THE PRINTABLE STUDY GUIDE
Climate and Innovation: The Norse and the Aztecs, c. 790–1521 — the study guide
The complete revision document of the atlas: every chapter’s narrative, causes, turning point, consequences, discussion question with a full answer, and one verified interesting fact. Print it, annotate it, argue with it.
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CHAPTER 1 · c. 950–1450 · 1250
Climate as a Force in History
Medieval climate changed unevenly from place to place, which is why scientists call the warm spell an anomaly, meaning a regional departure from the usual pattern, much as one unusually hot summer stands out from the long-run average in a city’s records. Comparing hundreds of records in 2009, Michael Mann and his colleagues found that the years 950–1250 were warm around the North Atlantic while parts of the tropical Pacific were cool. In south Greenland, midge remains in the mud of Scoop Lake point to summers about 1.5 °C warmer between 900 and 1400 than in the colder centuries on either side. Yet lakes near Kangerlussuaq, further north and inland, record a fall of about 4 °C in some eighty years from around 1100. The cold returned abruptly, and Gifford Miller’s team dates its onset to 1275–1300, after a burst of volcanic eruptions whose sulphur dimmed the sun and whose effect spreading sea ice then prolonged. A coast could therefore be warm for one community while its neighbour cooled, and that unevenness is what turns climate into history.
Most of this knowledge comes from proxies, natural records that stand in for a thermometer in the way that a tree’s rings stand in for a calendar. At Summit, the highest point of the Greenland ice sheet, the American GISP2 team drilled 3,053 metres to bedrock between 1989 and 1993, and the European GRIP core reached 3,028 metres in 1992. Every year’s snow survives as a layer, and the share of a slightly heavier form of oxygen in it rises when the air is warmer, so the ice works like a thermometer that wrote down its own readings. Lake muds add rainfall, and tree rings add exact years, as when a burst of cosmic radiation recorded in the ring for 993 later dated Norse timber in Newfoundland. Written sources complete the picture, because Icelandic annals record ice and hard winters, and Mexica chronicles describe the frosts and droughts of the 1450s that Mexican tree rings now confirm. The strongest arguments come when ice, wood and words agree.
The two cases meet the same question from opposite directions, and the map is built to let a reader compare them. The Norse, the Scandinavian peoples of the Viking Age, were a mobile people who used the warm centuries to sail west, settling Iceland in the 870s and Greenland in the 980s and reaching North America around 1000, so their story tests whether farming at the climatic edge could survive the cold that followed. The Mexica, often called the Aztecs, stayed in one basin and engineered it, so their story tests how far dikes, aqueducts and raised fields could tame a lake prone to salt, flood and frost. Set side by side, they show that the size of a society, the variety of its food and the reach of its trade decided as much as any single invention.
WHY IT HAPPENED
Living at the margin magnifies small changes. A society that farms close to the limit of what its crops and animals can tolerate feels a small shift in climate as a large shift in harvests. Greenland’s Norse depended on enough summer warmth and moisture to grow the hay that fed their cattle through eight winter months, while the Mexica grew maize at about 2,240 metres, where an early autumn frost can kill a crop before it ripens. In both places a change of a degree or two decided whether a year was ordinary or desperate.
Ocean currents and sea ice shape the routes. The North Atlantic’s climate is carried by the sea as much as by the air, which matters enormously to a people who travel by ship. The cold East Greenland Current, drawn as the grey arrow, carries Arctic ice south along Greenland’s east coast and around Cape Farewell. When the climate cooled, that drift ice spread further and lasted longer each summer, blocking harbours, lengthening voyages and making the link between Greenland and Norway slower and riskier.
Volcanoes can tip a climate into a new state. Large eruptions inject sulphur high into the atmosphere, where it reflects sunlight and cools the world for several years. Gifford Miller’s team argued in 2012 that a cluster of four large eruptions in about fifty years, including the great eruption of 1257–58 later traced to Samalas in Indonesia, began the Little Ice Age between 1275 and 1300. Spreading sea ice then reflected more sunlight and kept summers cold long after the volcanic haze had cleared.
Societies build their own vulnerabilities. The same weather harms societies differently, depending on how many people they must feed, how varied their food is and how far their trade reaches. A colony of perhaps 2,000–2,500 people on the edge of the Arctic had little margin for a run of bad years, while a city of perhaps 200,000 drew on an empire but concentrated its people on one lake. Climate exposed these differences more than it created them, and that is why the same cold or drought could be survived in one place and fatal in another.
THE TURN
Summit, Greenland, 1 July 1993. On this day the GISP2 drill reached bedrock 3,053 metres below the summit of the Greenland ice sheet, completing a record of past climate that can be read almost year by year. This is the hinge of the chapter because it changed what historians could ask. Before the great cores, the climate of the Norse age was inferred largely from the sagas and annals whose story it was meant to explain, so the argument risked going in a circle. After them, climate became independent evidence that could be tested against the documents, and the documents tested against it.
WHAT IT CHANGED
The warm centuries open the sea road. The warmth of roughly 950–1250 coincided with the boldest phase of Norse voyaging, when settlers crossed open water to Iceland, Greenland and North America. The next chapter asks what made those crossings possible in the first place, and it finds the answer in a ship and in the farming society that paid for it, with climate as the setting that made the gamble of open-ocean sailing pay off more often than it failed.
The cold tests the farms. The shift into the Little Ice Age after about 1275–1300 fell hardest on the communities furthest out, above all the Greenland settlements that lived on hay, cattle and walrus ivory. Chapter 5 follows that test in detail and weighs climate against markets, isolation and choice as explanations of why the Norse left while the Inuit, newly arrived, stayed and prospered.
A second laboratory in Mexico. The same questions about margins, buffers and invention apply to the Basin of Mexico, where frost and drought struck in the 1450s and floods in 1449 and 1499. Chapter 8 shows how the Mexica answered with dikes, aqueducts and granaries, and how each answer, by letting more people live on the lake, created a new and larger kind of risk.
DISCUSSION QUESTION
Can climate ever be the cause of a society’s success or failure, or only its context?
The evidence in this atlas supports climate as a powerful context that becomes decisive only through a society’s structure. The warm centuries plainly widened the window for Norse farming in Greenland, and the cooling after 1275–1300 narrowed it, so a purely human account ignores real physical change. Yet the same cooling did not end Iceland, and the Thule Inuit expanded into Greenland during exactly the centuries when the Norse withdrew, which shows that the cold was survivable with the right tools and food. The proxies also disagree, since Lake 578 shows drying where the summit cores show cold. A careful answer treats climate as a pressure whose effect depends on population, trade, technology and choice, and historians call this the study of vulnerability. The transferable insight is that the same shock can be an inconvenience for one society and a catastrophe for another, so explanation must always ask who was exposed and why.
AN INTERESTING FACT
The principle behind ice-core thermometers began with beer bottles. On a rainy Saturday at the end of June 1952 the Danish physicist Willi Dansgaard set out an empty beer bottle with a funnel in his garden in Herlev, near Copenhagen, to catch the rain from successive showers, and found that the share of heavy oxygen in the water changed with the temperature of the cloud it fell from. If falling snow kept the same signature, he reasoned, the Greenland ice sheet would be an archive of past temperatures. Two decades later he read that archive beside the history of the Greenland Norse.
CHAPTER 2 · c. 790–900 · 866
The Ship and the Sea Road
The ship was the decisive invention because it changed what distance meant for people living along the North Sea. Archaeologists know it from boats buried as graves and wrecks sunk as barriers. The Oseberg ship, built around 820 and buried in 834, is 21.5 metres long and was rowed by fifteen pairs of oars; the Gokstad ship, built of timber felled around 890, carried thirty-two. Its overlapping planks flexed with the waves and absorbed their force, and its draft, the depth of hull below the waterline, was only about a metre, roughly waist height on an adult, so crews could beach it on any strand. By the eleventh century the warship Skuldelev 2, built near Dublin in about 1042, was 30 metres long and carried a crew of 65–70. A fleet like that could appear at a coast with almost no warning, and that surprise was the source of Norse power.
The ship also shows why innovation is a system, because each part depended on the farm behind it. Lise Bender Jørgensen calculates that the sail of a cargo ship needed well over 200 kilograms of wool and about ten years of work, and a warship’s sail more than 1.5 tonnes of wool and fifty to sixty years of labour, almost all of it by women. Iron for the rivets came from lumps of ore dug from bogs and smelted in charcoal furnaces, and the oak came from forests that took a century to grow. A single warship therefore embodied years of a farming community’s labour, which is why only chieftains who commanded many farms could launch fleets.
Raiding and trading grew together, which is why the map shows merchants’ routes beside war fleets, and both were driven by the search for wealth and status. James Barrett argues for a surplus of young unmarried men raiding to win the payment due to a bride’s family, and Ben Raffield, Neil Price and Mark Collard link this to polygyny, where a few powerful men had several wives, as some societies still permit today. Silver supplied the pull, since Scandinavian finds include hundreds of thousands of Islamic silver coins called dirhams, the dollars of the medieval trading world. When monks at Lindisfarne were killed or carried off in 793, the scholar Alcuin wrote from Charlemagne’s court that nobody had believed such a voyage from the sea possible. Yet the trading towns of Kaupang and Hedeby were thriving, and around 890 a chieftain named Ohthere told King Alfred of Wessex that he hunted walrus for their tusks and hides and collected tribute in furs from the Sámi, the herding and hunting people of the far north. Dublin, founded in 841, became a Norse town and York fell to a great army in 866, so the sea road built in war became a road for settlement.
WHY IT HAPPENED
A scarcity of farmland at home. Norway is mostly mountain, forest and rock, and only about 3 percent of its land can be cultivated, so good farms along the fjords were limited and passed to eldest sons. Younger sons and landless men needed another route to wealth. The ship gave them one, first by carrying them abroad to raid and trade, and later by carrying whole families to new land in the islands of the west, where a farm could be claimed by anyone willing to clear and defend it.
Silver from the Islamic world. In the ninth and tenth centuries the Abbasid caliphate and its neighbours minted silver coins in enormous numbers, and a great share flowed north through the rivers of Russia and across the Baltic in exchange for furs and slaves. Scandinavian finds of these dirhams now run to hundreds of thousands. This flood of silver gave chieftains the means to reward followers and made trading towns such as Hedeby rich, which in turn drew raiders toward wealth wherever it gathered.
Unguarded wealth across the North Sea. Christian monasteries in Britain and Ireland held gold, silver and books on coastal islands chosen for their solitude, and they had no defences against an attack from the sea. Kingdoms such as Northumbria were divided by civil wars, and the Frankish empire of Charlemagne’s heirs split after 840. The ship let Scandinavian crews pick targets where local power was weak, strike and be gone before an army could gather, so political division abroad multiplied the value of mobility.
A society organised for voyages. Norse society could raise the crews and materials that voyages required because chieftains commanded followers bound to them by gifts and oaths, much as a modern company commands employees with pay and loyalty. Farms produced the wool for sails, and assemblies settled the quarrels that would otherwise have kept men at home. The voyages abroad were therefore the overseas extension of institutions and loyalties that already worked at home, carried across the sea by men who expected to return richer.
THE TURN
Lindisfarne, 793. The raid on the monastery of Lindisfarne, off the coast of Northumbria, is the conventional start of the Viking Age, and it earns that place because it changed how Europe perceived the sea. Scandinavians had probably traded with Britain for decades, and the number of people killed was small beside later attacks. What changed was that the most learned men of Europe now understood that the sea, which had protected holy places, had become a highway for anyone with the right ship. From this moment, coastal Europe began to reorganise its defences around a threat that came by water.
WHAT IT CHANGED
Settlement follows the raiders west. Once the routes were known, raiders were followed by families seeking farms. Norse settlers took the Northern Isles, the Hebrides and the Faroe Islands in the ninth century, and the next step west, across 500 kilometres of open sea to an empty Iceland, came in the 870s. Chapter 3 follows those settlers into a volcanic island with no king and no native people.
Norse towns and kingdoms in Britain and Ireland. Within a generation, raiding had turned into rule over whole regions. Dublin became a Norse trading town from 841, York became the capital of a Norse kingdom after 866, and the Danelaw of the 870s and 880s placed eastern England under Scandinavian law. These places tied the Norse world into the economy of western Europe and gave it the markets and churches that later colonies would depend on.
Walrus ivory enters the story. Ohthere’s account shows that walrus tusks and hide ropes were already valuable goods in the 890s, traded from the far north to markets in the south. This luxury would later become the economic engine of the Greenland colony, whose hunters ranged far up its west coast for walrus. Chapter 4 shows how much a distant society can come to depend on a single export.
DISCUSSION QUESTION
Was the Viking expansion driven more by the ship or by the society that built it?
The ship was necessary, since without a seaworthy, shallow-drafted vessel no amount of ambition could have reached Lindisfarne, Dublin or Iceland. Yet similar ships existed in Scandinavia for a century before 793, which suggests that the technology waited on a reason to be used. The social evidence supplies that reason: scarce land, a surplus of young men without the means to marry, chieftains competing in silver and fame, and an inflow of Islamic coin. Lise Bender Jørgensen’s calculations also show the ship as a product of society, since one warship’s sail consumed decades of women’s labour that only a well-organised farming economy could spare. Historians still disagree about which social factor mattered most, partly because the written sources come from the victims and say little about Scandinavian motives. The transferable insight is that an innovation spreads when a society both can afford it and has a motive to use it, and either alone is not enough.
AN INTERESTING FACT
The grandest Viking ship burial yet found was made for two women. In 834 the Oseberg ship was hauled ashore beside the Oslo fjord and buried under a mound of turf with the bodies of two women, one probably in her seventies or eighties and the other about fifty. Around them lay a carved wagon, three sledges, beds, tapestries, kitchen tools and the bodies of horses and oxen. The clay of the mound sealed out the air, so the ship survived to be excavated in 1904, and it shows that the most honoured burial of the age could belong to a woman.
CHAPTER 3 · 870–1000 · 930
Iceland: A Society on a Volcanic Island
The settlement of Iceland was a planned migration of farmers, and its scale is now measurable from several directions. Landnámabók, the Book of Settlements, names nearly 400 leading settlers and about 1,400 places, and population geneticists estimate that some 8,000–16,000 people arrived in all. Ancient genomes, DNA read from the skeletons of the first settlers much as a modern ancestry test reads a living person’s, studied by Sunna Ebenesersdóttir’s team in 2018, show that the settlers were on average only about 57 percent Norse in ancestry, with most of the rest Gaelic, and earlier studies found that more than 60 percent of female lineages came from Ireland and Scotland. Many of these women and men came as slaves taken in raids, which means that the Gaelic west supplied much of the labour that built the new farms. The colony was therefore a Norse society with a mixed people at its foundation.
The settlers farmed as they had at home, and the island made them pay for it. Livestock lived on hay cut in summer and stored for winters that could last seven months, so every farm needed meadows, and barley grew only in the milder south and west. Birch woodland covered perhaps a quarter to two-fifths of the land when the settlers arrived, but cutting for fuel and building, and above all grazing by sheep that ate the seedlings, left less than 1 percent by the twentieth century. Without roots to hold it, the light volcanic soil was stripped by wind and water, and about 20,000 square kilometres of soil cover have probably eroded since settlement. Volcanoes added sudden shocks, as the volcano Hekla did around 1104 when its pumice buried the valley of Þjórsárdalur, so the Icelanders lived with a land that could change suddenly and that degraded slowly.
The Althing, Iceland’s national assembly, was the answer to a different problem, which was how to keep peace among armed farmers who acknowledged no king. Each June the chieftains, called goðar, who were part local lords and part elected representatives, much like the bosses of modern political parties, met at Þingvellir with their followers for about two weeks. There were 36 chieftaincies at first and 39 after a reform around 965, which also created four regional courts, one for each quarter of the island, and around 1005 a Fifth Court heard appeals. The lawspeaker, an elected official, recited one third of the law from memory every summer until the law was written down in 1117–18. Iceland therefore had procedure without enforcement, since victorious litigants had to carry out judgments themselves, and the system lasted for more than three centuries before civil war ended it in 1262–64.
WHY IT HAPPENED
An empty island within reach of the ships. Iceland lies about 970 kilometres west of Norway but only about 450 from the Faroe Islands, which Norse settlers had already reached, so the ship technology of Chapter 2 made the crossing practical. Irish hermits may have visited before the Norse, but no settled population existed, so newcomers could claim land without conquest. That emptiness made Iceland the first true Norse colony, a society built from scratch on land that no other people held.
Land hunger and politics in Norway. Later Icelandic writers explained the migration as flight from the tyranny of Harald Fairhair, who united much of Norway in the late ninth century. Historians treat that story with caution, because it flattered the settlers’ descendants, but scarce farmland and the growing power of kings do seem to have pushed ambitious families outward. Iceland offered the chance to be a chieftain answerable to no one, and the earliest settlers claimed vast estates that they later divided among followers and kin.
Captives from the Gaelic west. Norse raiding in Ireland and Scotland produced captives, and the settlers took many of them to Iceland as slaves to clear land, herd animals and weave cloth. The genomes show how large this element was. Without forced labour from the Gaelic world, the rapid clearing of a whole island within about sixty years would have been much slower, so violence abroad was built into the foundations of the new society.
The need for law without a king. Settlers who had left Norway partly to escape royal power still needed a way to settle quarrels over land, livestock and killings, which otherwise led to blood feuds that could destroy families. The answer was to borrow the Norwegian tradition of regional assemblies, called things, and to create one assembly for the whole island. The Althing grew out of this practical need for order among equals, and it was designed so that no single chieftain could dominate it.
THE TURN
Þingvellir, 930 — and the decision of 999/1000. The founding of the Althing at Þingvellir in 930 is the hinge because it gave a scattered population of farmers a single place and procedure for resolving conflict. Its value was tested around the year 1000, when Christian and pagan factions threatened civil war. Both sides agreed to let the lawspeaker Þorgeir decide, and after a day and a night under his cloak he ruled that all Icelanders should be baptised while some pagan practices might continue in private. A society without a king had found a way to make an enormous decision peacefully.
WHAT IT CHANGED
A springboard further west. Iceland became the base for the next voyages. Erik the Red, outlawed from Norway and then from Iceland for killings, sailed west in the early 980s and returned with plans for a new colony. Chapter 4 follows the fleet that left Iceland for Greenland in 985 or 986. Each new colony was founded by people who had lost out in the last one, so the frontier kept moving west.
A durable legal culture. The Althing sat almost every summer until 1798 and was revived in the nineteenth century, and Icelanders call it one of the oldest parliaments in the world. The tradition of law recited and later written in the Grágás law codes gave Iceland a sense of identity that outlasted its independence, which ended when the chieftains accepted the Norwegian crown in 1262–64.
An environment slowly degraded. The loss of woodland meant that Icelanders soon lacked timber for houses and ships and relied on driftwood and imports. Erosion reduced the grazing land just as the climate cooled after 1300. Iceland survived, unlike Norse Greenland, but it became poorer and more dependent on trade with Norway, and that slow pressure on a farming society frames the colder centuries of Chapter 5.
DISCUSSION QUESTION
Was the Althing a successful innovation if Iceland still fell into civil war and lost its independence in 1262–64?
Judged over three centuries, the Althing succeeded remarkably well. It resolved disputes among armed chieftains for more than 300 years without a king, an army or taxes, and its peaceful adoption of Christianity in 999 or 1000 shows that it could manage even a decision that divided society. Its weakness was the absence of enforcement, since winners of lawsuits had to carry out judgments with their own followers. As wealth and power concentrated in a few great families in the thirteenth century, those families fought the civil wars of the Sturlung Age and finally accepted the Norwegian king. The Althing’s failure was therefore a failure to adapt to changing inequality, which no medieval assembly anywhere had solved, and the institution itself survived as a symbol and later as a parliament. The transferable insight is that institutions which depend on rough equality among participants become fragile when that equality disappears.
AN INTERESTING FACT
When the first settlers reached Iceland, the only land mammal living there was the arctic fox, which had probably crossed on sea ice at the end of the last Ice Age. Every sheep, cow, horse, goat, pig, dog and cat on the island arrived in Norse ships, and mice came with them as stowaways. The settlers’ animals therefore met plants that had never been grazed by anything larger than a goose, which helps explain why the birch woods and thin volcanic soils gave way so quickly once the farms were built.
CHAPTER 4 · 985–1050 · 1021
Greenland and Vinland
The Greenland colony was designed around hay, and its geography followed the meadows. The settlers built about 500 farms in the Eastern Settlement and perhaps 75–100 in the Western, most of them deep inside the fjords where summers were warmest and grass grew best, away from the cold fog of the outer coast. At its peak around 1200 the colony probably held about 2,000–2,500 people, though older estimates ran to 5,000. A farm’s wealth was measured in the number of cattle its byres, the stone-and-turf cattle sheds, could keep alive through eight winter months, so the whole community depended on the summer’s hay harvest. Erik’s own farm, Brattahlíð, stood at the head of a fjord on the best land, which is how leadership and good meadows came to coincide.
Walrus ivory gave the colony an export that farming could not. Each summer, men rowed and sailed some 800 kilometres north to Norðrseta, the hunting grounds around Disko Bay, and brought back tusks, hides for rope and sometimes polar-bear skins. Ancient DNA studied by Bastiaan Star and James Barrett shows that by the twelfth century almost all the walrus ivory reaching Europe came from Greenland, carved into chess pieces, crosses and book covers. In return the Greenlanders bought iron, timber, grain and church goods. This trade made a tiny colony part of Europe’s luxury economy, though it also tied the colony’s prosperity to the taste of distant buyers.
Vinland was the furthest reach of this expansion, and the evidence for it combines saga and spade. The sagas describe Leif Eriksson finding a land of grass, salmon and mild winters, and later expeditions trading and fighting with people they called Skrælings, a dismissive Norse word for the Indigenous inhabitants, probably ancestors of the Innu or Beothuk of Labrador and Newfoundland. In 1960 Helge Ingstad and Anne Stine Ingstad found the site at L’Anse aux Meadows, with eight buildings for perhaps 70–90 people. Butternuts found there grow no closer than New Brunswick, so the Norse explored at least into the Gulf of St Lawrence. In 2021 Margot Kuitems and colleagues dated three pieces of cut wood to 1021 from the cosmic-ray signal of 993, preserved 29 rings inside the bark. The site was occupied for only a few years, which shows that a colony of a few thousand could reach America but not stay there.
WHY IT HAPPENED
Warm summers greened the southern fjords. The colony’s timing fits the Medieval Climate Anomaly, when midge remains from Scoop Lake near the Eastern Settlement indicate summers about 1.5 °C warmer than in the centuries before and after. Warmer, longer summers allowed enough hay to grow at the heads of the fjords to keep cattle alive through the winter. Erik the Red was exploiting a climatic window that he could not have understood in those terms but could see in the grass.
Iceland was already full and divided. By the 980s Iceland’s best land had been claimed for two or three generations, and younger sons and newcomers found few opportunities. Feuds also drove men out, since Erik himself was outlawed twice for killings. Greenland offered empty grassland to people who had lost out in Iceland, and the 25 ships that sailed in 985 or 986, carrying perhaps several hundred people with their animals, show how many were willing to gamble.
A name chosen to attract settlers. According to the Icelandic sources, Erik called the new land Greenland because people would be more willing to go there if it had an attractive name. The story shows that founding a colony required persuasion as well as seamanship, much as a modern developer markets a new town. Erik needed enough families to make the settlement viable, and the name was part of his recruitment, as were the best meadows he kept for himself at Brattahlíð.
European demand for walrus ivory. Walrus ivory was valued in Europe for carving religious objects and games, especially when African elephant ivory was scarce. Greenland’s walrus grounds in Norðrseta offered a supply that no one else could reach, and ancient DNA shows that by the twelfth century almost all European walrus ivory came from there. This demand gave the colony a reason to exist beyond subsistence and paid for the imports its farms could not produce.
THE TURN
L’Anse aux Meadows, 1021. The cutting of timber at L’Anse aux Meadows in 1021 is the hinge of this chapter because it marks the furthest point the Norse system could reach and the moment it began to pull back. Europeans and Indigenous Americans met across the Atlantic five centuries before Columbus, which proves that the ship and the settler society of the North Atlantic were capable of reaching a new continent. The withdrawal within a few years shows the limit of that capability. Reach depended on technology, while staying depended on numbers, supply and the consent of the people already there.
WHAT IT CHANGED
A colony locked into hay and ivory. With Vinland abandoned, Greenland’s economy settled into its long pattern of cattle and sheep on the fjord meadows, seals and caribou for food, and walrus hunting in the north for export. That combination worked for about three centuries, but it depended on summers warm enough for hay and on European demand for ivory, and Chapter 5 shows both beginning to fail after 1250.
Timber trips to Markland continue. The Greenlanders kept sailing to Markland, probably the forested coast of Labrador, for the timber that their treeless land lacked. Icelandic annals for 1347 record a small Greenland ship, crewed by 17 or 18 men, that had been to Markland and was driven by storms to Iceland. The contact with America therefore did not end in 1021, though it never again became settlement.
Greenland enters the Church and the crown. The colony grew into a recognisable part of Christian Europe. It received its own bishop at Garðar in 1126 and built about fourteen to seventeen churches, and in 1261 it accepted the authority of the Norwegian king. These ties brought priests, ships and goods but also made the colony dependent on decisions taken in Bergen and Trondheim, as Chapter 6 explains.
DISCUSSION QUESTION
Does the abandonment of Vinland show the limits of Norse innovation or the limits of Norse numbers?
The evidence points more strongly to numbers than to technology. The ships, seamanship and building skills on display at L’Anse aux Meadows were fully capable of crossing to America, repairing vessels there and housing 70–90 people through a winter, so their inventions were equal to the task. The limit was population, since Greenland itself held perhaps 2,000–2,500 people, too few to settle and defend a distant colony. The sagas also show that Indigenous peoples were numerous, organised and willing to fight, and that the Norse held no decisive advantage in weapons. Distance multiplied every one of these weaknesses. Historians who stress conflict and those who stress logistics are describing the same problem from two sides, since a larger colony could have absorbed both the losses and the long voyages. The transferable insight is that the reach of a technology can far outrun the size of the society using it, and expansion stops where numbers run out.
AN INTERESTING FACT
According to the Saga of the Greenlanders, the first child of European parents born in the Americas was a boy named Snorri, born in Vinland to Gudrid Thorbjarnardóttir and her husband Thorfinn Karlsefni around 1010. The family returned to Iceland and farmed in the north, and the saga says that Gudrid, widowed, later made a pilgrimage to Rome before becoming a nun. The saga traces several Icelandic bishops among her descendants. Gudrid had travelled from Iceland to Greenland, Vinland, Norway and Rome, which makes her one of the most widely travelled people of her century.
CHAPTER 5 · 1250–1450 · 1408
Living with the Cold
The Norse met the cold first by changing what they ate, which shows that they were adapting. Bones carry chemical signatures, called isotopes, that record whether a person’s protein came from land or sea, much as a till receipt records what a shopper bought, and Jette Arneborg’s team found that Norse diets shifted from about 20 percent marine food at settlement to about 80 percent by the end. A later study with 123 skeletons revised the early figure to 15–50 percent and showed the 50 percent mark being crossed in the late thirteenth century. Rubbish heaps tell the same story, since seal bones make up 30 to over 80 percent of the animal remains on Greenland farms, mostly harp and hooded seals caught in communal hunts on their spring migration. A people supposedly too proud to eat seafood was, in practice, living largely on seals.
The colony’s economy weakened at the same time as its climate. Lake 578 near Brattahlíð shows a drying trend that would have cut the hay crop, and closely spaced bad years forced farmers to slaughter animals they could not feed. James Barrett’s study of walrus skulls shows the hunters taking smaller animals, often females, from ever further north, a sign that the nearer herds had been depleted. Europe was also turning back to elephant ivory, and the plague pandemic called the Black Death, which reached Norway in 1349, killed perhaps half or more of its people, shrinking the market. The royal trading ship that served Greenland sank in 1369 and was not replaced, so the colony grew poorer and more isolated in the very decades when it most needed contact.
The Thule Inuit, ancestors of today’s Greenlanders, arrived with a different solution to the same environment. Moving east across Arctic Canada in the thirteenth century, they reached Smith Sound and Greenland’s far north, Disko Bay by the fourteenth century and the south by the later fourteenth. Their toggling harpoon, whose head twisted sideways inside a seal, let them hunt at breathing holes in winter ice, which the Norse never mastered. The Icelandic annals record for 1379 that Skrælings, the Norse name for the Inuit, killed eighteen Greenlanders and enslaved two boys, though the entry survives only in later copies. The Western Settlement was found empty around 1360, and the last written record of the Eastern Settlement is a wedding at Hvalsey church in 1408. Radiocarbon dates, which measure the slow decay of carbon in once-living material like a clock that starts at death, keep the Norse there until about 1430 on the evidence of grave clothes, and they were gone by the late 1400s, while the Inuit remained. The people who brought tools for sea ice outlasted the people who brought cattle.
WHY IT HAPPENED
Cooler and drier summers cut the hay. The Little Ice Age began abruptly between about 1275 and 1300 and intensified again between 1430 and 1455, according to Gifford Miller’s team. In south Greenland the clearest signal at Lake 578 is drying, which would have reduced the hay harvest even without much cooling. Because cattle needed stored hay for eight months, a few bad summers in a row forced culls that took years to rebuild, and the farms’ margin of safety shrank.
Drift ice lengthened and endangered voyages. More summer drift ice along east and south Greenland made the passage from Iceland and Norway slower and more dangerous, and a late-medieval sailing guide claims the old route had been abandoned because of ice, though that sentence may be a later addition. Fewer ships meant less iron, timber and grain, and fewer chances for young people to leave or for new settlers to arrive, so isolation compounded every other pressure.
The ivory economy weakened. Walrus ivory paid for the colony’s imports, but by the fourteenth century the hunters were taking smaller animals from further away, and Europe was again importing elephant ivory from Africa. In 1327 a cargo of about 520 tusks, paid as church dues, was still worth roughly as much as 780 cows, so the trade remained valuable while becoming less reliable. A colony with one export was exposed to every change in its buyers’ tastes.
Plague and isolation in Norway. The Black Death reached Norway in 1349 and killed perhaps half or more of the population, shrinking the market for luxuries and the shipping that served the colonies. Bergen’s merchants turned to the profitable trade in dried cod, and the royal trading ship to Greenland was not replaced after it sank in 1369. Greenland’s link to Europe thinned just as its own economy weakened, and a colony that could no longer trade could no longer replace its iron tools.
THE TURN
Hvalsey church, 16 September 1408. On this day Þorsteinn Ólafsson and Sigríður Björnsdóttir were married in the stone church at Hvalsey, an event recorded because the couple later needed proof of the marriage in Iceland. It is the hinge of the chapter because it is the last written evidence of Norse Greenland, and after it the story can be told only through archaeology. The wedding also shows a community still functioning, with priests, a church and legal documents, only a generation before the end. That combination, normal life followed by silence, is why historians now speak of departure more often than of catastrophe.
WHAT IT CHANGED
Greenland becomes Inuit land. By about 1500 the Inuit lived along most of Greenland’s west and south coasts, including the old Norse districts, and their descendants make up most of Greenland’s population today. On the map, the blue zones that step down the coast after 1300 represent this expansion. The Norse experiment had been replaced by a society far better equipped for the Arctic.
A debate that shaped modern environmental history. The fate of Norse Greenland became a classic case study for arguments about climate change and collapse, most famously in Jared Diamond’s book of 2005. The archaeological response has made the colony an example of adaptation under compounding pressures, a model now applied to many societies facing climate change, including the Mexica in the second half of this atlas, whose lake city faced flood, frost and drought.
Europe forgets and then searches. Norway lost contact with Greenland in the fifteenth century, and Europeans gradually forgot where the colony had been. When Danish and Norwegian rulers took renewed interest, they assumed the Norse descendants might still survive, which led to new voyages in the sixteenth to eighteenth centuries and eventually to the Danish colonisation of Greenland from 1721, discussed in the epilogue. The Skálholt map, drawn in Iceland around 1570, shows how much of that geography survived only in written memory.
DISCUSSION QUESTION
To what extent were the Greenland Norse victims of the Little Ice Age?
The cold was a real pressure, but the evidence suggests it was decisive only in combination with economic decline and isolation. Cooling and drying reduced the hay harvest, and more drift ice made voyages harder, so the climate narrowed the colony’s margin. Yet the Norse adapted, eating mostly seal by the end, and the Inuit expanded into Greenland during the same cold centuries, which shows that the environment could support people with the right technology. The collapse of the ivory trade, the plague in Norway and the end of regular shipping removed the income and contact that had made a small European colony viable. Most scholars, following Dugmore and colleagues, therefore describe a conjuncture of pressures acting on a society too small to absorb them. The orderly abandonment of farms suggests that many people chose to leave. The transferable insight is that climate change often works slowly, exhausting a society’s alternatives one by one until leaving becomes the sensible choice.
AN INTERESTING FACT
One of the most famous garments from Norse Greenland was misdated by two centuries. In 1921 the archaeologist Poul Nørlund excavated the churchyard at Herjólfsnes, where the permafrost had preserved woollen gowns, hoods and caps. One tall cap, cut in a style resembling fashions at the fifteenth-century Burgundian court, was taken as proof that Greenlanders were still following European fashion after 1500. Radiocarbon dating later placed it between about 1280 and 1380, while other grave clothes from the same churchyard dated to about 1430, which is the latest firm evidence of Norse people in Greenland.
CHAPTER 6 · c. 1100–1450 · 1450
What the Norse Left
The ship tradition lasted because the same design served war, trade and fishing. After the age of raids, the same clinker technique of overlapping planks produced cargo vessels like Skuldelev 1, a 16-metre ocean-going ship of pine built in western Norway around 1030, and later the broad trading ships that carried fish and grain. Boatbuilders along the Nordic coasts kept the method alive into the twentieth century, and in 2021 UNESCO recognised Nordic clinker boat traditions as part of the world’s intangible heritage. A technique that could be scaled up or down and adapted to any cargo survived every change in politics and climate, since some boat was always needed.
The stockfish trade shows how an economy could adapt to a colder North Atlantic. Fishermen around the Lofoten islands, at the market of Vágar, caught spawning cod each winter and dried them on racks in the cold, dry wind, producing food that could travel for years without salt. Archaeologists led by James Barrett have found a sudden rise in sea fish bones on English sites around the year 1000, a change they call the fish event horizon, and chemical testing of cod bones links part of this trade to Arctic Norway. By the fourteenth century German merchants of the Hanseatic League, a federation of trading towns that worked much like a modern trade bloc, ran a permanent office at Bergen from about 1360. Christian Keller estimates that a cargo of walrus tusks shipped from Greenland in 1327 was worth nearly 60 tonnes of stockfish, which shows which commodity was becoming the real currency of the north.
Greenland’s failure was the price of specialisation, and comparing it with Iceland makes the point. Both colonies were Norse, Christian and subject to Norway after the 1260s, and both suffered the colder centuries. Iceland, with perhaps 40,000–60,000 people around 1100, estimated from a count of 4,560 tax-paying farmers, could sell stockfish and wool and absorb bad years, and it survived plague, volcanoes and poverty. Greenland, with a twentieth of that population, depended on hay and ivory, both of which failed together. The Church linked the colony to Europe through its bishop at Garðar, appointed in 1126, and the archbishopric of Niðaróss from 1153, a church province run from Trondheim much like a regional headquarters, but such ties were only as strong as the shipping that carried them. The surviving Norse world was the part that could feed itself from the sea and sell what it caught.
WHY IT HAPPENED
Versatile technology survives changing purposes. The clinker ship survived the end of raiding because it was a general-purpose technology, a tool like the modern lorry that serves many trades at once. The same method built warships, cargo ships and fishing boats in sizes from rowing boats to 30-metre vessels. When raiding ended, the ships found new work carrying fish, timber and grain, so the investment in shipbuilding skills, timber and wool never became obsolete. Its flexibility worked as a kind of insurance against change.
Cod suited a colder sea. The cooling of the North Atlantic harmed farms on the edge of their range but did not harm cod, which thrive in cold water and gather to spawn off Lofoten each winter. Air-drying in cold, dry wind preserved the catch without salt, which was expensive in the north. The stockfish trade therefore turned the northern climate into an advantage, a rare case in which colder conditions favoured an existing industry.
Iceland’s size and variety gave it resilience. Iceland’s population of perhaps 40,000–60,000 around 1100 and its mix of livestock, fishing and trade allowed it to absorb disasters that would have ended a smaller colony. Even the plague of 1402–04 did not end the society. Older estimates say it killed half or more of Iceland’s people, while recent studies put the toll nearer a quarter to 45 percent. Size and variety acted as insurance, spreading each loss across many farms and trades, which Greenland, with a twentieth of the population, never had.
Greenland depended on one export and one link. Greenland’s imports of iron, timber and grain were paid for almost entirely with walrus ivory and carried by a few ships from Bergen. When European buyers turned back to elephant ivory and the royal ship sank in 1369 without replacement, both the income and the link failed at once. Dependence on a single product and a single route left the colony with no fallback when conditions changed, however hard its people worked.
THE TURN
Bergen, c. 1360. The founding of the Hanseatic League’s permanent office at Bergen around 1360 is the hinge of this chapter because it shows where the Norse North Atlantic economy was heading. The future lay in bulk trade in a staple food, dried cod, managed by German merchants with access to the large markets of the Baltic and the North Sea. Greenland, with its luxury export and its long, icy route, had no place in that system. The same decades that made Bergen a great fish market saw the last royal ship sail for Greenland.
WHAT IT CHANGED
Norway becomes a fish economy. For the next five centuries the stockfish of northern Norway, shipped through Bergen, remained one of the country’s largest exports, and the wooden merchant houses of Bryggen still stand as a UNESCO World Heritage site. The trade showed how a northern society could profit from the cold, a contrast with Greenland’s defeat by it, and it tied Norway’s fortunes to German merchants for centuries.
Iceland endures as a fishing and farming society. Iceland passed under Norwegian and then Danish rule and grew poorer in the colder centuries, but it survived with its language, law codes and saga literature intact. Its manuscripts, including the sagas that preserve the Vinland voyages, became the chief source through which later Europeans learned of the Norse Atlantic, and that literary survival is itself a legacy of the Althing’s culture.
A second experiment begins far to the south. While the last Norse farms in Greenland emptied, the Mexica of central Mexico were completing an empire built on the opposite strategy: one dense, engineered landscape fed by tribute from a wide region. Chapter 7 turns to that second case, which tests whether concentration and engineering could do better than mobility and dispersal against a demanding environment. The comparison makes each case clearer than either would be alone.
DISCUSSION QUESTION
Which Norse innovation was most significant in the long run: the ship, the stockfish trade or the Althing?
Each can claim significance, and the answer depends on what significance measures. The ship made everything else possible, carrying settlers to Iceland and Greenland and later carrying the fish and grain on which the North Atlantic economy depended, and its building tradition survived into the twentieth century. The stockfish trade had the greatest economic weight after about 1100, turning a cold sea into a lasting export and binding Norway to the markets of England and the Hanseatic towns. The Althing mattered most for identity and political culture, giving Iceland a tradition of law and assembly that outlived independence and shaped its modern parliament. A strong answer might argue that the ship was the enabling condition while the stockfish trade was what actually sustained Norse societies through the colder centuries. The transferable insight is that the most significant innovations are often those that keep finding new uses after their original purpose has gone.
AN INTERESTING FACT
The most famous objects made from Greenland’s exports were found on a beach in the Outer Hebrides. In 1831 a hoard of 93 carved pieces turned up near Uig on the Isle of Lewis: 78 chessmen, 14 round playing pieces and a belt buckle, carved around 1150–1200 mostly from walrus ivory and some whale teeth, and probably made in Trondheim. The pieces include kings, queens, bishops and warders biting the tops of their shields. Eighty-two are in the British Museum and eleven in National Museums Scotland, and much of their ivory may have come from the hunting grounds of Norðrseta.
CHAPTER 7 · 1325–1428 · 1428
An Empire Built on a Lake
The Basin of Mexico was both rich and demanding, which is why the people who lived there had long experimented with water. The basin covers somewhere between 7,500 and 9,600 square kilometres, depending on where its rim is drawn, and its lakes merged into one sheet in wet years and shrank into separate bodies in the dry season. Rain fell mainly between June and September, so a late start or an early frost could destroy the maize harvest. Lake Texcoco, at the bottom of the basin, gathered salts that evaporation left behind, while springs at the foot of the southern mountains kept Xochimilco and Chalco fresh. Communities around the shores had already begun building chinampas, raised fields piled up from the bed of the shallow fresh lakes like garden beds standing in water, by the time the Mexica arrived. The newcomers therefore inherited a tradition of water engineering along with its problems.
The Mexica story of their own origins explains why they ended up on the least promising land. Their chronicles describe a long migration from a homeland called Aztlan, a stay at the springs of Chapultepec in the late thirteenth century, expulsion by stronger neighbours around 1299 or later, and service to the town of Culhuacan before a violent break with their hosts drove them into the marshes. Tradition places the founding of Tenochtitlan in the year Two House, 1325, named in the Mexica calendar that combined numbers and signs, and the Codex Mendoza, a painted book made by Indigenous artists for the Spanish viceroy after the conquest, opens with that scene, an eagle on a cactus at the centre of an island divided by canals. Kinsmen founded Tlatelolco on a neighbouring island around 1337. These accounts were reshaped by later rulers, but they agree that the Mexica began as poor outsiders who had to make marginal land work.
The lake set the terms of Mexica power for a century. The islands could be defended against armies and reached by canoe from every shore, and the lake supplied fish, waterfowl, insects, salt and an edible green alga, so a growing population could eat without much farmland. Yet the islands had no springs, and drinking water came by canoe from Chapultepec until a flimsy channel of clay and reeds was built under the ruler Chimalpopoca in the 1420s. The Mexica paid tribute, a tax in goods and labour, to Azcapotzalco and fought in its wars, and when its ruler Maxtla turned against them, the ruler Itzcoatl allied with Nezahualcoyotl, the exiled heir of Texcoco, and the Tepanec town of Tlacopan. Their victory in 1428 created the Triple Alliance, a partnership of three cities to share conquest and tribute, much like a joint company with three shareholders, and handed the Mexica the lake and its shores, so a people who had fled into the marsh now controlled it.
WHY IT HAPPENED
A closed basin made salt and floods inevitable. Because the Basin of Mexico had no river leading out of it, every drop of rain that fell on the surrounding mountains ended in the lakes and left only by evaporation. That simple fact made Lake Texcoco salty and meant that wet years raised the water level across the whole system. Any society that settled on the lake inherited these two problems, which would shape Mexica engineering for the next century.
Latecomers took the marginal land. When the Mexica arrived in the basin in the thirteenth century, the best farmland around the shores already belonged to established city-states such as Azcapotzalco, Culhuacan and Texcoco. Driven from Chapultepec and then from Culhuacan, they took refuge on islands in the western marshes that nobody else wanted. Their later empire grew from a position of weakness, which helps explain why they prized military service and organised labour so highly.
Service to Azcapotzalco taught war and politics. For about a century the Mexica fought as mercenaries for the Tepanec kingdom of Azcapotzalco and paid it tribute, campaigning for its rulers across the basin. This service gave them military experience, marriage ties with powerful families and a model of how a dominant city could collect tribute from others. When the Tepanec kingdom split after its ruler Tezozomoc died in 1426, the Mexica were ready to turn those lessons against their overlords.
An alliance of the threatened. Maxtla, the new ruler of Azcapotzalco, threatened both the Mexica and Nezahualcoyotl, whose father had been killed by the Tepanecs in 1418, and some Tepanec towns such as Tlacopan opposed him too. Their shared danger made cooperation possible among cities that had often been rivals. The Triple Alliance grew from a coalition of the threatened, much as modern alliances often form against a common enemy before they become instruments of expansion.
THE TURN
The fall of Azcapotzalco, 1428. The sack of Azcapotzalco in 1428 is the hinge of this chapter because it turned the Mexica from vassals into masters of the lake. The victory gave Tenochtitlan, Texcoco and Tlacopan the lands and tribute of the Tepanec kingdom and the authority to organise labour across the basin. That authority mattered as much as any territory, since the great water projects of the next decades, dikes, aqueducts and new chinampas, required thousands of workers drawn from many towns. Political power over the lake came first, and engineering of the lake followed.
WHAT IT CHANGED
A Triple Alliance to share tribute. Tenochtitlan, Texcoco and Tlacopan agreed to campaign together and to divide tribute, with the two larger partners taking two-fifths each and Tlacopan one-fifth, according to the later chronicles. Within a few years the alliance had subdued the southern lake towns of Xochimilco and Cuitlahuac, giving it control of the best chinampa land in the basin and the labour of the towns that farmed it.
Engineering the lake becomes possible. With the shores in friendly hands, the alliance could mobilise labour from many towns to rebuild the city’s water supply and protect it from floods. Chapter 8 follows Nezahualcoyotl’s great dike of about 1449 and the masonry aqueduct from Chapultepec, both of which depended on the political power won in 1428 to call up workers from towns all round the lake.
Expansion beyond the basin. By defeating Azcapotzalco, the alliance also inherited its tribute networks outside the basin. Under Itzcoatl and his successor Moctezuma I the alliance began campaigning south into Morelos and north into the Otomí lands, building the tribute empire that would later feed Tenochtitlan with maize, beans and cloth from hundreds of kilometres away, and that would one day make the alliance many enemies.
DISCUSSION QUESTION
Was the lake more of an advantage or a burden to the Mexica in their first century?
In the short term the lake was mostly an advantage. It protected a weak migrant people from stronger neighbours, fed them through fish, birds, algae and salt, and gave them canoe transport in a land without draught animals, so a population could grow on islands with little farmland. Its burdens were real from the start, since the islands lacked springs and the closed basin brought salt and floods. During the century of Tepanec rule those burdens were manageable because the city was small and its rulers could not command large labour forces. Once the victory of 1428 gave them power over the shores, the Mexica chose to grow the city and engineer the lake, which made its advantages larger and its dangers more serious. The transferable insight is that a resource and a risk are often the same feature of a landscape, and the balance between them depends on how many people come to rely on it.
AN INTERESTING FACT
The Codex Mendoza, the richest painted source on the Mexica, owes its survival to piracy. On its way to Spain the manuscript was captured, according to Samuel Purchas, by French privateers and passed to André Thevet, cosmographer to the king of France, who signed it in 1553. The English geographer Richard Hakluyt later bought it in Paris, and Samuel Purchas published woodcuts of its pages in 1625. It then passed to the scholar John Selden and entered the Bodleian Library in Oxford with his books in the 1650s, where it remains as MS. Arch. Selden. A. 1.
CHAPTER 8 · 1428–1500 · 1499
Water: Dikes, Aqueducts and Floods
The dike, a flood barrier across the lake, was the alliance’s answer to the basin’s two great hazards, flood and salt, and it shows how political power became engineering power. The chroniclers say that Moctezuma I asked Nezahualcoyotl to design it after several wet years, usually dated to 1449, raised the lake over the city. Workers from Tlacopan, Culhuacan, Iztapalapa, Tenayuca and Xochimilco built a wall of stone and clay, faced on both sides with densely driven stakes, from Atzacoalco to Iztapalapa. Later writers assumed it had gates to let water through, though Josefina García Quintana and José Rubén Romero Galván found no evidence for them. By blocking the salty water of eastern Lake Texcoco, the dike turned the western part into a fresher lagoon, the Lake of Mexico, where new chinampas, raised fields built up from the lake bed like garden beds in water, could be built.
Drinking water was a separate problem, because the island had no springs of its own, so it depended on an aqueduct, a channel carrying spring water from the shore like a modern water main. A first channel of clay and reeds from Chapultepec, built in the 1420s, kept failing, so Moctezuma I ordered a better one, again with Nezahualcoyotl’s advice, begun around 1454 and working by 1466. Its channels of tightly packed earth and mortar ran beside the causeway from Tlacopan, and Spanish observers later noted that the water ran in one channel while the other was cleaned. From the city’s edge, the water was carried by canoe and sold. The aqueduct and the dike were political monuments as much as utilities, since only a ruler who could summon thousands of workers from many towns could build them.
The years after 1450 showed both what engineering could not prevent and what it could cause. The chronicles describe years of rain, hail and early frosts followed by drought, and the Mexican Drought Atlas, built from tree rings, confirms a great drought in 1452–54. In 1454, the year named One Rabbit in the Mexica calendar, people sold themselves or their children to the Totonacs of the Gulf coast in exchange for maize, and Moctezuma I opened the royal granaries. The disaster pushed the alliance to conquer the warm, wet Gulf lowlands for a reliable food supply. In 1499 Ahuitzotl ignored the warnings of Tzotzomatzin, ruler of Coyoacán, who was killed for them, and brought the powerful spring of Acuecuexco into the city. The water broke out and flooded Tenochtitlan until divers sealed the spring, which shows how a system grown more ambitious had also grown more dangerous.
WHY IT HAPPENED
Floods drowned the growing city. Because the Basin of Mexico had no outlet, a run of wet years raised the lake across the islands, and the chronicles report such a flood around 1449. A small village could move, but a city of tens of thousands with temples and palaces could not. The scale of the investment in the island forced its rulers to protect it, which is why the dike was built after, and because of, the city’s growth.
Salt water limited the farms around the city. The lagoon around Tenochtitlan was part of salty Lake Texcoco, which made it poor for chinampas, since crops cannot grow in brackish water. Separating the western lagoon from the salty east promised fresher water that could be farmed, so the dike was an agricultural project as well as a flood defence. Its success opened the way for chinampa expansion in the decades after 1449, close enough to the city for produce to arrive fresh by canoe.
An island without springs needed piped water. Tenochtitlan’s people drank water carried from the springs of Chapultepec on the western shore, which became impossible to supply by canoe alone as the population grew. The first aqueduct of clay and reeds failed repeatedly. A reliable channel was therefore essential to any further growth, and the second aqueduct, working by 1466, made a much larger city possible, with fountains in the palaces and water sold from canoes in every district.
Power over many towns supplied the labour. Great waterworks needed thousands of workers, stone quarried leagues away and timber for stakes, which no single town could provide. The victory of 1428 gave the Triple Alliance the authority to call on labour from towns around the lake, from Tlacopan to Xochimilco. Hydraulic engineering in the basin was therefore a product of empire, much as modern dams depend on states able to raise large sums and workforces, and the works in turn advertised the alliance’s power.
THE TURN
Nezahualcoyotl’s dike, c. 1449. The building of the dike is the hinge of this chapter because it changed the lake itself. Before it, the people of the basin adapted to the lake as nature made it; after it, the western lagoon was a managed body of water, fresher and protected, that could be farmed and built upon. On the map, the lagoon turns from pale salt to blue-grey fresh water in the snapshot of 1449. That transformation enabled the expansion of chinampas and the growth of the city in the next seventy years, and it committed the Mexica to maintaining an artificial environment.
WHAT IT CHANGED
Fresher water allows new chinampas. With the western lagoon freshened, new chinampas spread around the island and south toward Iztacalco and Mexicaltzingo, where the map shows fields in the lagoon after 1469. More land under cultivation close to the city supported more people, and Chapter 9 follows how chinampas, tribute and markets together fed a city of perhaps 200,000 people. Engineering and farming had become a single system.
Food security drives conquest. The famine of 1450–54 taught the Mexica that the basin alone could fail them, and the following years brought campaigns toward the warm, rain-fed Gulf coast, including Cuetlaxtlan, from which tribute in food and cotton flowed. Imperial expansion became, in part, an insurance policy against the climate of the high basin, as the tribute provinces painted tan on the empire map show, stretching to both coasts by 1500.
An engineered lake becomes a trap. The dike, causeways and aqueducts made Tenochtitlan dependent on structures that an enemy could seize or cut. In 1521 Spanish brigantines broke through the dike and Cortés’s allies cut the Chapultepec aqueduct, turning the engineered lake against its builders, as Chapter 11 explains. The more completely the city relied on built structures, the more an enemy could do by seizing a few of them.
DISCUSSION QUESTION
Did the Mexica control their environment, or did their engineering simply increase the risks they faced?
The evidence supports both claims, and the tension between them is the point. The dike reduced flooding and freshened the lagoon, the double-channel aqueduct supplied reliable drinking water, and royal granaries cushioned the famine, so in ordinary years the Mexica controlled the lake far better than their predecessors. Yet the famine of 1450–54 showed that frost and drought could not be engineered away, and the Acuecuexco flood of 1499 showed that ambition could overreach the limits of a closed basin. Engineering also allowed the city to grow, which meant that any failure would harm more people. Historians of risk call this the safe-development paradox, in which protection encourages concentration that raises the cost of a disaster. A balanced judgement is that the Mexica achieved real control within limits they did not fully understand. The transferable insight is that successful adaptation often raises a society’s exposure to the shocks it has not planned for.
AN INTERESTING FACT
The famine of 1454 left two phrases in the Nahuatl language. The year’s name in the Mexica calendar was Ce Tochtli, One Rabbit, and the sources describe the people of that year as having been “rabbited”, necetochuiloc, an expression for suffering famine. They also say that the people “became Totonacs”, because so many fled to the Totonac lands of the Gulf coast, or were sold there, in search of maize. A calendar date and the name of a neighbouring people had become words for hunger and flight, so that the language itself carried the memory of a climate disaster.
CHAPTER 9 · c. 1430–1519 · 1515
Chinampas: Feeding a City
The chinampa, a raised field built up from the lake bed like a garden bed standing in water, was an innovation in soil and water management, refined over centuries before the Mexica took control of it. Farmers dug canals by hand in the shallow southern lakes and piled the mud and plant matter into long rectangular beds, held in place by stakes and by willows called ahuejotes whose roots bound the edges. Seedlings were raised in nurseries of mud cut into small blocks and then transplanted, so a field could grow several crops a year. Studies summarised by José Luis de Rojas and Juan José Batalla estimate maize yields of about 3,000 kilograms per hectare on chinampas, against 1,000–1,400 on ordinary fields. The water also moderated temperatures, reducing the risk of frost that threatened rain-fed maize, so the chinampa answered the basin’s chief climatic hazard directly.
The Mexica state turned an older local technique into a regional system. The alliance conquered Xochimilco around 1430 and Chalco by about 1465, gaining the two largest areas of fresh water in the basin, and many historians think the state then organised a large expansion of chinampas. Pedro Armillas mapped the southern chinampa zone from air photographs in 1971 and showed it was far larger than previously thought, and totals of roughly 9,000–12,000 hectares are commonly given. Lee Arco and Elliot Abrams estimate that building the system took about 25 million person-days, each one person’s work for one day, over forty years, a task local communities could manage, though perhaps under state direction. Jeffrey Parsons argued that the chinampas supplied a large share of the city’s food, enough for perhaps 100,000 people or more, though not the whole of it, which is why the city could never stop relying on its empire.
The rest came through exchange and tribute, which tied the city’s diet to its empire. At Tlatelolco, Bernal Díaz recalled, soldiers who had seen Rome and Constantinople said they had never seen a market so large, orderly and crowded. Small purchases were paid in cacao beans and larger ones in cotton cloaks called quachtli, each worth between about 65 and 100 beans. The Codex Mendoza, a painted book recording the tribute owed by each province much like a tax register, shows 42 great bins of grain sent as tribute, but historians debate how large they were and how often they were filled. Population estimates for Tenochtitlan range from under 100,000 to over 300,000, and Michael Smith’s figure of 212,500 on 13.5 square kilometres lies within the common range. A city that size could exist only because lake, market and empire all fed it at once.
WHY IT HAPPENED
Frost and unreliable rain threatened ordinary fields. At over 2,200 metres, rain-fed maize risked early frost in September and depended on summer rains that could fail, as they did in 1452–54. Chinampas avoided both dangers, since water seeped up from below and the lake moderated the night-time cold. The technique was therefore an adaptation to the basin’s particular climate, turning the lake’s shallow margins into the safest farmland available, much as irrigation protects modern farmers against a dry season.
The dike freshened water for new fields. Chinampas need fresh water, because salt kills crops, so they flourished in the spring-fed southern lakes and could spread around Tenochtitlan only after Nezahualcoyotl’s dike separated the western lagoon from salty Lake Texcoco around 1449. On the map, chinampa fields appear in the lagoon south of the city by 1469. Hydraulic engineering and farming innovation reinforced each other, since each made the other more valuable. The chinampa boom of the later fifteenth century was therefore a by-product of flood control.
Conquest gave the state control of the best water. Control of the freshwater lake towns tied farming to conquest. The alliance conquered Xochimilco and the lake towns around 1430 and the Chalco confederation by about 1465, after decades of war. Control of these towns gave the Mexica state access to the largest freshwater farming zones in the basin and the labour of the people who worked them, so that agricultural expansion followed military victory. Imperial power and chinampa farming grew together, each paying for the expansion of the other.
A growing city needed food on a scale no island could supply. Tenochtitlan’s population grew from a few thousand in the 1300s to perhaps 150,000–200,000 or more by 1519, crowded onto about 13.5 square kilometres of island. Even the most intensive farming in the lake could not feed such numbers, so the city drew on markets and tribute from far beyond the basin. Growth itself drove the search for new sources of food, which pulled the empire outward toward the warm, wet lowlands of the Gulf coast.
THE TURN
The conquest of Xochimilco, c. 1430. The alliance’s conquest of Xochimilco and the neighbouring lake towns soon after 1428 is the hinge of this chapter because it put the basin’s most productive farmland under the control of the state that most needed it. Chinampas had been built by local communities for generations, but now a powerful centre could direct labour, expand the fields and take their produce as tribute. That combination of an old technique with new political power created the food supply that allowed Tenochtitlan to grow into one of the largest cities in the world.
WHAT IT CHANGED
One of the world’s largest cities. The food system made possible one of the largest cities on earth, since by 1519 Tenochtitlan and Tlatelolco together probably held 150,000–200,000 people or more, larger than any city in Spain at the time. The scale astonished the Spaniards who arrived in November 1519, and Chapter 10 shows how its planners organised such numbers on an island, with water, streets, canals and waste all managed together as a single system.
A food supply tied to empire. Because the city depended on tribute and trade from distant provinces, any disruption of the empire threatened its food. Provinces that resented tribute could rebel, and enemies could cut supply routes. In 1521 the alliance’s former subjects joined the Spaniards and blockaded the lake, so the dependence that had fed the city became a weapon against it, as Chapter 11 explains.
A technique that outlived the empire. The chinampas of Xochimilco survived the conquest and are still farmed in parts of southern Mexico City today, where they form part of a UNESCO World Heritage site and supply vegetables and flowers. The longevity of the technique contrasts with the fall of the empire that expanded it, a pattern the epilogue explores, in which a farming technique outlasts the state that once commanded it.
DISCUSSION QUESTION
How far did the chinampas, as opposed to tribute and trade, make Tenochtitlan possible?
The chinampas were essential but not sufficient, and the evidence supports a balanced answer. Their high, frost-protected yields, perhaps three times those of rain-fed fields, and the expansion of the southern chinampa zone after the conquests of Xochimilco and Chalco, gave the city a reliable food supply close to home that could be delivered fresh by canoe. Jeffrey Parsons estimated that they could feed perhaps 100,000 people or more. Yet most estimates put the city at 150,000–200,000 or higher, so a large share of its food must have come through the Tlatelolco market and from tribute, including grain bins, beans and cotton from distant provinces. Uncertainty about chinampa area, city size and tribute volumes means that precise shares cannot be calculated. The transferable insight is that great cities rest on several food systems at once, and their resilience depends on how many of those systems can fail before the city goes hungry.
AN INTERESTING FACT
Mexica money could be forged, even though it grew on trees. Cacao beans were used as small change in the markets of the basin, and the Florentine Codex, compiled under the friar Bernardino de Sahagún in the sixteenth century, describes dishonest cacao sellers who removed the contents of the beans and filled the empty shells with earth or other material so that they passed for good money. Counterfeiting coins is usually associated with metal currency, yet the Mexica faced the same problem with beans, which shows that cacao functioned as real money worth cheating with.
CHAPTER 10 · c. 1430–1519 · 1519
The Planned City
The city’s layout expressed a religious idea and solved practical problems at the same time. At its centre stood the sacred precinct, roughly 430–460 metres across, where the friar Bernardino de Sahagún’s informants listed 78 structures, dominated by the Templo Mayor, a pyramid with twin shrines to Huitzilopochtli, god of war and the sun, and Tlaloc, god of rain. Excavations led by Eduardo Matos Moctezuma since 1978 show that the temple was enlarged in seven major building stages. The causeways leading north, west and south divided the island into four quarters, Moyotlan, Teopan, Atzacoalco and Cuepopan, and each was split into neighbourhoods called calpolli, about seventy in all. A calpolli worked much like a modern borough, with its own temple, school and local officials, so the city could be governed in manageable units.
The plan also managed water, which was the city’s greatest risk and resource. On the map, the causeways, raised roads across the lake, radiate from the island, with the dashed blue aqueduct running in from Chapultepec in the west. Canals ran beside many streets, so goods arrived by canoe at house doors and the city drained after rain. The causeways had gaps crossed by wooden bridges, which let water flow between the parts of the lake and could be removed for defence. Fresh water from Chapultepec ran along the Tlacopan causeway and entered the precinct, while canoes carried it to other districts for sale. Bernal Díaz described human waste being sold from canoes for tanning leather and latrines built of reeds along the roads, and much of the city’s waste went to the chinampas, the raised fields in the lake, as fertiliser. The system kept wastewater out of drinking water, so the city stayed healthier than many European towns of the time.
The meeting of 8 November 1519 is the moment when outsiders first described this system, and their accounts are vital but biased evidence. Moctezuma II came out to meet Cortés at Huitzillan, near where the southern causeway entered the city, and the Spaniards marched in along the route traced by the dark arrow. Cortés’s second letter to the emperor Charles V, sent in 1520, describes a city built on a salt lake, reached by causeways, with an aqueduct of two channels and a market where more than 60,000 people traded each day. Díaz, writing decades later, recalled soldiers asking whether what they saw was a dream. Both men wanted to impress Spanish readers with the scale of what they had conquered. Their wonder nonetheless confirms what archaeology shows, that Tenochtitlan was among the largest and best-organised cities in the world.
WHY IT HAPPENED
Life on water demanded planning. A city on islands in a shallow lake could not grow haphazardly, because every new house lot had to be built up from the lake bed and connected to canals for transport and drainage. Expansion meant building chinampas outward from the island’s edge in regular rows. The environment itself pushed the Mexica toward an orderly grid of streets and canals, so planning followed from the decision to build on water.
Hydraulic works made a large city possible. The dike of about 1449 protected the island from floods and freshened the lagoon, and the aqueduct working by 1466 delivered reliable drinking water. Without these works the city could not have grown much beyond the size of its early decades. The planned city of 1519 was therefore built on the engineering of the mid-fifteenth century, which turned a hazardous lake into habitable space for perhaps 200,000 people. Engineering came first, and the planned city followed it.
Tribute paid for monumental building. The temples, palaces and causeways of Tenochtitlan required stone, timber, lime and labour drawn from across the basin and beyond. Tribute from subject provinces supplied many of these materials and fed the workers, and rulers competed to enlarge the Templo Mayor as a display of imperial power. The city’s grandeur was the capital’s share of an empire’s wealth, made visible in stone at the very centre of the lake. Imperial tribute and urban grandeur therefore rose and fell together.
Religion organised space. Mexica religion placed the Templo Mayor at the centre of the cosmos, the point where the earthly world met the heavens and the underworld, and the four quarters reflected the four directions of the universe. Building the city as a cosmic diagram gave rulers legitimacy and gave every resident a place within a sacred order. Religious ideas and practical planning therefore pointed in the same direction, which helps explain why residents maintained the system so carefully.
THE TURN
Huitzillan, 8 November 1519. The meeting of Moctezuma II and Hernán Cortés at the edge of the city on 8 November 1519 is the hinge of this chapter because it is the moment the planned city entered the written record of outsiders, and the moment its future turned. The Spaniards’ astonished descriptions are the main written evidence of what ninety years of Mexica engineering had produced. Within twenty months the same causeways, canals and aqueduct would become the battlefield of a siege. The hinge is therefore double, marking both the high point of the lake city and the arrival of the force that would destroy it.
WHAT IT CHANGED
A city the Spaniards would rebuild on. After the conquest the Spaniards built Mexico City on the ruins of Tenochtitlan, keeping the main causeways as streets and placing the cathedral and viceregal palace on the sacred precinct and Moctezuma’s palace. The old grid survives in the street plan of the modern historic centre, which shows how lasting the Mexica plan has been even after the lake beneath it was drained.
The causeways become battle lines. The causeways that linked the city to the shore and made it accessible also made it vulnerable. During the Spanish retreat of June 1520 and the siege of 1521, the fighting concentrated on the causeways and their bridges, where the gaps that once let water flow became deadly obstacles. Chapter 11 follows how the city’s plan, built for peace, shaped its fall in war.
A model for later comparison. Tenochtitlan’s combination of canals, aqueducts and waste recycling has made it a favourite comparison for modern debates about sustainable cities. Historians caution against romanticising it, since its order rested on tribute and forced labour, but its management of water and waste remains a striking example of an engineered urban environment, and one that was already more than a century old when Europeans first saw it.
DISCUSSION QUESTION
Was Tenochtitlan’s plan primarily a solution to environmental problems or an expression of political and religious power?
The plan was both, and the strongest answers show how the two reinforced each other. Environmental needs shaped the grid of streets and canals, the removable bridges on the causeways, the aqueduct and the recycling of waste, all of which made a dense city on water workable. Political and religious power shaped the sacred precinct at the centre, the alignment of the causeways and quarters with the four directions, and the repeated enlargement of the Templo Mayor, which advertised each ruler’s strength. Even the hydraulic works were political, since only a powerful state could command the labour they required, and the shrine to the rain god Tlaloc on the Templo Mayor placed water at the heart of religion. Historians still debate how far the residential districts were planned from above. The transferable insight is that the most effective environmental technologies are often embedded in political and religious systems that give people reasons to build and maintain them.
AN INTERESTING FACT
The rediscovery of the Templo Mayor began by accident in the early hours of 21 February 1978, when workers from the city’s electricity company, digging a trench at the corner of two streets behind the cathedral of Mexico City, struck a carved stone. It was a great disc of pink andesite, about 3 metres across and weighing roughly 8 tonnes, showing the dismembered moon goddess Coyolxauhqui. Its discovery led the government to demolish a block of colonial-era buildings so that archaeologists led by Eduardo Matos Moctezuma could excavate the temple beneath, which now lies open beside the cathedral.
CHAPTER 11 · 1450s–1521 · 1521
The Flower Wars and the End of the System
The flower wars, ritualised battles fought by agreement to take captives, somewhat like scheduled tournaments with lethal stakes, show how the empire managed enemies it could not, or chose not to, conquer. According to the Texcocan chronicler Fernando de Alva Ixtlilxochitl, the Alliance agreed in 1454, in the last year of the great famine, to fight Tlaxcala, Huexotzinco and Cholula on agreed fields, usually near Atlixco, to take captives for sacrifice while leaving each other’s lands untouched. Diego Durán credits the Mexica adviser Tlacaelel with the idea. Ross Hassig argues that these were deliberate wars of attrition, cheap ways to wear down strong enemies, while Barry Isaac argues that the ritual explanation was invented later to hide a failure to conquer. Meanwhile the Alliance encircled Tlaxcala with tributary provinces, conquered regions that paid regular tribute like a tax, and, according to Tlaxcalan complaints recorded by the Spaniards, cut off its salt and cotton. Exclusion created a neighbour with every reason to seek revenge.
Human sacrifice was central to Mexica religion, which taught that the gods had sacrificed themselves to create the sun and needed human blood to keep the world in motion, and its scale is debated. Chroniclers claimed tens of thousands of victims at the rededication of the Templo Mayor in 1487, with Durán giving 80,400, while an Indigenous pictorial source gives 20,000 and many historians think the larger figures inflated. Excavations of the great skull rack since 2015 have identified 655 skulls, including women and children. Sacrifice mattered politically because many victims were war captives or tribute from subject peoples, which deepened the resentment the empire inspired. When Cortés reached Cempoala in 1519, the Totonac ruler complained of Mexica tribute collectors, and in September Tlaxcala, after fighting the Spaniards, chose to ally with them. The resentment that tribute and sacrifice had built became the raw material of the coalition that destroyed the city.
The conquest combined Indigenous alliances, epidemic disease and the lake itself. At Cholula in October 1519 the Spaniards and their allies killed thousands, Cortés admitting about 3,000, and on 8 November they entered Tenochtitlan. In May 1520 Pedro de Alvarado’s men massacred celebrants at the festival of Toxcatl, and on the night of 30 June the Spaniards fled along the Tlacopan causeway with heavy losses, reaching Tlaxcala after the battle of Otumba. Smallpox, which arrived with Pánfilo de Narváez’s expedition, raged through the city from about October 1520 for sixty days. Cortés returned with thirteen brigantines, small sailing warships built with Tlaxcalan help and used on the lake much like modern patrol boats, tens of thousands of Indigenous allies and under a thousand Spaniards. From late May 1521 the aqueduct was cut and the city blockaded until it fell on 13 August, its people dying of hunger, thirst and disease. The siege worked because the aqueduct, causeways and canoe routes that had fed a city of 200,000 were the very points a besieger could cut.
WHY IT HAPPENED
Tribute and encirclement created enemies. The empire that fed Tenochtitlan rested on tribute from conquered peoples who kept their own rulers and resented the burden, and on the encirclement of independent rivals. Tlaxcala, surrounded by Mexica tributary provinces and reportedly cut off from salt and cotton, nursed long grievances, and Totonac lords complained of tribute collectors. When an outside force appeared, these peoples saw a chance to overturn Mexica rule, and many took it within months.
Unfinished wars left strong rivals. The Alliance never conquered Tlaxcala, Huexotzinco or the Tarascan kingdom, whose army destroyed a Mexica force near Taximaroa around 1478–79, killing, by Durán’s probably inflated count, over 20,000 men. Fortified frontiers faced each other, with the Mexica fortress of Oztuma against Tarascan strongholds. These undefeated neighbours gave any invader potential allies and a secure base, which Tlaxcala provided for Cortés in 1520 when he retreated from the city with his army broken.
A new disease met a population without immunity. Smallpox had never reached the Americas, so nobody had immunity, and it spread rapidly after arriving with Narváez’s expedition in 1520. The Nahua accounts in the Florentine Codex describe victims too covered with sores to move and many who starved because nobody could care for them. The epidemic killed the ruler Cuitlahuac after about eighty days in power and weakened the defenders before the siege, while sparing the Spaniards, most of whom had survived childhood exposure.
The engineered lake had points of failure. Tenochtitlan depended on causeways for land access, an aqueduct for drinking water and canoes for food, all of which could be cut. The dike that had freshened the lagoon became an obstacle that Spanish brigantines, small sailing warships built on the lakeshore, broke through, and the aqueduct from Chapultepec was severed at the start of the siege. The very works that had made the city great gave a besieger clear targets, and the Spaniards’ allies knew exactly where they were.
THE TURN
Tlaxcala chooses alliance, September 1519. The decision of Tlaxcala’s rulers to ally with Cortés in September 1519, after defeating and then negotiating with his small force, is the hinge of this chapter. Without Tlaxcala the Spaniards would have had no secure base, no army of tens of thousands and no refuge after their flight from Tenochtitlan in 1520. The choice was made by an independent state pursuing its own long war against the Triple Alliance. It shows that the fall of the Mexica system came from within Mesoamerica’s own politics as much as from outside.
WHAT IT CHANGED
The fall of Tenochtitlan. The city fell on 13 August 1521 when Cuauhtemoc, the last ruler, was captured on the lake. Tens of thousands of people had died of hunger, thirst, disease and violence, and the chroniclers’ figures of up to 240,000 cannot be checked. A plaque set up at Tlatelolco in the 1960s reads, in translation, “It was neither triumph nor defeat; it was the painful birth of the mestizo people that is the Mexico of today.”
A population catastrophe. Smallpox in 1520 was followed by further epidemics, including the cocoliztli of 1545, which struck during a severe drought recorded in tree rings. Central Mexico’s population fell by perhaps 80–90 percent within a century, from an uncertain starting point of perhaps 5–25 million to about 1 million. The labour that had maintained the lake system, its dikes, canals and fields, largely disappeared.
Spain inherits the lake. The Spaniards rebuilt the city on the ruins and inherited its hydraulic problems without the Mexica knowledge or labour that had managed them. Floods in the following century led them to begin draining the lake, a choice whose consequences, from the great flood of 1629 to the sinking of Mexico City today, the epilogue examines. The skills and labour that had kept the lake in balance were lost within a generation.
DISCUSSION QUESTION
Why did the Mexica system, so effective against the environment, prove so vulnerable to its human enemies?
The Mexica system was built to manage water, frost and food, and the same features that made it effective against nature made it exposed to a coordinated human attack. Concentrating perhaps 200,000 people on an island made the city efficient to feed by canoe and causeway, but it also meant that cutting the aqueduct, controlling the lake with brigantines and blocking the causeways could starve it. The tribute empire that supplied food also produced resentment among subject and encircled peoples, who provided the tens of thousands of allies without whom the Spaniards could not have won. Smallpox, a shock no Mesoamerican society could have anticipated, removed leaders and defenders at the decisive moment. Historians differ on the weight of each factor, with Restall and Townsend stressing Indigenous politics and others stressing disease and Spanish technology. The transferable insight is that systems optimised for one kind of threat can concentrate vulnerability to another.
AN INTERESTING FACT
The most detailed Indigenous picture of the conquest was painted to win privileges from the Spanish crown. Around the 1550s the town council of Tlaxcala commissioned the Lienzo de Tlaxcala, a great painted cloth showing scene after scene of Tlaxcalan warriors fighting beside the Spaniards, from the first alliance to the siege of Tenochtitlan and later campaigns. Its purpose was to prove Tlaxcala’s loyalty and earn exemptions from tribute. The original cloth has been lost, and historians study it through later copies, including one made in 1773, as a Tlaxcalan account in which the Tlaxcalans are the heroes.
EPILOGUE · c. 1450–1521 AND AFTER · 1500
Two Answers to the Environment
The inquiry question, how societies innovate to live with a demanding climate, shows that climate mattered in both cases, but in different ways. For the Norse, climate set the stage, since the warmth of about 950–1250 made Greenland’s fjords farmable and the cooling and drying after about 1275–1300 narrowed the margin again. For the Mexica, climate brought sudden shocks inside a stable pattern: the floods of 1449 and 1499, the frosts and drought of 1450–54 confirmed by tree rings, and a long drought from 1514 to 1539 that overlapped the conquest. The Norse met slow change with gradual adaptation, eating seals and shifting trade, until leaving made more sense. The Mexica met sudden shocks with engineering, storage and conquest of warmer lands. Each society answered the climate it actually faced.
The difference in scale explains much of the difference in outcome. Norse Greenland held perhaps 2,000–2,500 people, about as many people as one of Tenochtitlan’s seventy neighbourhoods, while the Basin of Mexico held perhaps 1–1.5 million. Small numbers made the Norse colony easy to found and impossible to defend against compounding pressures, since every lost ship, failed hay harvest or slump in ivory prices hit a society with no reserves. Large numbers let the Mexica build dikes and chinampas, raised fields built up from the lake bed like garden beds standing in water, and absorb a famine, but they also tied the city to tribute that made enemies and to structures that a besieger could cut. The cost chart below shows the scale of each society. The Norse failed through smallness and the Mexica fell through concentration, which are opposite versions of the same weakness, a lack of spread risk.
The legacies of the two cases show which kinds of innovation lasted and which did not. In Greenland the Inuit, whose boats, harpoons and lamps suited the sea ice, became the island’s people, and the Norse ruins at Hvalsey and elsewhere are now a UNESCO World Heritage site. Iceland survived with its law and literature. In Mexico the Spaniards kept the city and abandoned the Mexica way of living with the lake, digging a drainage tunnel at Huehuetoca in 1607–08. In 1629, with the tunnel closed for repairs, heavy rains left the city under water for about five years, and the response was to drain ever more of the lake for three centuries. Today parts of Mexico City, built on dried lake clay, sink by up to about 50 centimetres a year, while the chinampas of Xochimilco are still farmed. Innovations survived when they worked with the environment’s variety, and failed when they bet everything on a single resource or a single place.
WHY IT HAPPENED
Different environments demanded different answers. The North Atlantic offered scattered pockets of grass and rich seas separated by dangerous water, which rewarded mobility, ships and trade. The Basin of Mexico offered a concentrated, fertile lake system in a closed valley, which rewarded engineering and the organisation of labour. Each society’s innovations fitted the opportunities its environment offered, which is why their systems look so different despite facing the same underlying problem of a demanding climate.
Scale shaped resilience. The Norse colony in Greenland held a few thousand people at most, while the Basin of Mexico held more than a million, a difference of several hundred times. Scale decided how much labour could be mobilised, how much food could be stored and how many losses could be absorbed. It explains why the Mexica could build dikes and survive famine and why the Norse colony had so little margin when its pressures combined.
Single points of failure decided both endings. Norse Greenland depended on one export, walrus ivory, and one link to Europe, the ships from Bergen, so their decline left the colony with no fallback. Tenochtitlan depended on causeways, an aqueduct and canoe supply across one lake, which a besieger could cut. In both cases the end came where the system concentrated its dependence, which is the strongest common lesson of the comparison and the hardest to see while a system is succeeding.
Other peoples with different systems replaced both. In Greenland the Thule Inuit, with technology built for sea ice, expanded as the Norse withdrew, and in Mexico Spanish colonists, with their own diseases, livestock and engineering, replaced the Mexica state. In both cases a different system took over the same environment, one adapting to it and one attempting to remake it, which shows that an environment sets the price of each way of life and leaves the choice to the people living in it.
THE TURN
Hvalsey and Tenochtitlan: two kinds of ending. The silent ruin of Hvalsey church and the drained lake beneath Mexico City are the two endpoints of this atlas, and placing them side by side is the hinge of the comparison. Norse Greenland ended in a quiet withdrawal, with a church left standing and farms abandoned in order, because a small society concluded that the costs of staying outweighed the gains. Tenochtitlan ended in a siege, and its lake system was then dismantled by new rulers with other priorities. One system faded through smallness and distance; the other was broken through its concentration and remade by conquerors.
WHAT IT CHANGED
Greenland becomes an Inuit land, then a Danish colony. Inuit communities spread along Greenland’s west and south coasts by about 1500. Danish colonisation began in the eighteenth century and shaped the island for two hundred years. Greenland’s colonial status ended in 1953, Home Rule followed in 1979 and Self-Government in 2009. The Norse ruins became a focus of national and scholarly memory, and in 2017 the farming landscape of Kujataa, including Hvalsey, joined the World Heritage list.
The lake becomes a sinking city. Mexico City grew on the bed of the drained lake into one of the world’s largest cities, and it still faces both flooding and subsidence, sinking by up to about 50 centimetres a year where the compressible lake clay is thickest, as groundwater is pumped from beneath it. The Mexica problem of living with water in a closed basin remains the city’s central environmental challenge five centuries later.
A question for the present. The inquiry this atlas has followed, how societies innovate to live with a demanding climate and why some innovations last, has become a question for every society facing climate change. The two cases suggest that lasting adaptation depends on spreading risk across resources, places and people, and on institutions able to change as conditions change, which is a historical argument that students can test against the sources in this atlas.
DISCUSSION QUESTION
Which society’s response to its environment was more successful, and by what standard should success be judged?
The answer depends on the standard chosen, and stating that standard explicitly is the key to a strong answer. Judged by scale and achievement, the Mexica were far more successful, since their dikes, aqueducts, chinampas and tribute fed a city of perhaps 200,000 and survived famine and flood, while Norse Greenland never exceeded a few thousand people and was abandoned. Judged by longevity, Norse Greenland lasted about 450 years, longer than the Mexica empire’s century of dominance after 1428, and Iceland endures today. Judged by the survival of innovations, both left lasting techniques, the clinker ship, the stockfish trade and the Althing from the Norse, and the chinampas from the Mexica. Neither society was undone by climate alone, since the Norse faced compounding economic pressures and the Mexica a coalition of enemies and an epidemic. The transferable insight is that success in adapting to the environment must be measured over time and against all the shocks a society faces, human as well as natural.
AN INTERESTING FACT
Europeans rediscovered Greenland while looking for people who were no longer there. In 1721 the Norwegian priest Hans Egede sailed from Bergen to Greenland, hoping to find descendants of the medieval Norse settlers and bring them into the Lutheran church, since nobody in Scandinavia knew whether they had survived. He found only Inuit, learned their language and stayed to work among them. His first mission stood on a small island, and in 1728 the colony moved to the mainland under the governor Claus Paarss as Godthåb, today’s Nuuk, the capital of Greenland. A mission to the vanished Norse became the beginning of Danish rule over the Inuit who had replaced them.