classical texts in a clear new script, Carolingian minuscule, ancestor of the lower-case letters on this page, and the oldest surviving copies of many Roman authors were made in Carolingian monasteries.

Did you know? Charlemagne's coinage reform set 240 silver pennies to the pound, a reckoning Britain kept until decimalisation in 1971.

His world reached well beyond Europe. The Abbasid caliph Harun al-Rashid sent him an elephant named Abul-Abbas, which arrived at Aachen in 802. But the unity was personal. After his son Louis the Pious, the grandsons split the empire at the Treaty of Verdun in 843 into western, middle and eastern kingdoms, rough sketches of France, the Low Countries and Germany.

Yet the idea endured: a Christian Europe, joined by faith, Latin and the memory of Rome. It was revived in 962 as what became the Holy Roman Empire, and it echoes in every later dream of European union. Empires fade; a good idea of one does not.

Faith Builds Wonders

Every age builds what it believes in. For the medieval world, from Ethiopia to Java, that meant houses of God: churches, mosques, temples and monasteries that soaked up more labour, money and skill than any other undertaking of the time. They were the era's supercomputers of belief, pooling the resources of whole societies across generations to answer one question: what is worth building for eternity?

The paymasters were many. Christian Europe funded churches through the tithe, a tenth of produce owed to the Church, as well as royal grants, bishops' estates and the offerings of pilgrims who came to see relics. In the Islamic world the waqf, a perpetual charitable endowment, could keep a mosque, school or hospital running for centuries. At Angkor, Khmer kings tied the rice economy of a whole region to temple estates. And contrary to a popular image, most great buildings were raised not by slaves or unpaid peasants but by paid, highly skilled masons, carpenters and glaziers who moved from site to site.

The results still astonish. In Constantinople, Justinian's Hagia Sophia went up in under six years, from 532 to 537, crowned by a dome about 31 metres across. In Córdoba, Abd al-Rahman I began the Great Mosque in 785, and his successors enlarged it for two centuries into a forest of hundreds of columns and double-tiered arches. In central Java, the Shailendra dynasty built Borobudur around 800, a stepped mountain of some two million stone blocks carrying 2,672 relief panels and 504 Buddha statues. In Cambodia, Suryavarman II raised Angkor Wat in the early twelfth century, dedicated to Vishnu, within a moat some 190 metres wide.

Then came the cathedrals. In the 1140s Abbot Suger rebuilt the choir of Saint-Denis near Paris with pointed arches, ribbed vaults and walls of coloured glass, launching the Gothic style. Flying buttresses let walls rise higher and thinner. Chartres was largely rebuilt in about a quarter of a century after a fire in 1194, and still keeps most of its original stained glass. Others took far longer: Cologne Cathedral, begun in 1248, was finished only in 1880.

Did you know? When Cologne Cathedral was completed in 1880, its twin spires of about 157 metres made it the tallest building in the world, until the Washington Monument overtook it in 1884.

Faith built in every material. In Ethiopia, King Lalibela's craftsmen carved eleven churches downwards into solid rock around 1200. At Djenné, in the lands of the Mali Empire, the townspeople replaster their great mud-brick mosque together in an annual festival.

These buildings were also economies, schools and statements of power. They trained craftsmen, spread techniques and drew pilgrims who paid for food, lodging and souvenirs. A cathedral town lived off its cathedral much as a modern town lives off its factory, and the work could outlast every person who began it.

Stone was how a society said what mattered most.

The Crusades Collide

In November 1095, at Clermont in central France, Pope Urban II preached a sermon that would echo for two centuries. The Byzantine emperor Alexios I Komnenos had asked for western soldiers to help against the Seljuk Turks, who had crushed a Byzantine army at Manzikert in 1071 and overrun much of Anatolia. Urban offered something far bigger: an armed pilgrimage to free Jerusalem, with the remission of sins for all who took the cross. The crowd, by later accounts, answered with the cry Deus vult, "God wills it".

The response stunned everyone. Tens of thousands set out. Some bands began by massacring Jewish communities in the Rhineland in 1096. The main armies of the First Crusade passed through Constantinople, took Antioch in 1098 after a brutal siege, and stormed Jerusalem on 15 July 1099, killing much of its population. Four crusader states followed, Edessa, Antioch, Tripoli and the Kingdom of Jerusalem, a thin strip of Latin rule along the Levant coast.

The Muslim world was divided when the crusaders arrived, and slowly reunited against them. Edessa fell in 1144, provoking a failed Second Crusade. Then the Kurdish sultan Saladin, ruler of Egypt and Syria, destroyed the crusader army at Hattin in 1187 and retook Jerusalem, sparing most of its inhabitants. The Third Crusade, led by Richard I of England and Philip II of France, regained Acre but not the Holy City, and ended in a truce in 1192. The Fourth Crusade never reached the Holy Land at all: in 1204 it sacked Christian Constantinople instead. Emperor Frederick II recovered Jerusalem by treaty in 1229, without a battle, only for it to be lost again in 1244. In 1291 the Mamluks of Egypt took Acre, the last great crusader stronghold.

Did you know? Arabic chroniclers seldom used any word for "crusade"; they called the invaders simply al-Faranj, "the Franks", whatever country they came from.

The human cost cannot be counted precisely. Estimates vary widely, but deaths over two centuries ran at least into the hundreds of thousands, civilians of every faith among them. Jerusalem, the prize, ended where it began, in Muslim hands. For many Muslim rulers the Mongols, who sacked Baghdad in 1258, were the far graver danger.

Yet the wars changed the Mediterranean. Venice, Genoa and Pisa won trading quarters in Levantine ports and grew rich shipping pilgrims, soldiers and goods. Europeans acquired a taste for sugar, spices, cotton and silk, and military orders such as the Templars and Hospitallers built networks for moving money that resembled early banking. The crusading idea itself spread, turned against Muslims in Iberia, pagans around the Baltic and heretics in southern France, while the bitterness of 1204 deepened the split between Latin and Orthodox Christianity.

In the West the crusades became a legend, endlessly retold; in the Muslim world they were long remembered as one frontier war among many. The crusaders set out to win a city. They ended up reconnecting a sea.

Belief Moves History

Look at almost any medieval map and you are looking at a map of faith. Around 1300 the makers of the Hereford Mappa Mundi placed Jerusalem at the centre of the world and Paradise at its top. Muslims everywhere turned towards Mecca in prayer five times a day, and the Hajj drew pilgrims across deserts and oceans. In 1324 Mansa Musa, ruler of the Mali Empire, made that pilgrimage with so much gold that, according to the Cairo writer al-Umari, its value in Egypt fell for years. Half a century later the Catalan Atlas of 1375 painted him on his throne, holding a golden nugget.

For roughly a thousand years, from the fall of the western Roman Empire to the age of print, religion was arguably the deepest organising force in human society. It set the clock and the calendar: monastery bells divided the day, Christians counted years anno Domini, a system popularised by the English monk Bede, and Muslims counted from the Hijra. It wrote much of the law. Church courts judged marriages and wills across Latin Europe, Muslim jurists built the schools of sharia that governed contracts and families from Morocco to India, and the Buddhist monastic code, the vinaya, ordered life in thousands of monasteries.

It ran the schools. Cathedral schools grew into Europe's first universities at Bologna, Paris and Oxford. The madrasa spread across the Islamic world, and the mosque of al-Qarawiyyin in Fez, later a famous centre of learning, traces its founding in 859 to a woman, Fatima al-Fihri. Nalanda in India trained monks from across Asia for centuries. And it moved money: the tithe, the waqf and great monastic and temple estates channelled a large share of every economy into buildings, charity and learning.

Rulers knew where legitimacy lay. Charlemagne took his crown from a pope; caliphs ruled as successors of the Prophet; Tibetan kings promoted Buddhism; Aztec rulers justified war as feeding the gods. When the emperor Henry IV defied Pope Gregory VII, he was excommunicated and in 1077 stood in the snow at Canossa, waiting to be forgiven.

Did you know? The Hereford Mappa Mundi, made around 1300, is the largest medieval map known to survive, about 1.6 metres tall, and is drawn with east, not north, at the top.

The claim has limits. Religion and state were rarely separate, so faith often served power as much as power served faith. Song China ran a vast bureaucracy chosen by examination in Confucian classics, a tradition most scholars treat as a philosophy rather than a church. Wars fought in the name of God were often about land and loot.

Still, the pattern is hard to miss. The largest buildings, the biggest landowners, the widest networks of literacy and the most powerful ideas about life and death belonged, nearly everywhere, to faiths. When printing, science and new kinds of state began to challenge that dominance from the fifteenth century, they were taking on the heaviest weight in history.

For a millennium, belief drew the map.

The Silk Roads

For some fifteen centuries a loose web of caravan tracks linked the cities of China to the shores of the Mediterranean. We call it the Silk Road, but it was never a single road. It was a braid of routes across deserts, mountain passes and oasis towns, shifting with wars, water and fashion. Silk went west; horses, glass, silver, wine and ideas came east.

The opening is usually dated to the Han dynasty. Around 138 BCE Emperor Wu sent the envoy Zhang Qian west to find allies against the Xiongnu nomads. He was captured, held for about ten years, escaped and came home with reports of the "heavenly horses" of Ferghana and the rich markets of Bactria. Within decades Han garrisons guarded the Gansu corridor, and caravans from the capital, Chang'an, passed Dunhuang before skirting the Taklamakan Desert by way of oases such as Kashgar.

Almost no one made the whole journey. A bolt of silk changed hands again and again. Chinese producers sold to merchants in the oases; Sogdian traders from Samarkand and Bukhara, the great middlemen of the first millennium, carried it across Central Asia; Parthian and later Sasanian Persians controlled the stretch to Mesopotamia and guarded their profits jealously; Syrian and Greek merchants took it on to Antioch, Tyre and Rome. Each hand added a margin. When the Han general Ban Chao sent the envoy Gan Ying towards Rome in 97 CE, he reached the edge of the Parthian world and was talked out of the final sea crossing, reportedly by Parthians with every reason to keep the two empires apart.

Rome paid dearly. Pliny the Elder complained that India, China and Arabia drained the empire of 100 million sesterces a year, and moralists grumbled that silk was so sheer it left Roman women barely clothed. China kept the secret of sericulture until, according to the Byzantine historian Procopius, monks smuggled silkworm eggs to Constantinople for Emperor Justinian around 552 CE.

Goods were only part of the cargo. Buddhism travelled from India to China along these routes from around the first century CE, and the cave temples at Dunhuang still preserve its art, along with the Diamond Sutra of 868, the oldest dated printed book. Nestorian Christians, Manichaeans and later Muslims followed the same tracks. So, in time, did disease: the roads that carried silk would one day carry plague.

Did you know? The name "Silk Road" is not ancient at all: the German geographer Ferdinand von Richthofen coined Seidenstraße in 1877, and none of the merchants who used the routes ever called them that.

The Silk Roads were less a highway than a relay race, with silver as the baton. Silk went one way, silver the other, and ideas went everywhere.

The Mongol Peace

In 1206 a kurultai, a great assembly of steppe chiefs, proclaimed the Mongol leader Temüjin as Chinggis Khan. Within seventy years his armies, and those of his sons and grandsons, had built the largest contiguous land empire in history: by one common estimate around 24 million square kilometres, from Korea to the plains of Hungary, which Mongol armies ravaged in 1241, and from Siberia to the Persian Gulf.

The conquest was terrible. Cities that resisted were often destroyed and their people killed: Merv, Nishapur and Urgench in Central Asia in the 1220s, and Baghdad in 1258, when the last Abbasid caliph was put to death. Contemporary chroniclers gave figures that are surely inflated, and modern estimates of the total dead vary enormously, from several million to tens of millions. Terror was also a strategy. A town that heard what had happened to its neighbour usually opened its gates.

Yet the same empire created what historians call the Pax Mongolica, a century in which a merchant could cross Eurasia under the protection of one ruling family. The yam, a relay network of post stations with fresh horses, carried officials and messages across the empire, and a paiza, a tablet of gold, silver or wood, worked like a passport that commanded food and mounts. Decimal army units of 10, 100, 1,000 and 10,000 men, censuses for taxation and resident governors called darughachi held the system together. The khans favoured merchants, invested in trading partnerships known as ortogh, and generally left religions alone, exempting clergy from taxes.

Travellers took advantage. William of Rubruck, a Flemish friar, reached the capital, Karakorum, in 1253–54. The Venetian Marco Polo spent years in the service of Kublai Khan. Rabban Bar Sauma, a Nestorian monk born near modern Beijing, travelled the other way and met the pope and the king of France in 1287–88. Persian astronomers worked in China, Chinese physicians in Persia, and Rashid al-Din, a vizier of the Mongol Ilkhans, compiled a history of the whole known world.

The empire did not stay united. After the death of the Great Khan Möngke in 1259 it split into four khanates: the Yuan dynasty in China under Kublai, the Chagatai Khanate in Central Asia, the Ilkhanate in Persia and the Golden Horde on the Russian steppe. They often fought each other, but the caravans kept moving until the Yuan fell in 1368. The roads also carried something deadlier: plague, which travelled west in the 1340s along routes the Mongols had made busy.

Did you know? In 1254 the Great Khan Möngke staged a formal debate at Karakorum between Christian, Muslim and Buddhist scholars; according to William of Rubruck, who took part, it ended with everyone drinking heavily.

The Mongols made the world smaller, and they did it with the sword.

Mansa Musa's Gold

In 1324 a caravan passed through Cairo on its way to Mecca that the city talked about for a generation. At its head was Mansa Musa, ruler of the Mali Empire, travelling with thousands of followers, tens of thousands in some accounts, and, by later reports, around a hundred camel-loads of gold. He gave it away so freely, to officials, to the poor and to merchants, that the scholar al-Umari, writing in Cairo about twelve years later, reported that the value of gold there had fallen and still had not recovered.

The gold had a source. Mali, founded by Sundiata Keita after his victory at Kirina around 1235, controlled or taxed the goldfields of Bambuk and Bure near the upper Senegal and Niger rivers. For centuries West African gold had crossed the Sahara by camel, traded north for salt from desert mines such as Taghaza, and for copper, cloth and horses. Historians agree that a large share of the gold circulating in the medieval Mediterranean world, from Egyptian dinars to the first gold florins of Florence in 1252, came from West Africa.

Mali was a Muslim state with a royal court, scribes, governors and links across the Islamic world. Its cities, among them Djenné, Gao and Timbuktu, lined the Niger, the river highway of the Sahel. When Ibn Battuta visited in 1352–53 he grumbled about the food and the stinginess of his gifts, but praised the country's security: travellers, he wrote, had no fear of thieves or violence.

The pilgrimage was diplomacy as much as devotion. Musa came home with scholars and with Abu Ishaq al-Sahili, a poet and architect from al-Andalus, who is credited with building the Djinguereber Mosque in Timbuktu around 1327. He also came home short of cash. Al-Umari records that he had to borrow from Cairo merchants for the journey back, an unusual problem for a man so rich. Generosity on that scale had a price.

Europe noticed. In 1375 the Catalan Atlas, made in Majorca and attributed to the Jewish cartographer Abraham Cresques, showed a crowned African king on a throne holding up a golden nugget, described as the richest and noblest lord in all the land. Within a century, Portuguese ships were edging down the African coast, looking for a way to reach that gold without paying the Saharan middlemen.

Did you know? Mansa Musa is often called the richest person who ever lived, but his fortune cannot be measured: modern rankings that put a dollar figure on it are guesswork.

Medieval West Africa was not on the margins of the world economy. It was underwriting it.

The Indian Ocean

Long before Portuguese ships rounded Africa, the Indian Ocean was the busiest maritime trading world on Earth. Its engine was the monsoon, a seasonal reversal of the winds. From roughly April to September the south-west monsoon blows from Africa and Arabia towards India; from about November to March the north-east monsoon blows back. A ship that caught one wind out and the other home could make a round trip in a year, as regularly as a timetable.

Sailors around the ocean had used the winds for a very long time, and Greek merchants in Roman Egypt learned the trick in the first century BCE; tradition credits a navigator called Hippalus. The Periplus of the Erythraean Sea, a merchant's handbook of the first century CE, lists ports from the Red Sea to the Ganges and what to buy and sell in each. By the ninth century Arab and Persian ships sailed all the way to China: the Belitung wreck, an Arab-style ship found off Indonesia, sank around 830 with some 60,000 objects aboard, most of them Chinese ceramics.

The network worked as a relay of linked seas. Swahili city-states on the East African coast, among them Kilwa, Mombasa and Mogadishu, exported gold from the Zimbabwe plateau through Sofala, along with ivory and timber. Aden and Hormuz handled the Arabian end; Cambay in Gujarat sold cotton cloth across the ocean; Calicut on the Malabar coast was the pepper capital; Malacca, founded around 1400, controlled the strait into the South China Sea; and Quanzhou in China, which Marco Polo and Ibn Battuta both called Zaitun, was among the largest ports in the world. Many ships were dhows, their planks sewn together with coconut-fibre cord rather than nailed.

Islam spread along these routes with merchants rather than armies, reaching the Swahili coast, the Maldives and parts of Sumatra and Java. Between 1405 and 1433 the Ming admiral Zheng He, a Muslim eunuch from Yunnan, led seven state fleets across the ocean, the first reportedly carrying nearly 28,000 men, as far as Hormuz, Aden and Malindi. Then the Ming court ended the voyages, and private Chinese and Asian merchants carried on the trade.

When Vasco da Gama reached Calicut in 1498, he arrived as a late, small and rather poor newcomer. His fleet had needed a local pilot from Malindi to cross the ocean; a popular story names him as the famous navigator Ibn Majid, but historians doubt it. The gifts da Gama offered the ruler of Calicut were mocked as cheap. What the Portuguese brought was not better goods but heavier guns, and a plan to control the sea by force.

Did you know? In 1414 a giraffe from East Africa arrived at the Ming court, brought by envoys from Bengal; Chinese officials greeted it as a qilin, a mythical beast of good omen.

Europe did not discover the Indian Ocean. It gatecrashed it.

The Black Death

In the 1340s a bacterium, Yersinia pestis, moved out of Central Asia along the trade routes the Mongols had made busy. Ancient DNA from graves near Lake Issyk-Kul in modern Kyrgyzstan, dated 1338–39, has identified a strain that probably began the pandemic. By 1346 it had reached the Black Sea, where an army of the Golden Horde besieging the Genoese port of Caffa in Crimea was struck by plague. The story that the besiegers catapulted infected corpses over the walls comes from a single Italian writer, Gabriele de' Mussi, and may be exaggerated. Either way, Genoese galleys carried the disease to Messina in Sicily in October 1347.

From there it raced along shipping lanes and roads. Alexandria and Cairo were struck in 1347–48; Florence, Paris and southern England in 1348; Norway and Scotland by 1349; Moscow by around 1352. It spread mainly through fleas carried by rats and perhaps by people. In its bubonic form it raised swollen lymph nodes called buboes; in its pneumonic form it passed from person to person through the air and was almost always fatal. Physicians blamed corrupt air and the alignment of the planets.

The death toll was staggering. Estimates for Europe range from about a third to more than half the population, perhaps 25 to 50 million people, between 1347 and 1351; Egypt and Syria suffered on a similar scale. Whole villages were abandoned. Fear found scapegoats. Jewish communities were accused of poisoning wells and massacred in scores of towns, including Strasbourg in February 1349, despite papal bulls from Clement VI pointing out that Jews were dying of plague too.

Then came the economic aftershock. With land plentiful and labour scarce, survivors could demand more. In England the crown tried to freeze wages with the Ordinance of Labourers in 1349 and the Statute of Labourers in 1351, with little lasting success. Peasants and workers rose up: the Jacquerie in France in 1358, the Ciompi wool workers of Florence in 1378, and the English Peasants' Revolt of 1381. Over the following century serfdom faded across much of western Europe, wages rose and diets improved. In eastern Europe, by contrast, lords later tightened their grip on the peasantry, a reminder that catastrophe follows no single script.

The plague did not leave. It returned every decade or so for more than three centuries, reaching London as late as 1665 and Marseille in 1720. Some historians link the labour shortage to later changes, from new technology to Atlantic ventures, though such long chains of cause are still debated.

Did you know? The first known quarantine law was passed by the port of Ragusa, now Dubrovnik, in 1377: arrivals from plague areas had to wait 30 days. Later 40-day waits gave English the word quarantine, from the Italian quaranta.

The Black Death killed millions, and made the survivors expensive.

Cahokia and the Maya

Around 1100 CE a traveller on the Mississippi near modern St Louis would have seen an earthen mound rising some 30 metres above the floodplain, crowned by a great timber building. This was Monks Mound, the centre of Cahokia, the largest city in North America north of Mexico before the modern era. At its height, between about 1050 and 1150, Cahokia and its surroundings held perhaps 10,000 to 20,000 people, though estimates vary.

Cahokia was the heart of the Mississippian culture, and it was built on maize. Its people raised more than a hundred earthen mounds, levelled a vast central plaza and set up circles of wooden posts, nicknamed "Woodhenge" by archaeologists, that appear to have marked sunrises at the solstices and equinoxes. A burial mound known as Mound 72 held an elite man laid on a platform of thousands of shell beads, alongside the remains of dozens of sacrificed people. By around 1350 the city was largely empty, for reasons still debated: floods, drought, deforestation, political strife or all of them.

Far to the south the Maya had been building cities for well over a thousand years. In the Classic period, roughly 250 to 900 CE, dozens of rival kingdoms such as Tikal, Calakmul, Palenque and Copán filled the lowland forests of what are now Guatemala, Mexico, Belize and Honduras. Temple IV at Tikal, finished around 741, rises about 65 metres. Maya scribes wrote in a full script of several hundred signs, recorded the deeds of kings on stone stelae, and counted time with the Long Count calendar, which used a sign for zero, a concept Mesoamericans reached independently. Astronomers tracked the cycles of Venus with remarkable precision, as the Dresden Codex shows.

In the ninth century many southern cities were abandoned, in what is called the Classic Maya collapse, most likely driven by drought, warfare and exhausted farmland. But the Maya did not vanish. Northern cities such as Chichén Itzá flourished afterwards, the last independent Maya kingdom held out against Spain until 1697, and millions of Maya people live in the region today, many still speaking Mayan languages.

None of this was borrowed. Apart from a brief Norse landing in Newfoundland around 1000 CE, the Americas had no contact with Afro-Eurasia. Yet their peoples domesticated maize from a wild grass called teosinte about 9,000 years ago, and went on to build cities, calendars, writing systems and monumental pyramids of their own. Pyramids rose on both sides of the Atlantic for a simpler reason than lost continents or ancient visitors: a heap that narrows towards the top is the most stable way to build high with earth and stone.

Did you know? The base of Monks Mound, roughly 291 by 236 metres, covers more ground than the Great Pyramid of Giza.

Civilisation was invented more than once.

Paper and Powder

In 1620 the English philosopher Francis Bacon named three inventions that had "changed the whole face and state of things throughout the world": printing, gunpowder and the magnet, by which he meant the compass. He did not know where they came from. All three, along with the paper that printing depended on, were first developed in China, and reached Europe slowly, by way of Central Asia and the Islamic world.

Paper came first. Chinese records credit the court official Cai Lun with presenting an improved paper to the emperor in 105 CE, made from bark, hemp, rags and old fishing nets, though archaeologists have found older paper. Papermaking reached Samarkand by the eighth century. A popular story says Chinese prisoners captured at the Battle of Talas in 751 taught it there, but this is probably a later legend. Baghdad had paper mills by around 800, and the Abbasid bureaucracy, scholars and booksellers ran on it. Muslim Spain was making paper at Xàtiva by the twelfth century, and Italy at Fabriano by the 1270s.

Printing followed. Chinese printers carved whole pages into wooden blocks; the Diamond Sutra, found at Dunhuang and dated 868, is the oldest surviving dated printed book. In the 1040s a craftsman named Bi Sheng made movable type from baked clay, and in 1377 Korean monks printed the Jikji, the oldest surviving book made with movable metal type. Whether Johannes Gutenberg, printing in Mainz around 1450, knew of Asian methods is unknown. There is no evidence that he did, and his press, oil-based ink and type-casting mould were his own.

The compass began as a curiosity, a magnetised spoon or needle used in divination and geomancy. By around 1117 a Chinese writer recorded sailors using it to steer in cloudy weather, and in Europe the English scholar Alexander Neckam described one around 1190. Gunpowder was discovered by Chinese alchemists searching for elixirs of life; the military manual Wujing Zongyao of 1044 gives the earliest known formulas. Fire lances, bombs and early guns followed, and the Mongol wars helped spread the technology west. Roger Bacon recorded a recipe in England in 1267, and a cannon appears in an English manuscript of 1326.

The irony is sharp. Paper and printing fed Europe's Reformation and scientific revolution; the compass guided its ships across the oceans; and gunpowder armed the fleets and armies that built its empires, eventually reaching China itself. The "Four Great Inventions" is a modern label, and China invented far more than four things, from the crossbow trigger to the sternpost rudder, but the pattern is plain.

Did you know? The Chinese scholar Shen Kuo described magnetic declination, the gap between magnetic and true north, in 1088, about four centuries before Columbus noticed it on his Atlantic crossing.

The modern West was built with borrowed tools.

Timbuktu's Libraries

Timbuktu began, according to local tradition, around 1100 as a seasonal camp of Tuareg herders near the great bend of the Niger River, where the Sahara meets the river. Its position made its fortune. Camel caravans from North Africa brought salt, cloth, books and horses; boats on the Niger brought gold, grain, kola nuts and enslaved people from the south. By the fourteenth century, when it came under the Mali Empire, Timbuktu was one of the great markets of West Africa.

Wealth bought learning. After Mansa Musa's return from Mecca the Djinguereber Mosque was built around 1327, and with the Sankore and Sidi Yahya mosques it became a centre of teaching. There was no single university in the modern sense, despite the popular phrase "University of Sankore". Instead, families of scholars taught students in mosques and homes, granting a licence called an ijaza to those who had mastered a text. Under the Songhai Empire, which took the city in 1468, and especially under Askia Muhammad from 1493, Timbuktu reached its height, drawing students from across West Africa and beyond.

Books were the city's prize commodity. The traveller Leo Africanus, who visited in the early sixteenth century, wrote that manuscripts brought from North Africa sold for more profit than any other merchandise. Families built private libraries on Maliki law, theology, grammar, astronomy, mathematics, medicine, poetry and commerce. Most were written in Arabic, but some were in African languages such as Songhai and Fulfulde using Arabic script, a practice called Ajami. The most celebrated scholar, Ahmad Baba (1556–1627), wrote dozens of works and reportedly said that his own library of 1,600 volumes was one of the smallest in his family.

Golden ages end. In 1591 a Moroccan army armed with firearms crossed the Sahara and defeated Songhai at Tondibi; Ahmad Baba was deported in chains to Marrakesh. Trade routes shifted towards the Atlantic coast, where European ships now called, and Timbuktu slowly declined. But the manuscripts survived, kept in family chests, sometimes buried or walled up, through centuries of drought, conquest and colonial rule.

In 2012 armed jihadist groups occupied Timbuktu and destroyed the tombs of local saints. As they retreated in January 2013 they set fire to manuscripts at the Ahmed Baba Institute, burning around 4,000. Most of the collections had already gone. Librarians led by Abdel Kader Haidara had quietly smuggled some 350,000 manuscripts south to Bamako, packed in metal trunks and moved by road and river. Estimates of the total held in the Timbuktu region run into the hundreds of thousands, and many are still being catalogued and digitised.

Did you know? Many Timbuktu manuscripts are written on paper made in Italy: watermarks such as Venice's "three crescents" show how far the medieval book trade reached.

Africa's past was written down. The world simply had not been reading it.

Ideas Ride With Goods

Every caravan and every ship carried a second, invisible cargo. Merchants brought their gods, their numbers, their recipes and their microbes, and they spent months in foreign ports where they married, prayed, argued and swapped stories. Over the centuries this traffic in ideas changed the world more deeply than the silk or pepper that paid for it.

Religions travelled this way. Buddhism left India with merchants and monks along the Silk Roads and reached China by the first century CE; in the seventh century the Chinese monk Xuanzang walked to India and back, a journey of some sixteen years, returning with hundreds of texts. Islam reached West Africa with trans-Saharan traders, and the coasts of East Africa, India and Southeast Asia with sailors and merchants rather than armies. By the fifteenth century the ruler of Malacca had converted, and the faith spread through the islands that now form Indonesia, today the country with the most Muslims in the world.

So did numbers. The decimal place-value system with a zero developed in India, and the mathematician Brahmagupta set out rules for calculating with zero in 628. In Baghdad around 825, al-Khwarizmi wrote a treatise on Indian numerals; his name, Latinised, gives us the word algorithm. A merchant's son, Leonardo of Pisa, known later as Fibonacci, learned the numerals as a boy in the North African port of Bugia, now Béjaïa in Algeria, where his father worked for Pisan merchants. His Liber Abaci of 1202 promoted them in Europe largely as a tool for bookkeeping, currency conversion and trade.

Crops and techniques followed the same paths. Sugar cane, cotton, rice, citrus fruits and aubergines spread west across the Islamic world to the Mediterranean, alongside irrigation methods and paper. Sugar in particular would later drive the plantation economies of the Atlantic, with terrible human consequences.

Diseases travelled too. The Plague of Justinian, which struck Constantinople in 541, seems to have arrived on grain ships from Egypt; the Black Death of the 1340s rode Mongol-era caravans and Genoese galleys. Smallpox and measles had circulated between Asia, Africa and Europe for centuries, giving Old World populations a measure of inherited and acquired immunity that the peoples of the Americas would tragically lack.

The pattern is a cycle. Trade moves goods; goods carry people and ideas; new ideas change how people farm, count, worship and fight; and those changes create new demand and new trade. Isolated societies, by contrast, have usually had to invent everything themselves, a slower road.

Did you know? The word "zero" comes from the Arabic sifr, "empty", a translation of the Sanskrit shunya; the same Arabic word also gave English "cipher".

Connection has always been history's accelerant, for better and for worse.

The Connected Old World

A map of the world in 1400, drawn by an honest observer, would not have put Europe at its centre. The middle of the picture belonged to a belt of great cities: Hangzhou and Quanzhou in China, Delhi and Calicut in India, Tabriz, Damascus and Cairo in the Islamic heartland. Venice, Genoa and Bruges sat at the western end of a web whose richest strands lay far to the east.

The sociologist Janet Abu-Lughod argued in Before European Hegemony (1989) that between about 1250 and 1350 Afro-Eurasia already formed a single world system of eight interlocking trading circuits. They ran from the fairs of Champagne and the Mediterranean, through the Middle East, the Arabian Sea, the Bay of Bengal and the South China Sea, to the Mongol-ruled steppe and China. No single power ran the system. Goods moved from circuit to circuit, handed on at hubs such as Cairo, Hormuz, Calicut and Malacca, as earlier chapters followed silk, gold and pepper doing.

Two engines drove the web. China, under the Song and then the Yuan and Ming dynasties, was by most modern estimates the world's largest economy, with the biggest population, paper money, a vast iron industry and porcelain prized from Kilwa to Cairo. The Islamic world, stretching from Morocco to the islands of Southeast Asia, supplied much of the connective tissue: a shared language of scholarship and law, commercial partnerships, credit and cities where a merchant from Fez could find a mosque, a judge and a familiar contract.

No life shows the scale better than that of Ibn Battuta, a legal scholar from Tangier. Between 1325 and 1354 he travelled, by common reckoning, around 117,000 kilometres, through North Africa, Arabia, Persia, the lands of the Golden Horde, India, the Maldives, Southeast Asia, China (though some scholars doubt parts of that account) and finally Mali. Almost everywhere he went he found fellow Muslims who gave him hospitality, and more than once a job as a judge.

The web had weak points. The Black Death tore through it in the 1340s; the Yuan dynasty fell in 1368; Timur's campaigns devastated Central Asia and northern India around 1400. Yet it recovered. The new Ming dynasty sent Zheng He's fleets across the Indian Ocean from 1405, and Venetian galleys still loaded spices at Alexandria and Beirut. When Europeans later sailed south around Africa and west across the Atlantic, they were trying to reach the wealth of Asia directly, not escaping from a backward world.

Did you know? Paper money circulated across China for centuries before Europe used it: Marco Polo marvelled that the Great Khan's mints turned mulberry bark into money that everyone accepted.

In 1400 the world was already global. Europe was simply on its rim.

The Renaissance Turn

Around 1400, Florence was a city of bankers and wool merchants, some 60,000 people living behind walls on the Arno. Across northern and central Italy, city-states such as Florence, Venice, Milan and Genoa had grown rich on cloth, on trade with the eastern Mediterranean, and on lending money to kings and popes. They had money to spend, rivals to outshine and the ruins of Rome on their doorstep. The result was the Renaissance, a revival of classical art and learning that put the human being, not only God, at the centre of the picture.

The revival began with books. The poet Petrarch (1304–1374) hunted through monastery libraries for lost Latin texts and in 1345 found a collection of Cicero's letters at Verona. He called the centuries since Rome's fall an age of darkness, a label that stuck far longer than it deserved. From 1397 the Byzantine scholar Manuel Chrysoloras taught Greek in Florence, and Greek manuscripts flowed west, carried by delegates to the Council of Florence in 1439 and by refugees after the Ottomans took Constantinople in 1453. Many of these texts had been copied and studied for centuries in Byzantium and the Islamic world, so the "rediscovery" was partly a homecoming.

Artists turned the new mood into something visible. Filippo Brunelleschi demonstrated the rules of linear perspective around 1415 and, between 1420 and 1436, raised the great dome of Florence Cathedral, still the largest brick dome ever built. Masaccio painted figures with weight and shadow; Donatello cast a bronze David, often called the first free-standing nude statue since antiquity. Leon Battista Alberti set out the theory in On Painting in 1435. A picture became a window onto a measured, human-scaled world.

Why did looking backwards feel like a beginning? Partly because it gave ambitious people a standard to compete against that was not set by the Church. Partly because the Black Death, which killed perhaps a third to a half of Europe's people from 1347, had shaken old certainties and concentrated wealth in fewer hands. And partly because self-governing, quarrelsome Italian cities needed citizens who could argue, write and persuade. Classical models supplied all three.

Did you know? The word "Renaissance" in its modern sense was popularised in the 19th century by Jules Michelet and Jacob Burckhardt; in 1550 Giorgio Vasari had written of a rinascita, a rebirth, of the arts.

The Renaissance was never a single event, and never only Italian. Flemish painters such as Jan van Eyck were making their own breakthroughs in oil paint in the 1430s, and the movement soon crossed the Alps to France, Germany and England. It fused with the printing press and fed directly into the religious upheaval of the next century. Patrons paid for it, scholars argued for it and painters made it visible. The past, carefully copied, became a tool for changing the present.

Gutenberg's Press

Before the 1450s, every book in Europe was copied by hand. A skilled scribe could spend months on a single Bible, and every copy introduced fresh errors. Books were valuable enough to be chained to library desks. Around 1450, in the Rhineland city of Mainz, a goldsmith named Johannes Gutenberg changed the arithmetic of knowledge.

Gutenberg did not invent printing, nor even movable type. Woodblock printing was centuries old in East Asia; in the 1040s the Chinese artisan Bi Sheng made movable type from baked clay, and Korean printers later cast type in metal. The Jikji, a Buddhist text printed in Korea in 1377, is the oldest surviving book made with movable metal type. But Chinese writing needs thousands of characters, which made movable type a hard bargain, while Latin needed only a few dozen letters plus punctuation and abbreviations.

What Gutenberg built was a system. A hand mould let workers cast identical letters, called sorts, from an alloy of lead, tin and antimony. Compositors set the sorts in lines, locked them into pages and inked them with an oil-based ink that clung to metal. A screw press, adapted from those used for wine and paper, pressed each sheet evenly. Then the type was broken up and reused. Around 1455 the workshop finished its great Latin Bible: about 180 copies, some on vellum and most on paper. Around 49 are known today, some of them incomplete.

The business side was less triumphant. Gutenberg had borrowed heavily from the financier Johann Fust, who sued him in 1455 and took over much of the equipment; Fust and Gutenberg's former assistant Peter Schöffer went on to print with great success. The technology itself could not be contained. Printers trained in Mainz carried it along the Rhine and over the Alps, and by 1500 presses had worked in some 250 European towns, with Venice the capital of the trade. There Aldus Manutius later pioneered small, portable editions of the classics in italic type. Estimates of the number of books printed in Europe before 1501 range from roughly 8 to 20 million copies, more than the continent's scribes had produced in centuries.

Did you know? Books printed in Europe before 1501 are called incunabula, from the Latin for "swaddling clothes", because they come from the cradle of printing.

Print standardised texts, so scholars in Paris and Kraków could cite the same page of the same edition. It made errors permanent, but corrections too. It created the first mass market for ideas and made authors, editions and title pages ordinary features of life. Within seventy years it would carry a German friar's protest across a continent. A machine for copying turned out to be a machine for change.

Leonardo's Mind

Leonardo da Vinci was born in 1452 near the Tuscan town of Vinci, the illegitimate son of a notary. That accident of birth kept him out of university and the learned professions; he never mastered Latin well and called himself an "unlettered man". Instead he trained in the Florentine workshop of Andrea del Verrocchio, where apprentices ground pigments, cast bronze and learned geometry alongside drawing. The workshop, not the lecture hall, shaped the most famous mind of the age.

Around 1482 he moved to Milan and offered his services to Duke Ludovico Sforza in a letter that listed bridges, siege engines and cannon before mentioning, near the end, that he could also paint. In Milan he designed a colossal bronze horse that was never cast, staged court festivals and painted The Last Supper (c. 1495–1498) on a refectory wall, in an experimental technique that began flaking within his lifetime. Later he served Cesare Borgia as a military engineer, returned to Florence, began the Mona Lisa around 1503, and from 1513 spent three years in Rome, overshadowed by younger stars such as Michelangelo and Raphael. He died in 1519 at Amboise as the guest of the French king, Francis I.

The real work was in the notebooks. More than 7,000 pages survive, much of them written right to left in mirror script and crowded with drawings: water swirling round obstacles, the branching of trees, the flight of birds, gears, pumps, fortifications and flying machines. He dissected human corpses, by his own account more than thirty, and drew the heart, the skull and a foetus in the womb with a precision that anatomical illustration would take generations to match. His guiding idea was saper vedere, knowing how to see.

Did you know? The Codex Leicester, Leonardo's notebook on water, rocks and fossils, was bought by Bill Gates in 1994 for about $30.8 million.

It is easy to inflate him. Most of his machines were never built, many would not have worked, and his discoveries stayed in private papers rather than shaping science directly; much of the anatomy was not published for centuries. A parachute built to his design was tested successfully only in 2000. Fewer than twenty surviving paintings are generally accepted as his, and he abandoned commissions often enough to exasperate his patrons.

Yet he stands for something real. Renaissance workshops treated art as a form of knowledge, and Leonardo pushed that idea further than anyone: to paint a smile, study the muscles of the face; to draw a river, understand turbulence. His life also shows the limits of the age, because knowledge locked in a notebook changes little. The printing press, already spreading through Italy, was solving that problem. Curiosity was his method, and the whole visible world was his syllabus.

The Reformation Splits

On 31 October 1517 Martin Luther, a friar and professor at the small university of Wittenberg in Saxony, sent out his Ninety-five Theses attacking the sale of indulgences, papal pardons said to shorten time in purgatory. In Germany the Dominican Johann Tetzel was preaching them to raise money, partly to rebuild St Peter's Basilica in Rome. Whether he really nailed them to a church door is uncertain; the story first appears after his death. What is certain is that printers had them in circulation within weeks, and in German soon after.

The protest grew into a theology. Salvation, Luther argued, came by God's grace through faith alone, and scripture alone was the final authority, above popes and councils. Excommunicated in 1521, he refused to recant before Emperor Charles V at the Diet of Worms, then translated the New Testament into vigorous German while hidden in the Wartburg castle. Princes who protected him gained a theology that justified taking church lands and defying Rome.

The movement did not stay united. In Zurich, Huldrych Zwingli pushed reform further; in Geneva after 1541, John Calvin built a disciplined church whose Reformed model spread to the Netherlands, Scotland, Hungary and France. Radical Anabaptists rejected infant baptism and were persecuted by Catholics and Protestants alike. In England, Henry VIII broke with Rome in 1534 for reasons that had more to do with marriage and money than doctrine. Rome answered with a reform of its own: the Jesuit order, approved in 1540, and the Council of Trent (1545–1563) sharpened Catholic teaching and discipline.

Then came the wars. The German Peasants' War of 1524–1525, partly inspired by reforming preachers, was crushed with tens of thousands dead. The Peace of Augsburg in 1555 let each German prince choose Lutheranism or Catholicism for his lands. France endured decades of Wars of Religion, including the St Bartholomew's Day massacre of 1572. The Thirty Years' War (1618–1648) devastated central Europe, with estimates of the dead ranging from about 4.5 to 8 million. The Peace of Westphalia in 1648 finally accepted that Western Christendom would remain divided.

Did you know? The word "Protestant" comes from the formal Protestation made by Lutheran princes and cities at the Diet of Speyer in 1529.

The Reformation reshaped far more than churches. It pushed the Bible into vernacular languages, encouraged ordinary believers to read, bound religious identity to the state and, through long and bitter experience, nudged some thinkers towards toleration. Its leaders were no friends of pluralism; Calvin's Geneva burned the dissenter Michael Servetus in 1553. Spain, Italy, Poland and Ireland remained firmly Catholic, and Eastern Orthodoxy, far from Wittenberg, was largely untouched. The single church of the Latin West was gone for good.

The Ming Voyages

In 1405 a fleet left the mouth of the Yangtze larger than anything Europe would send to sea for a century. By the Ming dynasty's own records it numbered more than 300 ships and some 27,000 men. Its commander was Zheng He, a Muslim from Yunnan who had been captured as a boy, castrated and raised to power in the household of the prince who became the Yongle Emperor.

Between 1405 and 1433 Zheng He led seven voyages. The fleets sailed by way of Champa and Java to Malacca, which became a fortified depot, then across the Bay of Bengal to Sri Lanka and to Calicut on the pepper coast of India. Later expeditions reached Hormuz at the mouth of the Persian Gulf, Aden, and the Swahili coast of East Africa at Mogadishu and Malindi, while smaller detachments took envoys towards Mecca. Ships returned with ambassadors, pepper, gems and exotic animals, including a giraffe presented at court in 1414 and hailed as a qilin, an auspicious beast. The Muslim interpreter Ma Huan, who sailed on three of the voyages, left a vivid account of the ports they visited.

The purpose was not conquest, nor trade for profit in the later European sense. The voyages displayed Ming power, drew distant rulers into the tributary system and burnished the legitimacy of an emperor who had seized the throne from his nephew. They were not purely peaceful: Zheng He fought pirates near Palembang and brought a captured Sri Lankan king back to China. The largest "treasure ships" are recorded as more than 120 metres long, but many historians doubt that wooden ships of that size were practical, and the true dimensions remain disputed.

Then the fleets stopped. Yongle died in 1424 and his successor halted the voyages. A seventh expedition sailed under the Xuande Emperor in 1431–1433, and Zheng He probably died during or soon after it. The fleets were ruinously expensive, Confucian officials distrusted the eunuchs who ran them, and the empire's most pressing danger lay on the northern steppe, where Oirat Mongols captured an emperor in 1449. Restrictions on private seafaring, the haijin, had been in force since the dynasty's founder, and the great shipyards decayed.

Did you know? The claim that Zheng He's ships reached the Americas in 1421 is rejected by historians; there is no reliable evidence for it.

China did not vanish from the sea. Chinese merchants, often in defiance of the bans, kept trading across Southeast Asia, and Ming demand for silver would soon draw in the treasure of the Americas. But the state withdrew. When Vasco da Gama reached Calicut in 1498 with three ships, no imperial fleet stood in his way. At sea, power belongs to those who keep coming back.

Banking Powers Art

In 1397 Giovanni di Bicci de' Medici set up a bank in Florence. Within a generation it was the most important financial house in Europe, with branches in Rome, Venice, Milan, Geneva, Bruges, London and Avignon, and the coveted role of banker to the papacy, handling church revenues gathered from across Latin Christendom. The family emblem of red balls, the palle, became a familiar sight on the buildings it paid for.

The bank's genius lay in organisation and paperwork. Each branch was a separate partnership with a local manager who held a share of the profits, so one branch's failure need not sink the rest. The key instrument was the bill of exchange: a merchant paid florins in Florence and his agent collected an equivalent sum in another currency in Bruges or London some months later. The margin built into the exchange rates was, in effect, interest, which neatly sidestepped the Church's ban on usury. Italian firms kept their books by double-entry bookkeeping, a method the friar Luca Pacioli described in print in 1494.

Money became power. Giovanni's son Cosimo (1389–1464) returned from exile in 1434 and dominated Florence for thirty years without holding a formal throne, steering elections through friends, allies and debtors. He poured money into building: Brunelleschi's church of San Lorenzo, the family palace by Michelozzo, the friary of San Marco frescoed by Fra Angelico, and a library there open to scholars. Patronage was piety, publicity and, many suspected, a kind of penance for a fortune made from interest.

His grandson Lorenzo the Magnificent (1449–1492) was a poet and diplomat more than a banker. His circle included Botticelli, the philosopher Pico della Mirandola and the teenage Michelangelo, who lived in his household. But the bank was declining under weak managers and bad loans, including large sums lent to the English king Edward IV during the Wars of the Roses and to the dukes of Burgundy. In 1494 the Medici were driven out of Florence and the bank collapsed. The fiery friar Girolamo Savonarola then dominated the city, presiding over bonfires of vanities in which paintings, books and mirrors were burned.

Did you know? The Medici later produced three popes, Leo X, Clement VII and Leo XI, and two queens of France, Catherine and Marie de' Medici.

The family returned in 1512 and later ruled Tuscany as grand dukes. One of its popes, Leo X, presided over the indulgence campaign for St Peter's Basilica that provoked Martin Luther. Others copied the model: the Fugger of Augsburg financed Habsburg emperors from silver and copper mines. Not all Renaissance art was paid for by bankers; guilds, churches, city councils and princes commissioned much of it. But the Medici show how the system worked. Profits earned in Bruges and London ended up as frescoes in Florence.

A New Sky

For some 1,400 years, educated people from Baghdad to Oxford pictured the cosmos much as the Alexandrian astronomer Ptolemy had described it around 150 CE. The Earth sat motionless at the centre, and the Moon, Sun, planets and stars wheeled around it, with small extra circles called epicycles to explain why planets sometimes seem to move backwards. The system was intricate, but it predicted the sky well enough for calendars and astrology, and it matched both common sense and Aristotle's physics. Islamic astronomers refined it for centuries at observatories such as Maragha and Samarkand.

Nicolaus Copernicus (1473–1543), a church canon working in Frombork on the Baltic coast of Poland, proposed another arrangement. In On the Revolutions of the Heavenly Spheres, printed in Nuremberg in 1543, the year he died, he put the Sun near the centre and made the Earth a planet, spinning daily on its axis and circling the Sun once a year. The backward loops of Mars and Jupiter became an illusion, the effect of a faster Earth overtaking slower planets. The idea was not entirely new. Aristarchus of Samos had proposed a Sun-centred cosmos around 270 BCE, and astronomers at Maragha in Persia and Ibn al-Shatir in Damascus had devised geometrical models that reappear, strikingly, in Copernicus's work.

Copernicus had held back his book for decades; his young disciple Georg Joachim Rheticus finally persuaded him to let it be printed. At first the new system was neither simpler nor more accurate. Copernicus kept perfect circles and still needed epicycles. An unsigned preface added by the Lutheran theologian Andreas Osiander presented the book as a mere device for calculation, and for decades most astronomers used its tables while setting aside its cosmology.

The evidence came later. In Denmark, Tycho Brahe compiled the most precise naked-eye observations ever made. From them, Johannes Kepler showed in 1609 that planets move in ellipses, not circles. In 1610 Galileo reported that his telescope revealed moons circling Jupiter, and he soon observed the phases of Venus, which fitted a Sun-centred scheme far better than Ptolemy's. In 1616 the Church suspended Copernicus's book "until corrected"; in 1633 Galileo was tried and confined to house arrest for defending it. Isaac Newton's Principia of 1687 finally explained why the planets move as they do.

Did you know? The popular idea that medieval Europeans thought the Earth was flat is a myth; educated people had known it was a sphere since antiquity.

Copernicus moved humanity off the physical centre of the universe. Later thinkers would count it as the first of several such demotions. Within a few generations a Sun-centred cosmos was common knowledge among educated Europeans, and astronomy answered to measurement rather than authority. The sky had not changed; humanity's place in it had.

Humanism's Wager

The word humanist began as a job description. In 15th-century Italy an umanista was a teacher of the studia humanitatis: grammar, rhetoric, poetry, history and moral philosophy, studied through classical Latin and, increasingly, Greek. The programme sounds modest. Its wager was not: that studying the best human writing would produce wiser, freer and more capable people, fit to govern themselves and their cities.

The movement's pioneers were often civil servants. Coluccio Salutati and Leonardo Bruni, chancellors of Florence, used Cicero's ideal of the active citizen to defend their republic against the dukes of Milan. Teachers such as Vittorino da Feltre, whose school at Mantua mixed Latin with exercise and games, built a curriculum that would shape European grammar schools for centuries. The humanists' cry was ad fontes, back to the sources: read the original text, not the commentary on the commentary.

That habit could be explosive. Around 1440 Lorenzo Valla showed that the Donation of Constantine, a document in which the emperor supposedly handed authority over the western empire to the pope, was a forgery: its Latin belonged to centuries after Constantine. In 1486 the young Giovanni Pico della Mirandola wrote a speech later titled the Oration on the Dignity of Man, in which God tells Adam that he alone has no fixed place in creation and may shape himself into whatever he chooses.

Did you know? Pico planned a public debate in Rome on 900 theses in 1487; Pope Innocent VIII suspended it, and a papal commission condemned 13 of them.

Humanism was not anti-religious. North of the Alps, Erasmus of Rotterdam published a Greek New Testament with a fresh Latin translation in 1516, aiming to renew Christianity through better texts; Luther used it for his German Bible. Thomas More's Utopia, from the same year, imagined a rational commonwealth in order to criticise his own. These Christian humanists wanted faith, reason and human dignity to work together, though the Reformation would soon test that harmony to breaking point. Erasmus's Praise of Folly (1511) mocked corrupt clergy so sharply that contemporaries said Erasmus laid the egg that Luther hatched.

The wager had limits. Humanist schooling served a small and mostly male elite; a few women, such as the Venetian scholar Cassandra Fedele, won fame precisely because they were exceptions. The same age that praised human dignity also saw the conquest of the Americas and the growth of the Atlantic slave trade. Nor was respect for human worth invented in Florence; Confucian, Islamic and other traditions had long arguments of their own about it. But humanism fixed in Europe's schools the idea that people should be educated to think, speak and judge for themselves. The classroom became a quiet engine of change.

Ideas Become Cheap

A handwritten heresy could be contained: find the copies, burn them, and if necessary burn the author. That was how the Church dealt with Jan Hus of Prague, burned at the Council of Constance in 1415, and with the books of the English reformer John Wycliffe. Print changed the arithmetic. When copies number in the thousands and printers work in dozens of cities, suppression becomes a game of catch-up that authorities rarely win.

The first great test was Luther. From 1517, cheap German pamphlets, or Flugschriften, poured from the presses: a few sheets folded into a small booklet, sold for a few pennies. Luther was the star author. By one widely cited estimate, his writings made up around a third of all German-language publications sold between 1518 and 1525. The workshop of Lucas Cranach added woodcuts that made the message plain even to people who could not read, and only a minority could. Cranach's Passional Christi und Antichristi of 1521 set scenes of Christ's humility beside the pope's pomp, page by page. Pamphlets were read aloud in homes, taverns and marketplaces, so one copy might reach dozens of listeners.

Authorities fought back with the same machinery. The Church issued lists of banned books, culminating in the papal Index of Prohibited Books of 1559. Kings licensed printers; in England the Stationers' Company received a royal charter in 1557 that helped the crown police the trade. William Tyndale's English New Testament, printed at Worms in 1526, was smuggled into England, burned by bishops and reprinted abroad; Tyndale himself was strangled and burned near Brussels in 1536. Within a few years, Henry VIII had authorised an English Bible for every parish church.

Censorship could slow ideas but not stop them. Europe was politically fragmented, and a book banned in Paris could be printed in Geneva, Basel or Antwerp and carried back across a border. Catholics used print too, for catechisms and polemic, and both sides learned that a cheap pamphlet could raise an army of opinion. Elsewhere the press spread on different terms: in the Ottoman Empire, Jewish printers were at work in Istanbul by around 1500, but a press for Ottoman Turkish books was not established until the 1720s, for reasons historians still debate.

Did you know? The Catholic Church's Index of Prohibited Books was revised for four centuries and formally abolished only in 1966.

The deeper change was in the economics of dissent. Once copying is cheap, the bottleneck shifts from making copies to winning readers, and ideas must compete in a market. That market would later carry scientific journals, newspapers and revolutionary tracts. Rulers kept trying, with licences, stamps and prosecutions, for centuries. Cheap ideas are hard to govern.

The West Wakes Up

Around 1450, Europe did not look like a future master of the world. The Ottoman sultan Mehmed II took Constantinople in 1453 with the help of giant cannon cast by a Hungarian founder. Ming China was larger, more populous and at least as productive, and its fleets had recently sailed to Africa. The Mamluk sultans of Egypt controlled the spice route through the Red Sea, and in the Americas the Inca and Aztec states were expanding fast. Western Europe sat on the Atlantic edge of Eurasia, split into rival kingdoms and city-states. In West Africa, Songhay was building an empire along the Niger, and the kingdom of Kongo was a powerful state in central Africa.

Yet within seventy years Europeans were sailing round Africa and across the Atlantic. Portuguese captains, encouraged since the days of Prince Henry, worked their way down the African coast; Bartolomeu Dias rounded the Cape of Good Hope in 1488, and Vasco da Gama reached Calicut in 1498. In 1492 Christopher Columbus, sailing for Castile, reached the Caribbean. In 1519 Ferdinand Magellan's fleet set out on what became the first voyage round the world, and Hernán Cortés landed in Mexico to begin the conquest of the Aztec empire.

Why Europe, and why then? Historians have argued for generations. Part of the answer lies in the forces traced in the preceding chapters. Print spread maps, travel accounts and technical manuals cheaply. Humanism prized inquiry and argument. Italian-style banking could finance risky ventures. And competition between states meant that a project rejected in one capital could be sold in another: Columbus was turned down by Portugal before Ferdinand and Isabella backed him. Political fragmentation, a weakness in war, worked as an insurance policy for ideas.

Geography and greed mattered as much as curiosity. Atlantic wind systems, ocean-going caravels and gunpowder weapons made the voyages possible; a hunger for spices, gold and converts made them attractive. The Ottoman and Mamluk grip on eastern trade gave Europeans a powerful reason to look for another way round. Ming China, with its vast internal market, had far less need of distant voyages and had already chosen to stay home.

Did you know? Columbus never accepted that he had found a new continent; to the end of his life he maintained that his landfalls lay near Asia.

The awakening was not benign. It would bring conquest, epidemics that killed a large share of the peoples of the Americas, and the Atlantic slave trade. Nor did Europe suddenly become richer than everyone else: the decisive gap in wealth, the Great Divergence, opened only centuries later. What had changed was momentum. The rim of the Old World was about to become its storm centre.

1492 Changes Everything

In the small hours of 12 October 1492, a lookout on the Pinta sighted a pale shoreline under the moon. By morning Christopher Columbus, a Genoese navigator sailing for the Crown of Castile, had waded ashore on a small island in the Bahamas that its Taíno inhabitants called Guanahani. He renamed it San Salvador and was sure he stood on the outer fringe of Asia. He was wrong by an ocean and a continent.

The voyage grew out of a race. Portugal was working its way round Africa towards the spice markets of India, and Bartolomeu Dias had rounded the Cape of Good Hope in 1488. Columbus offered a shortcut west. The popular story that his critics feared he would sail off the edge of a flat Earth is a myth: educated Europeans had known the world was round since antiquity. The real quarrel was about size. Columbus shrank the globe, placing Japan roughly 2,400 nautical miles west of the Canary Islands, when the true distance is more than four times that. The royal experts who doubted him were right. Only the fall of Granada in January 1492 freed Ferdinand and Isabella to take the gamble.

Three ships, the Niña, the Pinta and the Santa María, left the port of Palos on 3 August with about 90 men. After refitting in the Canaries they caught the north-east trade winds on 6 September and crossed in about five weeks. The Santa María ran aground off Hispaniola on Christmas Day, and 39 men were left behind in a makeshift fort, La Navidad; none were alive when the second expedition arrived. Columbus made four voyages in all and died in 1506 apparently still insisting he had reached the Indies, which is why the Caribbean islands are called the West Indies to this day.

He was not the first outsider to arrive. Norse Greenlanders camped at L'Anse aux Meadows in Newfoundland around 1000 CE, and Polynesian voyagers probably touched South America, carrying the sweet potato back across the Pacific. But those contacts built no lasting bridge. Since the Bering land bridge drowned at the end of the last Ice Age, the peoples of the Americas had invented farming, cities, writing and empires on their own. After 1492 the link never closed again. Within two years the Treaty of Tordesillas (1494) had divided the newly found lands between Spain and Portugal along a line on a map, without consulting anyone who lived there.

Did you know? The name America first appeared on a world map printed by Martin Waldseemüller in 1507, honouring Amerigo Vespucci, who argued that these lands were a new continent rather than Asia.

What came next, the exchange of crops, animals and microbes in the chapters that follow, was nothing Columbus planned. His intentions were a footnote. His landfall rearranged the planet.

The Columbian Exchange

Before 1492 there were no tomatoes in Italy, no potatoes in Ireland, no chillies in India or Korea, and no horses, cattle or wheat anywhere in the Americas. Within a few generations all of that had changed. The historian Alfred W. Crosby gave the process its name in 1972: the Columbian Exchange, the two-way traffic of plants, animals, microbes and people that followed Columbus across the Atlantic.

The traffic began at once. Columbus's second voyage in 1493 carried horses, cattle, pigs, sugar cane and wheat to Hispaniola. Pigs, released to breed freely on islands and in forests, multiplied so fast that later Spanish expeditions could live off feral herds. Cattle spread across the grasslands of Mexico and the Argentine pampas. Horses escaped or were traded north, and after the Pueblo Revolt of 1680 they spread rapidly onto the Great Plains. By the eighteenth century the Comanche and Lakota had built new mounted ways of life around an animal their great-grandparents had never seen.

Going the other way were the crops of Indigenous American farmers, refined over thousands of years. Maize became a staple from southern Africa to northern China. Potatoes, domesticated in the Andes and grown in Spain by about 1570, yielded more calories per acre than any European grain and helped fuel population growth across northern Europe; one widely cited economic study credits the potato with roughly a quarter of the Old World's population increase between 1700 and 1900. Cassava fed much of Central Africa, sweet potatoes and maize carried Qing China's population upwards, and chillies conquered cuisines from Sichuan to Kerala. Cacao and tobacco created new European habits, and new fortunes.

Not everything travelled by choice. Sugar cane, carried west, became the crop that demanded the most brutal labour regime of the age, and the plantation complex of Brazil and the Caribbean drew millions of enslaved Africans across the ocean. With them came African rice-growing skills, crops such as okra and yams, and also malaria and yellow fever. The deadliest cargo of all was invisible: smallpox, measles, influenza and typhus, diseases against which the peoples of the Americas had no inherited resistance. The next chapter follows that catastrophe.

Did you know? Chilli peppers are native to the Americas, so before the sixteenth century the cooks of Thailand, India and Sichuan had never tasted one.

The exchange was lopsided. Europe and Asia gained new foods and land on which to grow them; the Americas gained livestock and wheat but lost most of their people. Biology, as much as gunpowder, decided who would inherit the New World.

Look at any dinner plate today and the Exchange is still sitting on it.

The Great Dying

Nobody counted the people of the Americas in 1492, and estimates of their number range wildly, from about 8 million to more than 100 million. Many scholars now favour something like 50 to 60 million. Whatever the starting figure, the shape of what followed is not in doubt. Within roughly a century the Indigenous population fell by something like 90 per cent, to perhaps 5 or 6 million. Historians call it the Great Dying, and it remains the largest proportional collapse of a population in recorded history.

The main killers were Old World infections: smallpox, measles, influenza, typhus and later malaria and yellow fever. Eurasian and African populations had lived with these diseases for centuries, many of them caught from domesticated animals that the Americas largely lacked. Survivors passed on a degree of resistance and children met the diseases young. In the Americas, every age group was exposed at once. When whole villages fell sick together, nobody was left to fetch water, tend fields or care for the dying, and hunger finished what fever began.

Smallpox reached Hispaniola around 1518 and Mexico in 1520, arriving with Spanish reinforcements while Hernán Cortés was fighting the Mexica. It tore through Tenochtitlan, killing the new emperor Cuitláhuac after only a few months on the throne, and the weakened city fell in August 1521. The disease then ran ahead of the Spanish along trade routes. The Inca ruler Huayna Capac probably died in an epidemic around 1527, before any Spaniard had reached Peru, and the civil war that followed between his sons Huáscar and Atahualpa left the empire divided when Francisco Pizarro arrived in 1532. Later waves of an illness the Nahua called cocoliztli, in 1545 and 1576, killed millions more in central Mexico.

Disease was not the whole story. Conquest, massacre, forced labour under the encomienda system, enslavement and the destruction of food supplies all multiplied the deaths, and the collapse was deepest where violence and epidemics came together. In North America the dying often preceded any lasting settlement. Hernando de Soto's expedition of 1539 to 1543 marched through populous chiefdoms in the south-east that later Europeans found largely empty, and an epidemic of 1616 to 1619 emptied much of the New England coast just before the Pilgrims landed at Plymouth.

Did you know? Some climate scientists argue that so much farmland reverted to forest after the Great Dying that the regrowth drew enough carbon from the air to help cool the planet around 1610.

The consequences shaped everything after. Europeans often found land already emptied, and told themselves it had always been wilderness. Spanish and Portuguese colonists, short of labour, turned increasingly to enslaved Africans. The conquest of the Americas is often told as a story of steel and horses. It was first a story of germs.

Silver Circles the Globe

In 1545 an Indigenous herder named Diego Huallpa is said to have found silver on a red, cone-shaped mountain high in the Andes, in what is now Bolivia. The mountain became the Cerro Rico, the "rich hill", and the mining town at its foot, Potosí, grew within decades to well over 100,000 people, one of the largest cities in the Americas. A year later silver was found at Zacatecas in Mexico. Together, Spanish America's mines would produce most of the world's silver for the next 250 years.

Getting the metal out depended on two things. The first was chemistry: the mercury amalgamation process, developed in Mexico in the 1550s and applied at Potosí in the 1570s with mercury from Huancavelica in Peru. The second was coercion. Viceroy Francisco de Toledo reorganised the old Inca labour draft into the mita, which forced Andean villages to send thousands of men a year into the mines, where many died of accidents and mercury poisoning.

The silver was cast into bars and minted into coins, above all the real de a ocho, the piece of eight. Much of it sailed in armed treasure fleets to Seville, where it paid Spain's soldiers and bankers and then drained out across Europe. Much of that, in turn, went east, because European traders had little else that Asian markets wanted. The Portuguese, then the Dutch and English East India Companies, paid for silks, spices and porcelain largely in silver.

The other route ran west. From 1565 the Manila galleons crossed the Pacific between Acapulco and the Philippines, once or twice a year, until 1815. Manila, founded as a Spanish city in 1571, became a meeting place where Chinese junks from Fujian exchanged silk and porcelain for American silver. The historians Dennis Flynn and Arturo Giráldez have argued that 1571 marks the birth of truly global trade, because from then on every inhabited continent was linked in a continuous exchange.

Why China? Ming China had the world's largest economy and, after experiments with paper money failed, a hunger for silver. The Single Whip reforms of the 1570s and 1580s, associated with the minister Zhang Juzheng, required many taxes to be paid in silver. Silver was worth more in China than in Europe, so merchants profited simply by carrying it there. Estimates vary, but a large share of all American silver, perhaps a third or more, ended up in China, along with much of Japan's silver output.

Did you know? The Spanish piece of eight was so widely used that it remained legal tender in the United States until 1857, and the US dollar itself was modelled on it.

Silver funded Spanish wars, fed inflation in Europe and kept China's tax system running. When supplies faltered in the seventeenth century, the shock was felt from Seville to Beijing. A single coin had made the world one market.

The Atlantic Slave Trade

Between 1501 and 1866, ships carried an estimated 12.5 million enslaved Africans across the Atlantic. About 10.7 million survived the voyage. These figures come from the Trans-Atlantic Slave Trade Database, built from the records of some 36,000 voyages, and they make this the largest forced migration in history. Behind every number was a person seized, sold, chained below deck and put to work for the profit of others.

Portuguese ships began buying captives on the West African coast in the 1440s, and the first direct voyages from Africa to the Americas followed in the 1520s. The trade grew with sugar. Plantations in Brazil, and later in Barbados, Jamaica and Saint-Domingue, consumed labour at a terrible rate, and planters found it cheaper to buy new captives than to keep the enslaved alive. The trade peaked in the eighteenth century, when roughly six million people were carried, many of them in British, Portuguese and French ships sailing from Liverpool, Bristol, Lisbon, Rio de Janeiro and Nantes.

The system is often called the triangular trade. European ships carried textiles, many of them Indian cottons, along with guns, iron bars and cowrie shells to the African coast. There African rulers and merchants, in states such as Dahomey and Asante, sold people mostly captured in wars and raids further inland. The largest numbers came from West Central Africa, the region of Kongo and Angola, followed by the Bights of Benin and Biafra, the Gold Coast and Senegambia. The crossing, the Middle Passage, usually took one to three months. Perhaps 1.8 million people died on board, from dysentery, smallpox, violence and despair. In 1781 the crew of the Zong threw more than 130 captives overboard and then claimed for them on insurance.

Most survivors did not go to North America. Brazil received the largest share, close to 5 million, and the Caribbean islands together took a similar number. Mainland North America received about 400,000, though its enslaved population later grew by natural increase. Their labour produced the sugar, tobacco, coffee and cotton that sweetened European tables and helped finance banks, ports and insurers.

Resistance was constant: shipboard revolts, runaway communities such as Palmares in Brazil, and finally the great revolution in Saint-Domingue that created Haiti in 1804. Britain abolished its trade in 1807 and the United States in 1808, but the Atlantic trade continued illegally for decades, and Brazil did not end slavery itself until 1888.

Did you know? More enslaved Africans landed in Brazil than in the whole of mainland North America, by a factor of more than ten.

The consequences outlived abolition by centuries. West and Central African societies lost millions of young adults. The Americas gained African languages, faiths, music and foods. And the racial ideas invented to justify slavery proved harder to abolish than the trade itself.

Gunpowder Empires

In the sixteenth century the three largest and wealthiest states west of China were not in Europe. They were the Ottoman Empire, from the Balkans to the Arab lands; the Safavid Empire of Iran; and the Mughal Empire of the Indian subcontinent. The historians Marshall Hodgson and William McNeill called them the gunpowder empires, because each used cannon and handguns, together with disciplined standing armies, to crush older rivals and hold enormous territories.

The Ottomans showed the way. In 1453 Mehmed II brought down the walls of Constantinople with giant bronze cannon, some cast by a Hungarian founder named Orban. Their elite Janissary infantry carried firearms early, and in 1514 at Chaldiran in north-west Iran, Selim I's artillery and musketeers shattered the cavalry of the young Safavid shah Ismail I. Selim went on to conquer Mamluk Syria and Egypt in 1516 and 1517.

The Safavids learned quickly. Ismail had founded the dynasty in Tabriz in 1501 and made Twelver Shi'ism the state religion, a choice that still shapes Iran. His descendant Abbas I (reigned 1588 to 1629) built a corps of musketeers and artillery from converted Georgian, Armenian and Circassian slave-soldiers, recovered lost provinces, and moved his capital to Isfahan, where he laid out one of the grandest public squares in the world.

In India, Babur, a Central Asian prince descended from both Timur and Chinggis Khan, defeated the far larger army of Ibrahim Lodi at the first battle of Panipat in 1526, using field guns and matchlocks behind a barricade of carts. His grandson Akbar (reigned 1556 to 1605) built the real empire: a ranked service nobility called the mansabdari system, a land survey that set taxes, and a policy of tolerance that abolished the tax on non-Muslims. With perhaps 100 million subjects or more, Mughal India was one of the most populous and productive states on Earth; Shah Jahan's Taj Mahal, built from about 1632, is its most famous monument.

The label has its critics. Guns alone did not make these states; revenue systems, trained administrators and alliances with local elites mattered at least as much, and Ming China and Muscovy used firearms too. But the three empires did share a world: Persian as a language of culture and government, trade along the same routes, and long, sometimes bitter rivalries with one another.

Did you know? Babur wrote a frank autobiography, the Baburnama, in his native Chagatai Turkic, describing battles, gardens, melons and his own drinking.

Their decline came in the eighteenth century. Afghan rebels took Isfahan in 1722, the Mughal state fragmented after Aurangzeb's death in 1707, and in 1739 the Persian ruler Nader Shah sacked Delhi and carried off the Peacock Throne. Europe's companies were watching.

The Ottoman Bridge

Around 1299 a Turkish chieftain called Osman led a small band of warriors on the frontier between the Seljuk sultanate and the Byzantine Empire in north-western Anatolia. His descendants, the House of Osman, would rule for more than six centuries, longer than almost any other dynasty in history. At their height they governed from Hungary to Yemen and from Algiers to Baghdad: the seam where Europe, Asia and Africa meet.

The early sultans expanded in both directions. They took Bursa in 1326, crossed into Europe in the 1350s and made Edirne a capital. A crushing defeat by Timur at Ankara in 1402 nearly ended the state, but it recovered, and in 1453 Mehmed II captured Constantinople and made it the imperial capital, known increasingly as Istanbul. Selim I added Syria, Egypt and the holy cities of Mecca and Medina in 1516 and 1517. Under Suleiman I (reigned 1520 to 1566), remembered in Turkish as Kanuni, the Lawgiver, Ottoman armies took Belgrade, won at Mohács in 1526 and besieged Vienna in 1529, while the admiral Hayreddin Barbarossa made the eastern Mediterranean an Ottoman lake.

Holding all this needed a distinctive system. At the top sat the sultan in Topkapı Palace, his government run by the Grand Vizier and the imperial council, the Divan. Through the devşirme, Christian boys from Balkan villages were taken, converted and trained as Janissary soldiers or palace officials, an elite owing everything to the sultan. Provincial cavalrymen held timar land grants in return for service. Sultanic law, kanun, worked alongside Islamic law administered by judges called kadis.

Religious communities, later called millets, ran many of their own affairs under their leaders: Orthodox Christians under the Patriarch of Constantinople, Armenians, and Jews. When Spain expelled its Jews in 1492, Bayezid II welcomed many of them, and Salonica became one of the great Jewish cities of the world. This was not equality, since non-Muslims paid extra tax and faced limits, but it was a working pluralism that kept a vast, mixed empire governable.

The bridge carried goods and ideas as well as armies. Coffee houses spread from Istanbul in the sixteenth century; Ottoman control of eastern Mediterranean trade was one reason Europeans sought sea routes round Africa.

Did you know? Tulips came to western Europe from Ottoman gardens in the sixteenth century, setting off the Dutch tulip craze of the 1630s.

Decline was slow, not sudden. The failed second siege of Vienna in 1683 and the Treaty of Karlowitz in 1699 began a long retreat in Europe. Yet the empire survived into the twentieth century, until defeat in the First World War brought the sultanate's abolition in 1922 and a Turkish republic in 1923. For six hundred years, the crossroads had one keeper.

Companies Rule Nations

On 31 December 1600 Elizabeth I granted a charter to a group of London merchants, giving them a monopoly of English trade east of the Cape of Good Hope. Two years later the Dutch went further. The Vereenigde Oostindische Compagnie, the VOC, founded in 1602, was a permanent company whose shares anyone could buy and trade on the new Amsterdam exchange. It is often called the first modern joint-stock company, and it was also something stranger: a business licensed to act like a state.

The VOC's charter allowed it to build forts, keep soldiers, make treaties with Asian rulers, wage war and coin money. It was run by a board of directors known as the Heeren XVII, the Seventeen Gentlemen. Under its governor-general Jan Pieterszoon Coen it seized Jayakarta on Java in 1619 and rebuilt it as Batavia, today's Jakarta. In 1621 Coen's forces conquered the Banda Islands, the world's only source of nutmeg, killing or enslaving most of the islanders and replacing them with plantations worked by enslaved labour. At its peak in the late seventeenth century the VOC employed tens of thousands of people and paid its shareholders handsome dividends.

The English East India Company began as the weaker rival, trading cotton textiles from bases at Surat, Madras, Bombay and Calcutta. It changed character in the 1750s as Mughal power fragmented. At Plassey in 1757 Robert Clive's small army, helped by the defection of the Nawab's commander Mir Jafar, defeated Siraj ud-Daulah, ruler of Bengal. In 1765 the Mughal emperor granted the Company the diwani, the right to collect the revenues of Bengal, Bihar and Orissa. A trading company had become the tax collector of one of the richest regions on Earth.

The results were often disastrous for those it governed. A famine in Bengal in 1770 killed millions while revenue collection continued. By the early 1800s the Company's private army numbered around 200,000 men, larger than the British Army itself. Parliament tried to rein it in with the Regulating Act of 1773 and the India Act of 1784, but the Company kept expanding until the Indian Rebellion of 1857. In 1858 the British Crown took over its territories, and the Company was finally dissolved in 1874. The VOC, bankrupt and corrupt, had been wound up in 1799.

Did you know? The English word loot comes from the Hindi lūṭ, and entered the language in the eighteenth century as the Company's armies spread across India.

These companies pioneered tools still in use: tradeable shares, limited liability, boards of directors and lobbying of governments. They also showed what happens when commercial power faces no counterweight. The questions they raised about who controls the largest corporations have never fully gone away.

The Little Ice Age

From roughly the fourteenth century to the middle of the nineteenth, much of the world was a little colder than before or since. The Little Ice Age was not a true ice age. Average temperatures in the Northern Hemisphere fell by well under one degree Celsius, and the cold came in irregular phases rather than as one long winter. But for societies living close to the margin of subsistence, a few cold, wet summers in a row could mean disaster. The worst phase came in the seventeenth century.

The causes were natural and overlapping. Clusters of large volcanic eruptions threw sulphur into the stratosphere and dimmed the sun; the eruption of Huaynaputina in Peru in 1600 was followed by one of the coldest summers in centuries across the Northern Hemisphere. Solar activity was unusually low: during the Maunder Minimum, from about 1645 to 1715, astronomers recorded remarkably few sunspots. Some researchers have also suggested that forests regrowing on land emptied by the Great Dying drew down carbon dioxide, a debated idea that would link this chapter to an earlier one.

The human consequences followed a grim chain: shorter growing seasons, failed harvests, soaring grain prices, hunger, disease and unrest. In Russia, the famine of 1601 to 1603 killed a large share of the population and helped plunge the country into the Time of Troubles. In northern China, drought and famine in the 1630s and 1640s fed the rebellions that ended the Ming dynasty: the rebel Li Zicheng took Beijing in 1644 and the last Ming emperor hanged himself, before the Manchu Qing seized the throne. The Ottoman Empire faced the Celali revolts, Mughal India suffered the Deccan famine of 1630 to 1632, and Europe endured the Thirty Years' War of 1618 to 1648, which may have killed a fifth or more of the German population.

The historian Geoffrey Parker called this a Global Crisis, counting revolts and wars on every inhabited continent during the mid-seventeenth century, including the English Civil War, the Fronde in France and revolts in Catalonia, Portugal and Naples. Climate did not cause these conflicts on its own. Taxes, religion and dynastic ambition all played their parts. But cold weather turned ordinary strains into breaking points.

Societies also adapted. Farmers turned to hardier crops, including American maize and potatoes; governments built granaries; Dutch engineers drained land and Dutch shipping thrived on the Baltic grain trade. In the Alps, glaciers advanced over farms and villages, and in Greenland the Norse settlements had already been abandoned by the fifteenth century.

Did you know? In the Great Frost of 1683 to 1684, the Thames in London froze so hard that a frost fair, with shops, printing presses and an ox roast, ran on the ice for weeks.

The lesson is uncomfortable and current. A small shift in average temperature can topple states that are already stretched. Climate has always been one of history's actors.

One World, Unequally

By the middle of the eighteenth century, a cup of sweetened tea in a London coffee house could tell the story of the whole world. The tea came from China, paid for partly in American silver. The sugar came from Jamaica, grown by enslaved Africans bought with Indian cotton cloth. The cup might be Chinese porcelain or a European copy of it. The planet had become, for the first time, a single connected economy.

The shares of that economy were not what we might expect. Asia was still the workshop of the world. By one well-known estimate, China and the Indian subcontinent together produced more than half of the world's manufactured goods around 1750. Qing China, under the Qianlong emperor, ruled perhaps 200 million people or more and absorbed silver from across the globe. Bengal's textiles clothed customers from West Africa to the Caribbean, so successfully that Britain passed the Calico Acts of 1700 and 1721 to protect its own weavers.

Yet the profits of connection were flowing in a particular direction. Britain, the Netherlands and France sat at the centre of networks they had built by force: chartered companies in Asia, sugar islands in the Caribbean, and the slave trade linking them all. Saint-Domingue, the French half of Hispaniola, became perhaps the most profitable colony in the world on the labour of hundreds of thousands of enslaved people. At the other end of the chains, the Andean villages of the mita, the plantation workers of Brazil and Jamaica, and the West African societies drained of young adults were deeply integrated into the global economy and saw little of its wealth.

Historians argue about how much this mattered for what came next. In 1944 the Trinidadian historian Eric Williams argued that the profits of slavery helped finance British industrialisation, a claim still debated. Kenneth Pomeranz's The Great Divergence (2000) argued that the most advanced parts of China and Europe were roughly comparable until about 1800, and that Britain's breakaway owed much to coal and to the "ghost acres" of its colonies, which supplied sugar, timber and cotton without using English land. The Seven Years' War of 1756 to 1763, fought in Europe, North America, India and West Africa, showed how global the competition between empires had become.

Did you know? Britain's Calico Act of 1721 banned the wearing of most printed cotton cloth, a law designed to shut out Indian textiles that British weavers could not yet match.

Not everyone was connected. Tokugawa Japan limited foreign trade to a few tightly controlled ports, and Aboriginal Australians would not face European colonisation until 1788. But the direction of travel was clear. The first global economy was built on exchange, conquest and slavery, and from the start it made some regions rich at the expense of others.

The industrial age that followed would widen that gap into a chasm. The world was one; it was not equal.

The Scientific Method

In 1610 Galileo Galilei turned a home-made telescope, magnifying about twenty times, on Jupiter and saw four small moons circling it. A planet with satellites of its own made nonsense of the old picture in which everything revolved around the Earth. What mattered as much as the discovery was the way it was made: look, measure, publish, and let anyone with a lens check. Over the next eighty years a loose network of European thinkers turned that habit into a system, the Scientific Revolution.

The ground had been prepared. In 1543 Nicolaus Copernicus published On the Revolutions of the Heavenly Spheres, placing the Sun at the centre, and in the same year Andreas Vesalius corrected centuries of anatomy by dissecting human bodies himself. Tycho Brahe's naked-eye observations, the most precise of their age, let Johannes Kepler show in 1609 that planets move in ellipses. Older traditions fed in too: the experimental optics of Ibn al-Haytham in eleventh-century Cairo, the numerals Europe borrowed from India via the Arab world, and the astronomy of Islamic observatories from Maragha to Samarkand.

The new scientific method was a loop rather than a rulebook. Francis Bacon urged gathering observations and testing general claims against them; René Descartes championed doubt and mathematics. In practice, natural philosophers observed, proposed an explanation, designed an experiment that could prove it wrong, and revised. Crucially, they did it in public. The Royal Society, founded in London in 1660, took the motto Nullius in verba, “take nobody's word for it”, and from 1665 its Philosophical Transactions printed results for rivals to check.

The method had costs for its pioneers. In 1633 the Roman Inquisition forced Galileo to recant his support for Copernicus and kept him under house arrest until his death in 1642. The defiant mutter “And yet it moves” is almost certainly a later legend. But the ideas crossed borders faster than censors could follow, printed in Leiden and Amsterdam, where the presses were freer.

The climax came in 1687, when Isaac Newton's Principia showed that a single law of gravitation governed a falling apple and the orbiting Moon. Heaven and Earth obeyed the same mathematics. Newton's picture would itself be revised by Einstein two centuries later, which is precisely the point: science is less a set of facts than a reliable way of correcting them.

Did you know? Newton wrote more about alchemy and theology than about physics; John Maynard Keynes, who bought many of his papers in 1936, called him “the last of the magicians”.

The same confidence soon turned from the heavens to human society, and the Enlightenment began to ask whether kings and churches could survive the test. Doubt, organised, became humanity's most productive habit.

The Enlightenment

If the Scientific Revolution showed that nature obeyed knowable laws, the Enlightenment asked the obvious next question: why not society too? From the 1680s to the end of the eighteenth century, writers across Europe and its colonies set out to examine government, religion, punishment and trade by the light of reason rather than custom. Immanuel Kant summed up the mood in 1784 with a motto borrowed from the Roman poet Horace: Sapere aude, “Dare to know”.

The foundations were laid in England. John Locke's Two Treatises of Government (1689) argued that people have natural rights to life, liberty and property, and that a government which violates them may be resisted. In France, Montesquieu's The Spirit of the Laws (1748) proposed separating legislative, executive and judicial power so that none could become tyrannical. Voltaire mocked religious intolerance, and Rousseau opened The Social Contract (1762) with “Man is born free, and everywhere he is in chains.” In Milan, Cesare Beccaria's On Crimes and Punishments (1764) attacked torture and the death penalty, and in 1776 the Scot Adam Smith's The Wealth of Nations made the case for open markets.

Ideas moved through a new infrastructure: cheap print, coffee houses, learned academies, Masonic lodges and the Paris salons hosted by women such as Madame Geoffrin. The movement's monument was the Encyclopédie of Denis Diderot and Jean d'Alembert, published between 1751 and 1772 in 28 volumes with more than 70,000 articles, an attempt to put all useful knowledge into readers' hands. Some rulers, the so-called enlightened despots Frederick the Great of Prussia and Catherine the Great of Russia, borrowed the vocabulary while keeping their thrones firmly in place.

The movement had blind spots that its own logic would later expose. Locke held shares in the Royal African Company, which traded enslaved Africans, and many philosophes wrote of universal rights while excluding women, the poor and non-Europeans. Yet a principle, once printed, is a lever anyone can pick up. Mary Wollstonecraft's A Vindication of the Rights of Woman (1792) applied it to women, and abolitionists on both sides of the Atlantic applied it to slavery.

Did you know? In 1784 a Berlin journal printed rival answers to the question “What is Enlightenment?”, one from Kant and another from the Jewish philosopher Moses Mendelssohn.

The Enlightenment's claims were radical because they were portable. Within a few decades they would reappear, sometimes almost word for word, in Philadelphia, Paris and Port-au-Prince. “All men are created equal” began life as a philosopher's premise. It ended as a political demand.

The Steam Engine

For all of history before about 1700, nearly every unit of work came from muscle, human or animal, plus whatever wind and falling water could be caught. That was a hard ceiling. Economies could grow, but population tended to rise and swallow the gains, the trap later named after the economist Thomas Malthus. The steam engine broke the ceiling by turning the ancient sunlight stored in coal into motion.

The first practical engine was built to solve a coal problem. British mines flooded as they went deeper, and in 1712 Thomas Newcomen, an ironmonger from Dartmouth, set up an atmospheric engine near Dudley Castle to pump them out. Steam filled a cylinder, a jet of cold water condensed it, and the pressure of the air pushed the piston down. It was hugely wasteful, but at a pithead the fuel was almost free.

James Watt, an instrument maker at the University of Glasgow, saw the waste while repairing a model Newcomen engine in 1763–64. His answer, patented in 1769, was a separate condenser, so the cylinder could stay hot. Watt's engines did the same work on roughly a quarter of the coal. In partnership with the Birmingham manufacturer Matthew Boulton he added rotary motion in the 1780s, which let engines turn machinery rather than merely pump water. Within a few decades Boulton and Watt engines were draining Cornish tin mines, blowing air into iron furnaces and driving cotton mills. His name survives as the unit of power.

Steam then went mobile. Richard Trevithick ran a high-pressure locomotive at Penydarren in Wales in 1804. George and Robert Stephenson's Rocket won the Rainhill Trials in 1829, and in 1830 the Liverpool and Manchester Railway opened as the first intercity line worked entirely by steam. Steamships were crossing the Atlantic by 1838. Britain's coal output, a few million tonnes a year around 1700, reached roughly 50 million tonnes by 1850 and well over 200 million by 1900, though estimates vary.

Did you know? Hero of Alexandria described a spinning steam-driven sphere, the aeolipile, in the first century CE, but it remained a curiosity rather than a machine.

Why Britain, and why then? Historians point to coal lying near the surface and near the coast, wages high enough to make labour-saving machines pay, a culture of practical tinkerers backed by patents, and booming markets for cloth and iron. Other regions had some of these advantages; Britain had them together. The engine also began the long story of fossil carbon in the atmosphere, a bill that would be presented two centuries later. In the meantime the effect was simple and staggering: power that never got tired.

The Great Divergence

In 1700 the most productive regions on Earth probably included the Yangtze delta in China, Bengal and Gujarat in India, and the North Sea coasts of Britain and the Low Countries, with surprisingly little to choose between their best-off districts. Qing China and Mughal India together produced nearly half of the world's output, largely because they held around half of its people. Then, within roughly a century, north-western Europe pulled decisively ahead. Historians call this the Great Divergence, a phrase popularised by Kenneth Pomeranz's book of that name in 2000.

The numbers are estimates, mostly reconstructed by the economist Angus Maddison and his successors, and should be read as orders of magnitude. On those figures China's share of world output was around a third in 1820, larger than all of western Europe's. By 1913 it had fallen below a tenth, India's had dropped from about a sixth to under a tenth, and western Europe and the United States together produced roughly half. Income per head in Britain, broadly comparable with the richest parts of Asia around 1700, was several times higher by 1900.

Why? The old explanations, European genius or Asian stagnation, have not survived scrutiny. Song China had smelted iron and printed books on an industrial scale centuries before Europe, and Indian cotton cloth dominated world markets well into the 1700s. Pomeranz stressed two strokes of luck: coal seams close to Britain's industrial centres, and colonies in the Americas that supplied land-hungry goods such as cotton, sugar and timber, much of it grown by enslaved Africans. Other historians emphasise high British wages that made machines worth building, rival European states that funded science and war, or institutions that protected investors.

Once the gap opened, power widened it. Machine-made British cloth undercut the handloom weavers of Bengal, which the East India Company had ruled since its victory at Plassey in 1757. In the Opium Wars of 1839–42 and 1856–60, British steam-powered gunboats forced China to open its ports and cede Hong Kong. Industrial muscle turned into imperial reach, and imperial reach into further wealth.

Did you know? By the economic historian Paul Bairoch's estimates, China and the Indian subcontinent together made more than half of the world's manufactured goods as late as 1750.

The divergence was not destiny. Japan began industrialising after 1868, and from the late twentieth century China, India and other Asian economies began closing the gap at a speed that mirrored how fast it had opened. Seen across two thousand years, Western dominance looks less like the rule than a long and consequential interlude.

The American Experiment

On 4 July 1776 delegates of thirteen British colonies, meeting in Philadelphia, adopted a Declaration of Independence drafted largely by Thomas Jefferson. Its second sentence turned Enlightenment philosophy into a founding charter: that “all men are created equal”, that they are endowed with rights including “Life, Liberty and the pursuit of Happiness”, and that governments derive “their just powers from the consent of the governed”. A quarrel over taxes and representation had become a claim about the purpose of government itself.

Winning that claim took eight years of war. George Washington's Continental Army survived near-collapse, and the decisive turn came with French money, troops and ships: at Yorktown in 1781 a Franco-American force trapped a British army. The Treaty of Paris recognised independence in 1783. France's generosity helped to bankrupt its own crown, with consequences that the next chapter will make plain.

The first national government, under the Articles of Confederation, proved too weak to raise taxes or pay its debts. In the summer of 1787, 55 delegates met behind closed doors in Philadelphia and wrote the Constitution: a federal republic in which Congress, a president and the courts check one another, much as Montesquieu had recommended. James Madison was its chief architect. Ratification was fiercely contested, partly through the Federalist essays, and was secured on a promise of amendments. The first ten, the Bill of Rights, took effect in 1791, protecting freedom of speech, religion and the press and the right to a fair trial.

The idea was flawed at birth, and many of the founders knew it. Nearly 700,000 people were enslaved in the new republic at the first census in 1790, and the Constitution counted each enslaved person as three-fifths of a person when sharing out seats in Congress. Women could not vote, except for a few decades in New Jersey; most states required voters to own property; Native American nations were treated as obstacles to expansion. Jefferson himself enslaved more than 600 people over his lifetime.

Did you know? The US Constitution is the oldest written national constitution still in force, and in more than two centuries it has been amended only 27 times.

Yet the words proved bigger than their authors. Abolitionists such as Frederick Douglass, and later Martin Luther King Jr, quoted the Declaration back at the nation, and amendments after the Civil War abolished slavery and promised equal protection of the laws. Revolutionaries from Paris to Caracas studied the American documents closely. The experiment's real innovation was a promise that could be held against the very people who made it.

The French Revolution

By 1788 the French crown was broke. Wars, including its costly support for the American rebels, had piled up debt, and a tax system riddled with exemptions for nobles and clergy could not pay it off. A ruined harvest pushed the price of bread to record highs. In January 1789 the Abbé Sieyès asked in a famous pamphlet what the Third Estate, the commoners, really was: “Everything.” And what had it been until now? “Nothing.” King Louis XVI had already summoned the Estates-General, an assembly that had not met since 1614, for May 1789.

The Third Estate, representing roughly 98 per cent of the population, declared itself a National Assembly in June and swore the Tennis Court Oath not to disband until France had a constitution. On 14 July Parisian crowds stormed the Bastille, a royal fortress holding just seven prisoners but a potent symbol of arbitrary power. In August the Assembly abolished feudal privileges and issued the Declaration of the Rights of Man and of the Citizen: “Men are born and remain free and equal in rights.” Radicals sat to the left of the chamber and conservatives to the right, giving politics a compass it still uses.

Monarchy and revolution could not share the country for long. The royal family's failed flight to Varennes in 1791 destroyed trust; war with Austria and Prussia from 1792 raised the stakes; in September 1792 France became a republic, and in January 1793 Louis was guillotined. Facing invasion, civil war in the Vendée and hunger, the Committee of Public Safety, with Maximilien Robespierre as its best-known voice, launched the Terror. Around 17,000 people were officially sentenced to death, and tens of thousands more died in prison or in summary killings. The war in the Vendée cost far more lives still, well over 100,000 by most estimates.

Then the Revolution devoured its makers. Georges Danton went to the guillotine in April 1794, Robespierre himself in July, overthrown in the coup of Thermidor. A weaker regime, the Directory, followed, until in November 1799 a young general, Napoleon Bonaparte, seized power. In 1804 he crowned himself emperor, an ending that seemed to mock the beginning.

Did you know? The revolutionaries even remade time: their calendar counted years from the Republic's founding in 1792, used ten-day weeks and named months after the weather, such as Thermidor, the month of heat.

Yet much survived the wreckage: the metric system, the end of feudal dues, the idea of the nation as a body of equal citizens, and Napoleon's Civil Code, exported across Europe by his armies. The slogan liberté, égalité, fraternité outlasted every regime that used it. So did the Revolution's warning.

The Haitian Revolution

In the 1780s the French colony of Saint-Domingue, the western third of the island of Hispaniola, was the most profitable colony in the world. By common estimates it supplied around 40 per cent of the sugar and some 60 per cent of the coffee consumed in Europe. That wealth rested on roughly half a million enslaved Africans, who outnumbered the 30,000 or so white colonists by more than ten to one and died so quickly that the plantations depended on a constant stream of new captives. Between them stood about 28,000 free people of colour, some of them planters and slaveholders themselves.

The French Revolution's talk of rights reached the island and split its free population. In August 1791, after a gathering at Bois Caïman led, according to tradition, by the Vodou priest Dutty Boukman, the enslaved of the Northern Plain rose; within weeks hundreds of plantations were burning. Out of the chaos emerged Toussaint Louverture, a formerly enslaved coachman who had won his freedom in the 1770s, and who proved a brilliant general and an even shrewder diplomat.

The colony became a battlefield for France, Spain and Britain. French commissioners declared emancipation in 1793 to win the rebels' support, and in 1794 Paris abolished slavery throughout its colonies. Toussaint, now fighting for France, drove out the British and Spanish, and by 1801 he governed the whole island under a constitution that made him governor for life.

Napoleon wanted the old, profitable colony back. In 1802 he sent his brother-in-law Charles Leclerc with a large expedition. Toussaint was lured into negotiations, arrested and shipped to France, where he died in a cold fortress in the Jura mountains in 1803. When it became clear that the French meant to restore slavery, as they had just done in Guadeloupe, resistance flared again under Jean-Jacques Dessalines. Yellow fever and fierce fighting destroyed the French army, which lost tens of thousands of men, Leclerc among them. After defeat at Vertières in November 1803 the French withdrew, and on 1 January 1804, at Gonaïves, Dessalines declared the independence of Haiti, reviving a name used by the island's Taíno people.

Did you know? The loss of Saint-Domingue helped persuade Napoleon to sell the vast Louisiana territory to the United States in 1803, roughly doubling the young republic's size.

The new state paid dearly for its freedom. Slaveholding powers shunned it; the United States withheld recognition until 1862; and in 1825 France, backed by warships, demanded an indemnity of 150 million francs for lost “property”, a debt that weighed on Haiti for generations. The revolution terrified slaveholders from Virginia to Brazil and inspired the enslaved everywhere. It was the age's most radical revolution, and for too long its least taught.

Nations Are Invented

In 1794 the Abbé Grégoire reported to France's revolutionary Convention that, of some 28 million people, only about three million spoke French fluently; millions more spoke Breton, Occitan, Basque, Flemish, Alsatian German or local dialects. Most Europeans thought of themselves first as subjects of a dynasty, members of a faith, or people of a particular valley or town. The conviction that humanity falls naturally into nations, each with a shared language and past and each entitled to its own state, is largely an invention of the late eighteenth and nineteenth centuries. The scholar Benedict Anderson called nations “imagined communities”: no member will ever meet most of the others, yet all feel bound together.

The ingredients were new. Printing in everyday languages, then mass newspapers, created publics who read the same news on the same day. States built schools, conscript armies and railways that mixed regions and standardised speech. Scholars gathered, and sometimes invented, a national past: the Brothers Grimm published German folk tales from 1812, Elias Lönnrot compiled the Finnish epic Kalevala in 1835, and readers across Europe had already swooned over the “ancient” Scottish poems of Ossian, largely composed by James Macpherson in the 1760s.

The idea redrew maps. In Latin America, creole leaders such as Simón Bolívar and José de San Martín won independence for most of the Spanish mainland between 1810 and 1825, and Brazil broke from Portugal in 1822. Greece won independence from the Ottoman Empire in 1830, the same year Belgium rebelled against Dutch rule. Italy was unified in 1861 through Cavour's diplomacy and Garibaldi's volunteers, and Germany in 1871 through Bismarck's wars, its empire proclaimed in the Hall of Mirrors at Versailles. The Italian statesman Massimo d'Azeglio is credited with the line “We have made Italy; now we must make Italians.”

Beyond Europe, the idea served empires and their opponents alike. Meiji Japan after 1868 built a modern nation around the emperor, compulsory schooling and a standard Tokyo speech. In British India the Indian National Congress was founded in 1885, and Egyptian, Chinese and Ottoman reformers were soon speaking the same language of the nation.

Did you know? At Italian unification in 1861, by the most widely cited estimate, only about 2.5 per cent of the population spoke standard Italian; most used regional languages such as Neapolitan, Sicilian or Venetian.

Nationalism could liberate subject peoples, and it could turn neighbour against neighbour, as minorities who did not fit the new maps would discover in the twentieth century. After the First World War, Woodrow Wilson's talk of self-determination spread the principle worldwide. Today almost everyone on Earth holds a nationality. Few remember that someone had to invent it.

The Factory World

In 1771 Richard Arkwright opened a water-powered cotton-spinning mill at Cromford in Derbyshire and ran it in shifts around the clock. It was one of the first true factories: hundreds of workers under one roof, tending machines set to a pace nobody in the building controlled. Within a few decades steam engines freed such mills from riverbanks, they clustered in towns, and Lancashire became the spinning centre of the world.

Manchester, nicknamed Cottonopolis, grew from roughly 75,000 people in 1801 to more than 300,000 by 1851, depending on where its boundaries are drawn. The census of 1851 showed that Britain had become the first large country in which more people lived in towns than in the countryside. The new cities were built fast and badly: back-to-back housing, open sewers and cholera epidemics in 1832 and 1848. In 1845 Friedrich Engels, who worked at his family's Manchester firm, published The Condition of the Working Class in England, a furious portrait of its slums.

Work itself changed. On the farm, labour followed seasons and daylight; in the mill it followed the factory bell and the clock. Mill rules fined workers for lateness and idle talk, and overlookers kept the pace. Children were cheap and nimble, and made up a large share of textile workers in the early nineteenth century. Britain's Factory Act of 1833 banned the employment of children under nine in textile mills and appointed inspectors to enforce it, and the Ten Hours Act of 1847 limited the working day for women and young people.

The same process produced wealth on a scale never seen before. Cheap cloth, iron and later steel poured out of Britain, then Belgium, Germany, the United States and Japan. Real wages for British workers rose only slowly before about 1840 but climbed markedly later in the century. Workers organised to claim their share: the Chartists campaigned for votes for working men from 1838, trade unions grew, and in 1848 Karl Marx and Engels published The Communist Manifesto. The factory's reach was global from the start, running back to the slave-grown cotton of the American South and the ruined handloom weavers of Bengal.

Did you know? The Luddites who smashed textile machinery between 1811 and 1816 were mostly skilled workers protesting wage cuts and shoddy work, and Parliament made machine-breaking punishable by death in 1812.

The factory reorganised time, place and class all at once. The grandchildren of its first workers would vote, join unions and buy the goods their families made. The long argument over who should share the wealth of machines began on the mill floor.