Climate and Innovation: The Norse and the Aztecs, c. 790–1521 — the study guide

CHAPTER 1 · c. 950–1450 · 1250

Climate as a Force in History

A warm period in one place need not be warm everywhere. Michael Mann and colleagues compared hundreds of records in 2009 and found that, between 950 and 1250, the North Atlantic was relatively warm while parts of the tropical Pacific were cool. The name Medieval Climate Anomaly describes such a regional departure from the usual pattern, rather as an unusually hot decade might stand out in a city's records.

Even Greenland offers different histories. Remains of midges in southern Scoop Lake suggest summers about 1.5 °C warmer in 900–1400 than in the colder centuries on either side. Farther north and inland, lakes near Kangerlussuaq record a drop of about 4 °C in roughly eighty years from around 1100. Gifford Miller's team dates the onset of a later cold period to 1275–1300: volcanic eruptions put sulphur into the atmosphere and dimmed sunlight, the team argues, while expanding sea ice prolonged the cooling. A record from one location cannot simply tell us what a neighboring community experienced.

How do we know about temperatures before thermometers? Scientists use proxies, natural records that preserve signs of past conditions. At Summit, the highest point of the Greenland ice sheet, the American GISP2 team drilled 3,053 metres to bedrock in 1989–93; the European GRIP core reached 3,028 metres in 1992. Snow from successive years remains in layers, and the proportion of a heavier form of oxygen varies with temperature. The ice thus preserves evidence from which past temperatures can be reconstructed.

Other records answer different questions. Lake muds provide evidence of rainfall, and tree rings can fix events to particular years. A burst of cosmic radiation left a signal in the ring for 993 that helped date Norse timber in Newfoundland. People left records too: Icelandic annals describe ice and hard winters, and Mexica chronicles report frosts and droughts in the 1450s that Mexican tree rings also support. Ice, wood and writing came into being in different ways; agreement among them gives an explanation firmer ground.

The comparison in this atlas begins with two different ways of making a home. The Norse, Scandinavian peoples of the Viking Age, settled Iceland in the 870s and Greenland in the 980s, reaching North America around 1000. Their history asks whether farming near its climatic limit could endure later change. The Mexica remained in one basin, using dikes, aqueducts and raised fields to manage a lake threatened by salt, flooding and frost. In each case inventions worked within a larger society: its population, food supply and trade shaped how much protection those inventions could provide.

WHY IT HAPPENED

Living at the margin magnifies small changes. Hay linked Greenland's short summer to the survival of cattle through eight winter months. Too little warmth or moisture could leave the animals without enough feed. Mexica maize faced a different limit at about 2,240 metres: an early autumn frost could kill the crop before it ripened. Near such limits a shift of a degree or two could turn an ordinary harvest into a desperate year.

Ocean currents and sea ice shape the routes. Ships connected Greenland to Norway, but the sea also carried an obstacle. The cold East Greenland Current, shown by the grey arrow, moves Arctic ice down the east coast and around Cape Farewell. As cooling made drift ice more extensive and longer-lasting in summer, harbors could be blocked and voyages stretched out. The connection became slower and riskier just as the settlements depended on it.

Volcanoes can tip a climate into a new state. Sulphur from a large eruption can reach high into the atmosphere, reflect sunlight and cool the world for several years. Gifford Miller's team argued in 2012 that four large eruptions over roughly fifty years helped initiate the Little Ice Age in 1275–1300; the sequence included the 1257–58 eruption later traced to Samalas in Indonesia. Expanding sea ice could then reflect more sunlight, keeping summers cold after the volcanic haze had cleared.

Societies build their own vulnerabilities. A settlement of perhaps 2,000–2,500 people in Norse Greenland had a small margin against repeated bad years. Tenochtitlan, perhaps 200,000 strong, could draw on an empire for food, but placed a large population on one lake. Population, food diversity and trade determined what resources each society had when cold or drought struck. A shock that one community survived could be fatal to another.

WHAT IT CHANGED

The warm centuries open the sea road. Norse voyages to Iceland, Greenland and North America coincided with the relatively warm centuries of roughly 950–1250. Climate helped set the conditions for open-ocean crossings; ships and the farming society that supported them made the voyages possible. Chapter 2 takes up that combination.

The cold tests the farms. Greenland's outlying farms depended on hay and cattle, while walrus ivory supported trade. Cooling after about 1275–1300 placed those arrangements under pressure. Chapter 5 weighs that pressure with markets, isolation and choice in asking why the Norse left while newly arrived Inuit stayed and prospered.

A second laboratory in Mexico. The Basin of Mexico faced floods in 1449 and 1499 and frost and drought in the 1450s. Chapter 8 examines dikes, aqueducts and granaries as Mexica responses. By supporting a larger population on the lake, those measures also meant that a later failure could harm more people.

DISCUSSION QUESTION

Can climate ever be the cause of a society’s success or failure, or only its context?

Climate can cause a change without explaining the outcome by itself. Warmer centuries widened the opportunity for farming in Norse Greenland; cooling after 1275–1300 narrowed it. Yet Iceland endured the colder period, and Thule Inuit expanded into Greenland while the Norse withdrew. Different food and tools made survival possible under cold conditions. Even the evidence of physical change differs by location: Lake 578 records drying near a farm, while the summit cores record conditions high above the settlements. Historians study vulnerability by asking how population, trade, technology and choices exposed people to a pressure or helped them withstand it. The same shock could be an inconvenience to one society and a catastrophe to another.

AN INTERESTING FACT

A beer bottle helped give scientists a way to read ancient temperatures in ice. On a rainy Saturday at the end of June 1952, Danish physicist Willi Dansgaard set an empty bottle and funnel in his garden at Herlev, near Copenhagen, and collected successive showers. The proportion of heavy oxygen in the rain varied with the temperature of the cloud from which it fell. Dansgaard reasoned that, if snow retained the same signature, Greenland's ice sheet could preserve a temperature record. Two decades later he read that record alongside the history of the Greenland Norse.

CHAPTER 2 · c. 790–900 · 866

The Ship and the Sea Road

A ship able to cross open water and land without a deep harbor gave its crew choices that defenders could not easily anticipate. Scandinavian ships had a keel to help hold course under sail, and overlapping planks that flexed with the waves. Their shallow draft—the depth of hull below the waterline—let them approach shore. A fleet could choose a landing place and arrive before a defending army had gathered.

Buried ships and vessels sunk as barriers show how this was done. Oseberg, built around 820 and buried in 834, measured 21.5 metres and had fifteen pairs of oars. Gokstad, built from timber felled around 890, had thirty-two oar positions and a draft of about a metre, roughly an adult's waist height. A later warship, Skuldelev 2, was built near Dublin around 1042. At 30 metres long, it could carry some 65–70 people. These vessels differed in size, but their ability to combine sea passage with access to shore helped make the ship an instrument of power.

The ship's materials lead us back to the farms. Oak grew in forests that took a century to mature; iron for rivets came from bog ore smelted in charcoal furnaces. The sail demanded a still more visible investment of labor. Lise Bender Jørgensen calculates that a cargo sail needed well over 200 kilograms of wool and about ten years of work. A warship's sail required more than 1.5 tonnes and fifty to sixty years of labor, almost all performed by women. Chieftains able to draw on many farms could gather the resources embodied in a fleet.

A seaworthy ship made travel possible; it did not by itself give a crew a reason to leave. James Barrett argues that young unmarried men sought wealth, including payment due to a bride's family. Ben Raffield, Neil Price and Mark Collard connect such pressure to polygyny, in which some powerful men had several wives. The search for wealth could take men to market as well as to a raid. Hundreds of thousands of Islamic silver coins, known as dirhams, have been found in Scandinavia, and Kaupang and Hedeby were thriving trading towns.

The attack on Lindisfarne in 793 brought the danger of the sea home to its victims: monks were killed or carried off, and Alcuin wrote from Charlemagne's court of the shock of such a voyage. Other records show the commercial reach of the same world. Around 890 the Norwegian chieftain Ohthere told King Alfred of Wessex that he hunted walrus for tusks and hides and collected fur tribute from the Sámi, the herding and hunting people of the far north. Dublin became a Norse town from 841, and a great army took York in 866. Routes used for exchange and attack also became routes to places where Scandinavians settled and ruled.

WHY IT HAPPENED

A scarcity of farmland at home. Norway's mountains, forests and rock left only about 3 percent of its land available for cultivation. Good farms along the fjords were limited and passed to eldest sons. Younger sons and landless men had reason to seek wealth elsewhere. Ships could take them abroad to trade or raid, and later carry families west to clear and defend land for farms.

Silver from the Islamic world. Silver minted by the Abbasid caliphate and its neighbors traveled north in the ninth and tenth centuries, through Russian rivers and across the Baltic, in exchange for furs and enslaved people. Scandinavian finds include hundreds of thousands of these dirhams. Silver enriched towns such as Hedeby and enabled chieftains to reward followers; places where wealth accumulated could also attract raiders.

Unguarded wealth across the North Sea. Coastal monasteries in Britain and Ireland held gold, silver and books, sometimes on islands chosen for solitude. They were exposed to crews arriving by sea. Political divisions offered other opportunities: Northumbria had civil wars, and the Frankish empire of Charlemagne's heirs split after 840. A ship gave its crew the mobility to strike a weak point and leave before an army could gather.

A society organised for voyages. A voyage depended on ties established at home. Chieftains drew followers through gifts and oaths, farms supplied wool, and women did much of the spinning and weaving needed for sails. Crews also needed iron and timber, while assemblies helped settle disputes that might keep men at home. These resources and institutions made it possible to send people abroad in the hope of returning richer.

WHAT IT CHANGED

Settlement follows the raiders west. Routes first used by raiders could also bring families looking for farms. Norse settlers took the Northern Isles, Hebrides and Faroe Islands in the ninth century. In the 870s they crossed about 500 kilometres of open sea to Iceland, a volcanic island without a king or native people. Chapter 3 follows the society they established, including enslaved people brought from Gaelic lands.

Norse towns and kingdoms in Britain and Ireland. Some raiders acquired territory and governed it. Dublin became a Norse trading town from 841; after 866 York became the capital of a Norse kingdom. In the 870s and 880s the Danelaw placed eastern England under Scandinavian law. Markets and churches in these centers connected the Norse world to western Europe and later colonies depended on those connections.

Walrus ivory enters the story. In the 890s Ohthere described a trade in walrus tusks and hide ropes from the far north to southern markets. Greenland's Norse later hunted walrus far up the west coast, and ivory became an economic engine for their colony. Chapter 4 follows the trade and the dependence that could grow around a single export.

DISCUSSION QUESTION

Was the Viking expansion driven more by the ship or by the society that built it?

Both belong in the explanation. Without a seaworthy, shallow-drafted ship, ambition could not have carried crews to Lindisfarne, Dublin or Iceland. Yet similar vessels existed in Scandinavia for a century before 793. Why were they then used for expansion? Historians point to scarce land, young men's need for marriage wealth, competition among chieftains and incoming Islamic silver, while disagreeing about their relative importance. Written accounts often come from victims and say little directly about Scandinavian motives. The ship itself also depended on social organization: Lise Bender Jørgensen's estimate of decades of women's labor for a warship sail shows what farming communities had to supply. A motive to sail and the capacity to equip a voyage worked together.

AN INTERESTING FACT

In 834 the Oseberg ship was hauled ashore beside the Oslo fjord and buried beneath a turf mound with two women, one probably in her seventies or eighties and the other about fifty. A carved wagon, three sledges, beds, tapestries and kitchen tools accompanied them, along with the bodies of horses and oxen. Clay helped seal air out of the mound, preserving the ship until excavation in 1904. The grandest Viking ship burial yet found shows the extraordinary honor that could be given to women in Viking-age society.

CHAPTER 3 · 870–1000 · 930

Iceland: A Society on a Volcanic Island

The names in Landnámabók, the Book of Settlements, give the migration a scale: nearly 400 leading settlers and about 1,400 places. Population geneticists estimate that 8,000–16,000 people came altogether. Yet the named leaders tell only part of the story. DNA from early settlers’ skeletons led Sunna Ebenesersdóttir’s team in 2018 to estimate their average ancestry at about 57 percent Norse, with most of the rest Gaelic; earlier work found that more than 60 percent of founding female lineages came from Ireland and Scotland. Many Gaelic women and men had been captured in raids and brought as slaves. Their labor helped establish farms in a society whose literary history gives Norwegian leaders greater prominence.

Those farms required supplies for a long winter. Farmers cut hay in summer and stored it for as much as seven months; barley could grow only in the milder south and west. At settlement birch may have covered a quarter to two-fifths of the island. Trees furnished fuel and building material, but sheep ate the young birch that might have replaced them. By the twentieth century woodland covered less than 1 percent. Without its cover, light volcanic soil was exposed to wind and water; perhaps 20,000 square kilometers of soil cover have eroded since settlement. The damage accumulated, while eruptions could change a district suddenly: around 1104 Hekla buried Þjórsárdalur in pumice.

The Althing addressed a problem the land could not solve: how could armed farmers settle disputes without a king? Chieftains, or goðar, combined the roles of local lords and representatives, somewhat like modern political party leaders. They and their followers gathered at Þingvellir for about two weeks each June. There were 36 chieftaincies at first; a reform around 965 made them 39 and established courts for the four quarters of Iceland. Around 1005 a Fifth Court was added to hear appeals. An elected lawspeaker recited a third of the law each summer until it was written down in 1117–18. Judgment and enforcement remained separate: a successful litigant had to carry out the decision. Even so, the system lasted more than three centuries before civil war and submission to Norway in 1262–64.

WHY IT HAPPENED

An empty island within reach of the ships. The crossing was within reach of the ships described in Chapter 2: Iceland is about 970 kilometers west of Norway and about 450 from the already-settled Faroe Islands. Irish hermits may have visited before the Norse, but there was no settled population to conquer. Newcomers could claim land and build a colony from the ground up.

Land hunger and politics in Norway. Later Icelandic writers explained the migration as flight from Harald Fairhair’s tyranny after he united much of Norway in the late ninth century. Historians approach that flattering account of the settlers’ ancestors cautiously. Scarce farmland and growing royal power nevertheless seem to have encouraged ambitious families to leave. In Iceland a chieftain could hold land without a king above him; early claimants took large estates and divided them among kin and followers.

Captives from the Gaelic west. Raids in Ireland and Scotland supplied captives whom settlers took to Iceland as slaves. They cleared land, herded animals and wove cloth. Genetic evidence shows the size of the Gaelic contribution to the founding population. Without forced labor, clearing the island’s usable land in about sixty years would have been much slower. Violence in the Gaelic west helped make the new farms possible.

The need for law without a king. Freedom from royal power left settlers with disputes over land, livestock and killings, and feuds could destroy families. Norwegian regional assemblies, called things, offered a means of resolving such quarrels. Icelanders adapted the tradition to an island-wide assembly, giving people a common procedure without placing one chieftain in command of the others.

WHAT IT CHANGED

A springboard further west. Iceland became a base for the next westward voyages. Erik the Red had been outlawed for killings first in Norway and then in Iceland. He sailed west in the early 980s and returned with plans for a colony; in 985 or 986 a fleet left Iceland for Greenland, as Chapter 4 follows. People who had lost their place in an earlier settlement helped carry the frontier farther west.

A durable legal culture. Iceland lost independence when its chieftains accepted the Norwegian crown in 1262–64, but its legal tradition endured. Law first recited and later written in the Grágás codes remained part of Icelandic identity. The Althing met almost every summer until 1798 and was revived in the nineteenth century; Icelanders count it among the world’s oldest parliaments.

An environment slowly degraded. Fewer trees meant less timber for houses and ships, so Icelanders turned to driftwood and imports. Erosion reduced grazing land as cooling after 1300 brought further pressure. Iceland survived, unlike Norse Greenland, but grew poorer and more dependent on trade with Norway. Chapter 5 follows the colder centuries.

DISCUSSION QUESTION

Was the Althing a successful innovation if Iceland still fell into civil war and lost its independence in 1262–64?

For more than 300 years the Althing helped armed chieftains make law and settle disputes without a king, army or taxes. The peaceful adoption of Christianity in 999 or 1000 shows how much an agreed procedure could accomplish. Yet a judgment depended on the winner’s followers for enforcement. When wealth and power accumulated in a few great families in the thirteenth century, that dependence became dangerous: rivals fought the civil wars of the Sturlung Age and accepted the Norwegian king. The institution had worked under a rough balance of power and struggled when that balance changed, a problem no medieval assembly had fully solved. It nevertheless survived as a symbol and later as a parliament.

AN INTERESTING FACT

The Arctic fox was Iceland’s only native land mammal when the settlers arrived, probably having crossed sea ice at the end of the last Ice Age. Norse ships brought sheep, cattle, horses, goats, pigs, dogs and cats; mice came as stowaways. Icelandic plants had not previously been grazed by anything larger than a goose. The arrival of livestock helps explain the pressure on birch woodland and thin volcanic soils.

CHAPTER 4 · 985–1050 · 1021

Greenland and Vinland

To keep cattle in Greenland, a farmer first needed enough grass to get them through winter. Animals spent about eight months in byres, stone-and-turf sheds, eating stored fodder; the hay harvest therefore limited the herd and a farm’s wealth. Settlers chose the inner fjords, where summers were warmer and grass grew better than on the foggy outer coast. They built about 500 farms in the Eastern Settlement and perhaps 75–100 in the Western. Erik’s Brattahlíð occupied fine land at the head of a fjord, putting some of the best meadows in the hands of the leading household. At its peak around 1200 the colony probably had 2,000–2,500 inhabitants, although older estimates reached 5,000.

Hay supported the livestock, but it could not provide the iron, timber, grain and church goods Greenlanders imported. Walrus hunting supplied something to exchange for them. Each summer men rowed and sailed roughly 800 kilometers north to Norðrseta around Disko Bay, returning with tusks, hides for rope and sometimes polar-bear skins. Ancient DNA studied by Bastiaan Star and James Barrett indicates that by the twelfth century almost all walrus ivory reaching Europe came from Greenland. European craftspeople made chess pieces, crosses and book covers from it. The colony had a place in a luxury market far beyond its fjords, and its prosperity partly rested on the demand of distant buyers.

The voyages west carried Greenlanders farther still. The sagas describe Leif Eriksson finding grass, salmon and mild winters; later expeditions traded and fought with people they called Skrælings, a dismissive Norse term for Indigenous inhabitants, probably ancestors of the Innu or Beothuk of Labrador and Newfoundland. In 1960 Helge and Anne Stine Ingstad found L’Anse aux Meadows, with eight buildings that could have held perhaps 70–90 people. Butternuts found there grow no closer than New Brunswick, evidence that the Norse traveled at least into the Gulf of St Lawrence.

The date of one visit comes from the wood itself. In 2021 Margot Kuitems and colleagues identified a cosmic-radiation signal from 993 in three metal-cut pieces and counted 29 rings from that signal to the bark. The trees were felled in 1021. This fixes a year of Norse activity, though not the first arrival. The base lasted only a few years: Greenlanders could reach America, but keeping a community there posed a different problem.

WHY IT HAPPENED

Warm summers greened the southern fjords. Hay depended on the summer growing season. Midge remains from Scoop Lake near the Eastern Settlement indicate that summers during the Medieval Climate Anomaly, approximately 900–1400, were about 1.5 °C warmer than in colder centuries before and after. In sheltered fjords grass could grow for the hay cattle needed through winter. Erik could see the grass, even if he could not describe the climatic window in modern terms.

Iceland was already full and divided. By the 980s Iceland’s best land had been claimed for two or three generations, leaving younger sons and newcomers fewer opportunities. Feuds could also drive people away: Erik was outlawed for killings in Norway and Iceland. Greenland offered grassland and another start. Perhaps several hundred settlers and their animals embarked in 25 ships in 985 or 986; 14 ships arrived.

A name chosen to attract settlers. A colony needed families willing to make the journey. According to Erik the Red’s Saga, Erik called the land Greenland because an attractive name would encourage people to go, rather as a developer might promote a new town. He kept choice meadows at Brattahlíð for his own farm. The saga’s account was written down more than two centuries later.

European demand for walrus ivory. European craftspeople valued walrus ivory for religious objects and games, particularly when African elephant ivory was scarce. The tusks Greenlanders obtained at Norðrseta could be exchanged for goods their farms could not produce. Ancient DNA indicates that by the twelfth century Greenland supplied almost all the walrus ivory reaching Europe. Demand abroad gave the colony an income beyond subsistence.

WHAT IT CHANGED

A colony locked into hay and ivory. After Vinland, Greenlanders continued to raise cattle and sheep on fjord meadows, eat seals and caribou, and hunt northern walrus for export. This combination worked for about three centuries, but it relied on hay and European demand for ivory. Chapter 5 follows the environmental and economic pressures affecting both after 1250.

Timber trips to Markland continue. The end of the Vinland base did not end voyages to North America. An Icelandic annal records a Greenland ship with 17 or 18 men that had visited Markland and was driven by storms to Iceland in 1347. Markland is generally associated with forested Labrador, a possible source of timber scarce in Greenland. This voyage shows continued contact more than three centuries after the L’Anse aux Meadows timber was cut, though a timber trip was different from a permanent settlement.

Greenland enters the Church and the crown. A bishop took office at Garðar in 1126, and Greenlanders built about fourteen to seventeen churches. In 1261 the colony accepted the Norwegian king’s authority. Connections to Church and crown brought priests, ships and goods, but also made Greenland dependent on decisions in Bergen and Trondheim. Chapter 6 examines those ties.

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 the resources of the society than to a failure of its ships. Norse crews crossed to Newfoundland, repaired vessels and built accommodation for perhaps 70–90 people at L’Anse aux Meadows. Keeping a distant colony supplied and defended was another undertaking. Greenland may have had only 2,000–2,500 inhabitants, and a long voyage separated it from the base. The sagas describe conflict with Indigenous people who were numerous, organized and fighting on their own ground; Norse weapons gave no decisive advantage. Distance made reinforcement and supply harder, while a larger population might have absorbed losses and long voyages more readily. Historians weigh conflict and logistics differently, and the evidence cannot establish that numbers alone decided the outcome. The ships carried this society farther than its resources could readily sustain a community.

AN INTERESTING FACT

The Saga of the Greenlanders presents Snorri, born in Vinland around 1010 to Gudrid Thorbjarnardóttir and Thorfinn Karlsefni, as the first child of European parents born in the Americas. His family returned to farm in northern Iceland. The saga says Gudrid was later widowed, traveled on pilgrimage to Rome and became a nun; it counts several Icelandic bishops among her descendants. In the saga tradition her journeys took her through Iceland, Greenland, Vinland, Norway and Rome, making her one of her century’s most widely traveled people.

CHAPTER 5 · 1250–1450 · 1408

Living with the Cold

A change in diet gives us a way to see the Norse response to cold. Isotopes are chemical signatures in bone that indicate whether a person’s dietary protein came from land or sea. Jette Arneborg’s team estimated that marine food supplied about 20 percent at settlement and about 80 percent near the end. A later study of 123 skeletons placed the early share between 15 and 50 percent and found that it passed 50 percent in the late thirteenth century.

Farm rubbish heaps make the change tangible. Seal bones account for 30 to over 80 percent of the animal remains, chiefly harp and hooded seals taken in communal hunts during their spring migration. Such hunts required organization, and the food they provided became central to the colony. The Norse were adjusting their way of life, not simply refusing to eat what the sea offered.

Keeping farms going remained difficult. Lake 578 near Brattahlíð records a drying trend that would have reduced the hay crop. If several poor summers followed one another, farmers had to slaughter animals they could not feed through winter; the herds then took time to rebuild. Meanwhile the goods that paid for imports were becoming harder to obtain. James Barrett’s study of walrus skulls found smaller animals, often females, taken from farther north, suggesting that nearer herds had been depleted.

The buyers and ships on which Greenland depended were changing too. Europeans were again obtaining elephant ivory, and the Black Death reached Norway in 1349, killing perhaps half or more of its people and shrinking the market. The royal ship serving Greenland sank in 1369 and was not replaced. A colony facing pressure on its farms thus had fewer resources and weaker connections with which to meet it.

The Thule Inuit arrived with equipment for a different use of the same environment. Moving east across Arctic Canada, they reached Smith Sound and Greenland’s far north in the thirteenth century, Disko Bay by the fourteenth, and the south later that century. A toggling harpoon head turned sideways inside a seal, allowing hunters to catch seals at breathing holes in winter ice, a technique the Norse never mastered. Contact could be violent: an Icelandic annal entry for 1379 says that Skrælings, the Norse name for Inuit, killed eighteen Greenlanders and enslaved two boys. The entry survives only in later copies.

The Western Settlement was found empty around 1360. In the Eastern Settlement the last written record is a wedding at Hvalsey in 1408; archaeology carries the account farther. Radiocarbon dating measures the decay of carbon in once-living material, and dates grave clothes to about 1430. By the late 1400s the Norse were gone, while the Inuit remained. Their knowledge and equipment allowed them to make a living from sea and ice through the colder centuries.

WHY IT HAPPENED

Cooler and drier summers cut the hay. Gifford Miller’s team dates the abrupt beginning of the Little Ice Age to about 1275–1300 and another intensification to 1430–1455. At Lake 578 in south Greenland, the clearer signal is drying rather than cooling. This mattered to farmers because cattle needed stored hay for eight months. Several bad summers could force a cull; rebuilding the herd would take years, leaving less in reserve when the next poor harvest came.

Drift ice lengthened and endangered voyages. A voyage from Iceland or Norway became longer and more dangerous as summer drift ice spread along eastern and southern Greenland. A late-medieval sailing guide says the old route was abandoned because of ice, although that sentence may be a later addition. With fewer ships came less iron, timber and grain, less news, and fewer opportunities for people to leave or new settlers to arrive. The colony had less contact through which to address its other problems.

The ivory economy weakened. Greenland used walrus ivory to pay for imports. The trade could still be valuable: about 520 tusks sent as church dues in 1327 were worth roughly 780 cows. But hunters later sought smaller animals farther away, and European buyers were again obtaining elephant ivory from Africa. Greenland was relying on a product that was becoming harder to secure while its market was changing.

Plague and isolation in Norway. Norway’s own crisis weakened its connection with Greenland. The Black Death arrived in 1349 and killed perhaps half or more of the population, reducing the market and shipping. Bergen merchants turned to the profitable dried-cod trade; after the royal Greenland ship sank in 1369, it was not replaced. Thinner contact made iron and timber harder to obtain, and worn iron tools could not be replaced without trade.

WHAT IT CHANGED

Greenland becomes Inuit land. By about 1500 Inuit communities occupied much of Greenland’s west and south coasts, including the former Norse districts. The map’s blue zones trace their movement south. Their descendants make up most of Greenland’s population today. The Norse settlements had given way to a society equipped to live in Arctic conditions.

A debate that shaped modern environmental history. Norse Greenland became a famous example in arguments about climate and collapse, especially through Jared Diamond’s 2005 book. Archaeological responses have emphasized adaptation under several converging pressures. That approach also helps frame the Mexica case later in this atlas, where a 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 lay. Danish and Norwegian rulers later renewed the search, sometimes expecting to find Norse descendants. Voyages from the sixteenth to the eighteenth centuries eventually led to Danish colonization from 1721, discussed in the epilogue. The Skálholt map, drawn in Iceland around 1570, shows geography preserved through written memory.

DISCUSSION QUESTION

To what extent were the Greenland Norse victims of the Little Ice Age?

The Little Ice Age made life harder, but it did not act alone. Cooling and drying narrowed the margin for producing hay, and drift ice made voyages more difficult. The Norse responded by obtaining much of their food from the sea, especially seals; Inuit expansion in the same centuries shows that people using different technology could live in Greenland. At the same time, weaker ivory trade, plague in Norway and the loss of regular shipping reduced the income and contact on which the colony depended. Following Dugmore and colleagues, most scholars describe a convergence of pressures on a community too small to absorb them all. Evidence for orderly farm departures suggests that many people chose to leave. Climate could work slowly, narrowing alternatives until departure became sensible.

AN INTERESTING FACT

In 1921 Poul Nørlund excavated the churchyard at Herjólfsnes, where permafrost had preserved woolen gowns, hoods and caps. One tall cap resembled fashion at the fifteenth-century Burgundian court and was taken as evidence that Greenlanders followed European fashion after 1500. Radiocarbon dating placed it instead around 1280–1380, about two centuries earlier than that interpretation suggested. Other grave clothes from the churchyard date to about 1430, the latest firm evidence of Norse people in Greenland.

CHAPTER 6 · c. 1100–1450 · 1450

What the Norse Left

A shipbuilding skill could outlive the purpose for which a particular ship was made. The clinker method joined overlapping planks and served builders of warships as well as cargo vessels. Skuldelev 1, for example, was a 16-meter ocean-going pine ship built in western Norway around 1030. Later, broad trading vessels carried fish and grain. Builders could alter the size and use of a boat while retaining the craft itself.

Nordic coastal communities kept that craft alive into the twentieth century. In 2021 UNESCO recognized Nordic clinker boat traditions as intangible heritage. The political world of raiding had changed, but people still needed boats for fishing, transport and trade.

Stockfish found a durable market by using the conditions of the northern coast. At Vágar around the Lofoten islands, fishermen caught spawning cod each winter and hung the fish on racks. Cold, dry wind preserved it without salt, producing food that could be stored and carried for years. A catch made far north could therefore reach buyers much farther south.

The evidence for that market comes from discarded bones as well as merchants’ records. James Barrett and colleagues found a sharp rise in sea-fish bones at English sites around 1000, calling it the fish event horizon. Chemical analysis connects some cod consumed farther south with Arctic Norway. By about 1360 German merchants of the Hanseatic League maintained a permanent office at Bergen. Christian Keller estimates that Greenland’s 1327 shipment of walrus tusks was worth nearly 60 tonnes of stockfish: ivory was valuable, while fish supplied a staple trade on a large scale.

Iceland and Greenland had Norse settlers, Christianity and Norwegian rule after the 1260s in common, but they possessed different resources. Iceland may have had 40,000–60,000 people around 1100, an estimate based on 4,560 tax-paying farmers. It could sell wool and stockfish and survived plague, volcanoes and poverty. Greenland had roughly a twentieth of Iceland’s population; hay for its livestock and ivory for imports came under pressure together.

Church connections could not remove the distance. Greenland had a bishop at Garðar, appointed in 1126, and belonged from 1153 to the archbishopric of Niðaróss, a province administered from Trondheim like a regional headquarters. Those ties linked Greenland to European Christianity, but clergy, goods and messages still needed ships to cross the sea. Iceland’s greater population and wider range of resources gave it more ways to endure the colder centuries.

WHY IT HAPPENED

Versatile technology survives changing purposes. Clinker construction could be adapted to vessels from rowing boats to ships 30 meters long. Warships, cargo ships and fishing boats used the method, much as a modern truck can serve several trades. When raiding declined, fish, timber and grain still needed transport. The skills and investments in timber and wool retained value because builders could answer new demands.

Cod suited a colder sea. Cod thrive in cold water and gather to spawn off Lofoten each winter. The same northern conditions that troubled farms near the edge of their range helped fishers preserve their catch: cold, dry wind dried the fish without expensive salt. Stockfish could then travel to distant markets, making the climate an asset to the trade.

Iceland’s size and variety gave it resilience. Around 1100 Iceland may have had 40,000–60,000 people supported by livestock, fishing and trade. Its size and range of activities helped it endure disasters, though at great cost. The plague of 1402–04 did not end the society; older estimates put the death toll at half or more, while recent studies suggest about a quarter to 45 percent. Greenland, with roughly a twentieth of Iceland’s population, had fewer farms and trades across which to absorb losses.

Greenland depended on one export and one link. A few ships from Bergen brought Greenland iron, timber and grain, paid for almost entirely with walrus ivory. When European buyers turned again to elephant ivory, the principal export became less reliable. The royal ship then sank in 1369 and was not replaced. The colony faced trouble both earning imports and bringing them across the sea.

WHAT IT CHANGED

Norway becomes a fish economy. Northern Norwegian stockfish shipped through Bergen remained one of Norway’s largest exports for the next five centuries. German merchants connected it to their networks for centuries, and Bryggen’s wooden merchant houses survive as a UNESCO World Heritage site. Fishers had found profit in northern conditions that made Greenland’s farming harder.

Iceland endures as a fishing and farming society. Under Norwegian and later Danish rule, Iceland grew poorer during the colder centuries, yet its language, law codes and saga literature survived. Manuscripts including the sagas of the Vinland voyages became major sources for later Europeans studying the Norse Atlantic. Their survival was also a legacy of the Althing’s culture.

A second experiment begins far to the south. As Greenland’s last Norse farms emptied, the Mexica of central Mexico were completing an empire organized around a dense, engineered landscape and tribute from a wide region. Chapter 7 takes up this different arrangement. It asks what concentration and engineering could accomplish in a demanding environment, after the Norse case has explored mobility and dispersal.

DISCUSSION QUESTION

Which Norse innovation was most significant in the long run: the ship, the stockfish trade or the Althing?

The answer depends on the kind of significance we have in mind. Ships made settlement and exchange possible, carrying people to Iceland and Greenland and later carrying fish and grain. Their building tradition lasted into the twentieth century. Stockfish had the greatest economic weight after about 1100, linking a cold sea to lasting markets in England and the Hanseatic towns. The Althing has a different claim: Iceland’s tradition of law and assembly outlived independence and helped shape its modern parliament. One defensible choice is the ship, because it enabled settlement and trade, while stockfish sustained northern societies through the colder centuries. The ship’s long life also shows how a useful technique can find work beyond its original purpose.

AN INTERESTING FACT

In 1831 a hoard came to light near Uig on the Isle of Lewis in the Outer Hebrides. Its 93 pieces included 78 chessmen, 14 round playing pieces and a belt buckle. Carved around 1150–1200, probably in Trondheim, they were made mostly from walrus ivory, with some whale teeth. Among the kings, queens and bishops are warders biting the tops of their shields. Eighty-two pieces are in the British Museum and eleven in National Museums Scotland; much of the ivory may have come from Greenland’s Norðrseta hunting grounds.

CHAPTER 7 · 1325–1428 · 1428

An Empire Built on a Lake

The Mexica arrived in a basin whose inhabitants already knew both the uses and the dangers of water. Depending on where its rim is drawn, the Basin of Mexico covers 7,500–9,600 square kilometres. Its lakes could join into one sheet in wet years and separate as they shrank in the dry season. Most rain fell from June to September; a late beginning or an early frost could ruin the maize harvest. Water draining into the lowest lake, Texcoco, left salt behind as it evaporated. Springs below the southern mountains supplied fresh water to Xochimilco and Chalco. People there had made chinampas, raised fields built from material piled up from the shallow lake bed. The newcomers inherited this knowledge as well as the basin’s uncertain rainfall.

Their own accounts tell how they came to occupy the marsh. Mexica chronicles describe a long migration from Aztlan, a stay at Chapultepec’s springs in the late thirteenth century, and expulsion by stronger neighbours around 1299 or later. They then served Culhuacan, until a violent break drove them onto the islands. Tradition dates Tenochtitlan’s founding to Two House, 1325: the Mexica calendar named years by combining numbers and signs. Around 1337 their kinsmen founded Tlatelolco on a neighbouring island. Later rulers reshaped these accounts, but they agree on the newcomers’ poverty and outsider status. They had to make a home on land others had left to them.

The founding image in the Codex Mendoza gives that beginning a different dignity. Painted by Indigenous artists for the Spanish viceroy after the conquest, it shows an eagle on a cactus at the centre of an island divided by canals. The image tells us how the city’s beginnings came to be presented; it also invites us to ask how people survived there before they possessed an empire.

The island site gave a weak community advantages. Armies found it defensible, canoes could reach the shores, and fish, waterfowl, insects, salt and edible green algae supplemented the little farmland. Drinking water was another matter: there were no springs on the islands. Canoes brought water from Chapultepec until a flimsy clay-and-reed channel was built under Chimalpopoca in the 1420s.

The Mexica lived under Azcapotzalco’s authority, paying tribute in goods and labour and fighting its wars. When its ruler Maxtla turned against them, Itzcoatl joined forces with Nezahualcoyotl, the exiled heir of Texcoco, and the Tepanec town of Tlacopan. Their victory in 1428 brought a new arrangement: the three cities shared conquest and tribute, rather like shareholders in a company. The people who had taken refuge in the marsh now held power over the lake and its shores.

WHY IT HAPPENED

A closed basin made salt and floods inevitable. Water draining from the mountains had no river outlet from the basin. Evaporation removed water and left salts, especially in low-lying Texcoco; in wet years the level of the connected lakes rose. Settlers could use the lakes, but they also had to contend with salt and floods. These conditions would shape Mexica engineering for a century.

Latecomers took the marginal land. Established cities such as Azcapotzalco, Culhuacan and Texcoco already held the best farmland on the shores when the Mexica arrived in the thirteenth century. After expulsion from Chapultepec and Culhuacan, the newcomers found refuge on islands in the western marshes that others had not claimed. Their later power grew out of this weakness, helping explain the value they placed on military service and organised labour.

Service to Azcapotzalco taught war and politics. Azcapotzalco’s authority imposed tribute and military service on the Mexica for about a century. Campaigns across the basin gave them experience, while marriages connected them to powerful families. They also saw how a dominant city drew tribute from others. When Tezozomoc died in 1426 and his Tepanec kingdom split, that experience could be turned against their overlords.

An alliance of the threatened. Maxtla’s enemies had reasons to set rivalry aside. He threatened the Mexica and Nezahualcoyotl, whose father the Tepanecs had killed in 1418; some Tepanec towns, including Tlacopan, also opposed him. A common danger brought them together. Like later alliances formed against a shared enemy, their coalition would become an instrument of expansion.

WHAT IT CHANGED

A Triple Alliance to share tribute. The partners campaigned together and, according to later chronicles, divided tribute in shares: two-fifths each for Tenochtitlan and Texcoco, one-fifth for Tlacopan. Within a few years they subdued Xochimilco, Cuitlahuac and other southern lake towns. The alliance gained both the basin’s best chinampa land and the labour of those who farmed it.

Engineering the lake becomes possible. Rulers who could call workers from towns around the lake could attempt larger defences and water supplies. Chapter 8 follows two such works: the masonry aqueduct from Chapultepec and Nezahualcoyotl’s great dike of about 1449. Their labour depended on the political power gained in 1428.

Expansion beyond the basin. Azcapotzalco’s defeat gave the alliance access to tribute networks beyond the basin. Itzcoatl and his successor Moctezuma I then sent campaigns south into Morelos and north into Otomí lands. The growing empire would bring maize, beans and cloth to Tenochtitlan from hundreds of kilometres away, while creating enemies as well.

DISCUSSION QUESTION

Was the lake more of an advantage or a burden to the Mexica in their first century?

For the small and vulnerable community of the first century, the lake was mostly an advantage. It offered protection, food and canoe transport, allowing numbers to grow despite scarce farmland and the absence of draught animals. The islands had no springs, however, and the closed basin brought salt and flooding. Those burdens remained manageable while the city was small and under Tepanec rule, with no large labour force at its command. After 1428, power over the shores let the Mexica enlarge the city and engineer the water. More people could benefit from the lake, but more also depended on its uncertain level.

AN INTERESTING FACT

The Codex Mendoza reached Oxford by a circuitous route. Samuel Purchas reported that French privateers captured it on its way to Spain. It came into the hands of André Thevet, cosmographer to the French king, who signed it in 1553. The English geographer Richard Hakluyt bought it in Paris, and Purchas published woodcuts of its pages in 1625. Later it belonged to John Selden, whose books entered Oxford’s Bodleian Library in the 1650s. It remains there as MS. Arch. Selden. A. 1.

CHAPTER 8 · 1428–1500 · 1499

Water: Dikes, Aqueducts and Floods

A flood in the growing city presented Moctezuma I with a problem that could not be solved by moving a few houses. Chroniclers report that several wet years raised the lake over Tenochtitlan, usually dating the event to around 1449. The ruler asked Nezahualcoyotl of Texcoco to design a barrier. Workers came from Tlacopan, Culhuacan, Iztapalapa, Tenayuca and Xochimilco, bringing stone and clay to build a wall between closely driven stakes. It ran from Atzacoalco to Iztapalapa. Later writers assumed gates let water through, but Josefina García Quintana and José Rubén Romero Galván found no evidence for them.

The dike did more than protect the island. By separating saltier eastern Lake Texcoco from the western lagoon, known as the Lake of Mexico, it made the latter fresher. This changed what people could grow near the city: they could build more chinampas, raised fields made from material piled up from the shallow lake bed. Flood defence and agriculture depended on the same barrier.

Drinking water required another journey across the lake. Tenochtitlan had no springs, and the clay-and-reed channel built from Chapultepec in the 1420s repeatedly failed. Moctezuma I ordered a replacement, again with Nezahualcoyotl’s advice. Begun around 1454 and operating by 1466, its channels of tightly packed earth and mortar ran beside the Tlacopan causeway. Spanish observers later described water flowing through one channel while the other was cleaned. At the city’s edge, sellers took the water by canoe to customers.

Both projects depended on political authority. Thousands of workers had to be summoned from many towns before the rulers could turn their plans into a barrier or a water supply. The completed works displayed that authority, while giving the city room to grow.

A succession of bad harvests showed the limits of such control. Chronicles describe rain, hail and early frosts followed by drought; the tree-ring-based Mexican Drought Atlas confirms a great drought in 1452–54. In 1454, One Rabbit in the Mexica calendar, people sold themselves or their children to the Gulf coast Totonacs for maize. Moctezuma I opened the royal granaries. The disaster also pushed the alliance toward conquest in the warm, wet Gulf lowlands, where it could seek another source of food.

A later attempt to supply more water brought danger into the city itself. In 1499 Ahuitzotl brought the powerful Acuecuexco spring to Tenochtitlan despite warnings from Tzotzomatzin, ruler of Coyoacán, who was killed for them. Water broke out and flooded the city until divers sealed the spring. The more ambitious water system could serve more people, but it could also fail on a larger scale.

WHY IT HAPPENED

Floods drowned the growing city. A run of wet years raised water across the islands of the closed basin; chronicles report a flood around 1449. By then tens of thousands lived in a city with temples and palaces. Moving away was a much larger undertaking than it would have been for a small village. The investment in Tenochtitlan made protection necessary and helped bring about the dike.

Salt water limited the farms around the city. The lagoon beside the city formed part of salty Lake Texcoco. Brackish water limited the crops people could grow on chinampas there. A barrier against the saltier eastern water promised a fresher lagoon as well as flood protection. After 1449 fields could expand near enough for produce to reach the city fresh by canoe.

An island without springs needed piped water. The island had no springs, so its inhabitants depended on Chapultepec on the western shore. As the city grew, canoes could no longer carry enough drinking water, and the first clay-and-reed channel failed repeatedly. The replacement, operating by 1466, made a larger city possible: water reached palace fountains and sellers carried it by canoe to every district.

Power over many towns supplied the labour. Stone came from quarries leagues away, timber supplied the stakes, and thousands of people provided the labour. A single town could not furnish a project on this scale. The Triple Alliance’s victory in 1428 gave it authority to summon workers from Tlacopan to Xochimilco. Like a modern dam requiring a state to assemble money and labour, the waterworks depended on political power and made that power visible.

WHAT IT CHANGED

Fresher water allows new chinampas. As the lagoon became fresher, chinampas spread around the island and south toward Iztacalco and Mexicaltzingo; the map shows fields there after 1469. Food grown near the city could support more people. Chapter 9 examines how these fields, tribute and markets together fed perhaps 200,000 inhabitants. The farms depended on the water engineering that made cultivation possible.

Food security drives conquest. A harvest failure across the basin could leave the city hungry, as the famine of 1450–54 showed. Alliance armies subsequently campaigned toward the warm, rain-fed Gulf coast, including Cuetlaxtlan, and received food and cotton as tribute. Conquest thus offered one form of insurance against the high basin’s climate. The empire map paints tribute provinces tan, reaching both coasts by 1500.

An engineered lake becomes a trap. The city relied on dikes, causeways and aqueducts that an enemy could attack. In the 1521 siege Spanish brigantines broke through the dike and Cortés’s Indigenous allies cut the Chapultepec aqueduct, depriving residents of water. Causeways and canoe routes also concentrated movement where attackers could contest it. Chapter 11 follows how structures that had supported the city became vulnerable points in war.

DISCUSSION QUESTION

Did the Mexica control their environment, or did their engineering simply increase the risks they faced?

The Mexica gained real control: the dike checked floods and freshened the lagoon, the two-channel aqueduct supplied drinking water, and royal granaries cushioned famine. But frost and drought still destroyed harvests in 1450–54, and the Acuecuexco flood of 1499 exposed the danger of adding water to a closed basin. Engineering also made a larger city possible, so a failure could harm more people. Historians of risk call the resulting pattern the safe-development paradox: protection encourages people and investment to concentrate, increasing the cost of a later disaster. The Mexica managed their environment more effectively than their predecessors, within limits they did not fully understand.

AN INTERESTING FACT

Nahuatl preserved the famine of 1454 in two expressions. That year was Ce Tochtli, One Rabbit, in the Mexica calendar; sources say its people had been “rabbited”, necetochuiloc, meaning that they suffered famine. They also say people “became Totonacs”, because many fled or were sold to the Totonac lands on the Gulf coast in search of maize. A calendar name and a neighbouring people’s name carried the memory of hunger and flight.

CHAPTER 9 · c. 1430–1519 · 1515

Chinampas: Feeding a City

Farmers had refined the chinampa long before the Mexica gained control of the southern lakes. They dug canals through shallow water and piled mud and plants into long rectangular beds. Stakes held the beds in place, as did ahuejote willows, whose roots bound their edges. Seedlings started in nurseries of mud cut into small blocks; once transplanted, they left room for further crops. This careful use of space and water paid off. Studies summarized by José Luis de Rojas and Juan José Batalla put maize yields at about 3,000 kilograms per hectare, compared with 1,000–1,400 on ordinary fields. The surrounding water also moderated temperatures, giving crops some protection from the frosts that threatened rain-fed maize.

Control of the freshwater lakes brought this farming system into the orbit of the growing capital. The alliance conquered Xochimilco around 1430 and Chalco by about 1465. Many historians think that the state subsequently organized a substantial expansion of the fields. Pedro Armillas’s 1971 mapping from aerial photographs revealed a southern chinampa zone much larger than previously thought; estimates commonly put it at 9,000–12,000 hectares. Building it took labor on a remarkable scale. Lee Arco and Elliot Abrams estimate 25 million person-days over forty years, a person-day being one person’s work for one day. Local communities could have done the work, perhaps under state direction. Jeffrey Parsons estimated that the fields could feed 100,000 people or more—a large contribution, though not enough for the entire capital.

Other supplies reached the city through the market and tribute. At Tlatelolco, Bernal Díaz recalled, soldiers familiar with Rome and Constantinople said they had never seen a market so large, orderly and crowded. Cacao beans paid for small purchases, and cotton cloaks called quachtli paid for larger ones; a cloak was worth about 65–100 beans. The Codex Mendoza records provincial obligations like a tax register and depicts 42 great grain bins, although historians dispute their capacity and how often they were filled. The number of people to be fed is uncertain too: estimates range from under 100,000 to over 300,000. Michael Smith’s estimate of 212,500 on 13.5 square kilometres lies within the common range. Whatever the exact shares, the island city relied on food grown beyond its own ground.

WHY IT HAPPENED

Frost and unreliable rain threatened ordinary fields. The basin’s altitude exposed maize to two dangers. Above 2,200 metres, a September frost could arrive early, while summer rains could fail, as they did in 1452–54. Chinampa beds had moisture rising from below, and the water around them moderated the cold. Their location in the shallow lakes thus answered both problems, much as irrigation helps farmers through a dry season, although it could not prevent every crop failure.

The dike freshened water for new fields. Fresh water was indispensable: salt kills crops. Chinampas therefore flourished in the spring-fed southern lakes. Around 1449 Nezahualcoyotl’s dike helped separate the western lagoon from salty Lake Texcoco, making more water around Tenochtitlan suitable for cultivation. By 1469 the map shows fields south of the city. A work built for flood control also helped create conditions for the later fifteenth-century expansion of farming.

Conquest gave the state control of the best water. The freshwater farming zones belonged to communities the alliance first had to defeat. It took Xochimilco and neighboring lake towns around 1430 and the Chalco confederation by about 1465, after decades of war. The victories gave the capital access to both fields and the labor of their communities. Arco and Abrams estimate 25 million person-days over forty years for the southern fields; local communities could have supplied that work, perhaps under state direction. How far the state directed it remains debated.

A growing city needed food on a scale no island could supply. A few thousand people lived in Tenochtitlan in the 1300s. By 1519 the number may have reached 150,000–200,000 or more on an island of about 13.5 square kilometres. Growing food intensively in the lake helped, but the city still needed supplies from elsewhere. Canoes carried nearby produce, markets gathered goods from many communities, and tribute reached beyond the basin. The search for supplies accompanied expansion toward the warm, wet Gulf coast.

WHAT IT CHANGED

One of the world’s largest cities. The scale of the city astonished Spaniards who arrived in November 1519. Tenochtitlan and Tlatelolco together probably housed 150,000–200,000 people or more, exceeding any city in Spain. Food made such a concentration possible. Chapter 10 considers the other demands of island life: organizing water, streets, canals and waste for its inhabitants.

A food supply tied to empire. Food from distant communities helped sustain the capital, but those connections could also be broken. Provinces might rebel against tribute, and enemies could cut routes. In 1521 former subjects joined the Spaniards and blockaded the lake, turning the city’s dependence into a vulnerability during the siege described in Chapter 11.

A technique that outlived the empire. Chinampa farming survived the conquest of the empire. Fields at Xochimilco still supply vegetables and flowers in parts of southern Mexico City and form part of a UNESCO World Heritage site. Chapter 12 follows this longer history: the technique continued after the state that expanded it had fallen.

DISCUSSION QUESTION

How far did the chinampas, as opposed to tribute and trade, make Tenochtitlan possible?

The chinampas gave the city a substantial supply close enough for fresh produce to travel by canoe. Their moisture and frost protection made harvests more reliable, and estimated maize yields were perhaps three times those of rain-fed fields. The southern zone expanded after Xochimilco and Chalco were conquered. Parsons estimated that chinampas could feed perhaps 100,000 people or more, but many estimates put the city’s population at 150,000–200,000 or higher. The difference had to be made up through exchange and tribute, including grain, beans and cotton from distant provinces. We cannot calculate exact shares while the cultivated area, population and tribute volumes remain uncertain. The city depended on several connected sources, and disruption to those connections threatened its food supply.

AN INTERESTING FACT

Cacao beans were small change in basin markets, and they attracted counterfeiters. The sixteenth-century Florentine Codex, compiled under the friar Bernardino de Sahagún, describes sellers who emptied beans and filled the shells with earth or other material so they would pass as good cacao. The deception worked on the same principle as a counterfeit coin: the appearance of something valuable concealed a substitute.

CHAPTER 10 · c. 1430–1519 · 1519

The Planned City

At the heart of Tenochtitlan stood a sacred precinct roughly 430–460 metres across. Bernardino de Sahagún’s informants listed 78 structures within it. The largest was the Templo Mayor, a pyramid with shrines to Huitzilopochtli, god of war and the sun, and Tlaloc, god of rain. Rulers enlarged it repeatedly: excavations led by Eduardo Matos Moctezuma since 1978 have identified seven major building stages. The city around this religious center was divided into four quarters, Moyotlan, Teopan, Atzacoalco and Cuepopan, with causeways leading north, west and south. Within the quarters were about seventy calpolli. These neighborhoods, each with temples, schools and officials, gave the capital manageable units of local government, much like boroughs.

The plan had to make the lake useful while controlling its dangers. Canals beside many streets carried canoes to house doors and helped drain rainwater. The causeways shown radiating from the island had gaps for the flow of lake water, crossed by wooden bridges that could be removed in defense. Drinking water came by a different route. The dashed blue line on the map traces the aqueduct from Chapultepec in the west; its water followed the Tlacopan causeway to the precinct, and canoes carried it for sale in other districts. Díaz described reed latrines beside roads and waste sold from canoes for tanning. Much waste also fertilized the chinampas. Keeping wastewater apart from drinking water helped make the city healthier than many contemporary European towns.

On 8 November 1519, Moctezuma met Cortés at Huitzillan, near the southern entrance. The dark arrow follows the Spaniards’ route into the capital. Their descriptions give us an account of the city, but their purposes matter. In his second letter to Charles V, sent in 1520, Cortés described a city on a salt lake, its causeways, a two-channel aqueduct and a market where he estimated more than 60,000 people traded daily. Díaz, writing decades later, recalled soldiers wondering whether the sight was a dream. Both wanted to impress Spanish readers. Read with that purpose in mind and alongside archaeological evidence, their accounts reveal an exceptionally large and organized city.

WHY IT HAPPENED

Life on water demanded planning. On an island in a shallow lake, adding a house meant first making ground for it. Builders raised lots from the lake bed and connected them to canals, which provided transport and drainage. Chinampas spread outward in regular rows, while streets and waterways served the growing settlement. The setting encouraged order, even though the extent of central direction in residential districts remains disputed.

Hydraulic works made a large city possible. Growth depended on waterworks that addressed two different needs. A dike built around 1449 protected the island from flooding and helped freshen the lagoon. By 1466 an aqueduct brought drinking water from Chapultepec to a city without springs of its own. These mid-fifteenth-century works supported expansion far beyond the early settlement, to perhaps 200,000 inhabitants by 1519.

Tribute paid for monumental building. The monumental capital drew on resources far beyond its center. Temples, palaces and causeways needed stone, timber, lime and labor from the basin and beyond; tribute supplied materials and helped feed the workers. Successive rulers enlarged the Templo Mayor as a display of power. Its masonry made part of the empire’s wealth visible in the middle of the lake.

Religion organised space. The city’s center also had a place in Mexica religion. The Templo Mayor stood at the center of the cosmos, where earth met the heavens and the underworld, with shrines to Huitzilopochtli and Tlaloc. The four quarters reflected the four directions of the universe. This sacred order gave rulers legitimacy and residents a place within it. Religious and practical purposes shared the city’s spaces, though that does not establish a single sacred plan for every residential street.

WHAT IT CHANGED

A city the Spaniards would rebuild on. The conquerors built Mexico City over the ruins, but much of the earlier arrangement shaped what followed. Main causeways became streets; the cathedral and viceregal palace occupied the sites of the sacred precinct and Moctezuma’s palace. Elements of the grid remain in the historic center even though the lake has since been drained. Chapter 12 follows that later history.

The causeways become battle lines. The same causeways that brought travelers to the island concentrated armies on narrow routes. In the Spanish retreat of June 1520 and the siege of 1521, bridges and gaps designed to allow water through became deadly obstacles. Chapter 11 traces the fighting across the city’s connections to shore.

A model for later comparison. Modern discussions of sustainable cities often look to Tenochtitlan’s canals, aqueducts and reuse of waste. The comparison is striking: Europeans encountered an engineered urban system already more than a century old. Its construction and order also depended on tribute and forced labor, so the political system that supported the works belongs in the comparison.

DISCUSSION QUESTION

Was Tenochtitlan’s plan primarily a solution to environmental problems or an expression of political and religious power?

The plan served both purposes, often through the same works. Canals and streets allowed movement and drainage; the bridges, aqueduct and reuse of waste helped a dense population live on water. At the center, the sacred precinct and repeated enlargements of the Templo Mayor expressed religious and political authority, while the quarters and causeways related the city to the four directions. The connections ran deeper: rulers mobilized labor for hydraulic works, and a shrine to Tlaloc placed the rain god at the religious center. Historians still debate how much of the residential layout rulers directed and how much developed through neighborhoods. Tenochtitlan shows how environmental works can be built and maintained within political and religious institutions.

AN INTERESTING FACT

In the early hours of 21 February 1978, electricity workers digging behind Mexico City’s cathedral struck a carved stone at a street corner. It was a disc of pink andesite about 3 metres across and roughly 8 tonnes in weight, depicting the dismembered moon goddess Coyolxauhqui. The discovery led the government to demolish a block of colonial-era buildings. Archaeologists led by Eduardo Matos Moctezuma could then excavate the Templo Mayor beneath; the site now lies open beside the cathedral.

CHAPTER 11 · 1450s–1521 · 1521

The Flower Wars and the End of the System

Why did the Triple Alliance leave Tlaxcala and its neighbors outside its empire while fighting them repeatedly? The answer depends on whom we believe. Fernando de Alva Ixtlilxochitl says that in 1454, the last year of the great famine, rulers agreed to fight Tlaxcala, Huexotzinco and Cholula on fields usually near Atlixco. The combatants would take captives for sacrifice without taking each other's lands. Diego Durán credits the adviser Tlacaelel with the idea. Ross Hassig sees repeated fighting as a relatively cheap way to wear down strong enemies; Barry Isaac treats the ritual story as a later explanation for failure to conquer them. Meanwhile, tributary provinces encircled Tlaxcala. Tlaxcalans told the Spaniards that the blockade had deprived them of salt and cotton. Whatever the wars' purpose, their result was an independent neighbor with a long grievance.

Sacrifice also connected religious obligations to imperial politics. Mexica religion taught that the gods had sacrificed themselves to create the sun and needed human blood to keep the world moving. Many victims were war captives or tribute from subject peoples. The scale remains disputed: for the Templo Mayor's rededication in 1487, Durán gave 80,400 victims, while an Indigenous pictorial source gives 20,000; many historians consider the larger figures inflated. Since 2015 excavations of the great skull rack have identified 655 skulls, including women and children. When Cortés reached Cempoala in 1519, its Totonac ruler complained about Mexica tribute collectors. Tlaxcala fought the Spaniards and then allied with them in September. Existing enemies of the Alliance now had a way to act together.

The coalition's advance brought further violence. At Cholula in October 1519 Spaniards and their allies killed thousands, Cortés acknowledging about 3,000. They entered Tenochtitlan on 8 November. In May 1520 Pedro de Alvarado's men massacred celebrants at the festival of Toxcatl. The Spaniards fled along the Tlacopan causeway on the night of 30 June, suffering heavy losses; after the battle of Otumba they found refuge in Tlaxcala. From about October, smallpox brought by Pánfilo de Narváez's expedition swept Tenochtitlan for sixty days.

Cortés returned with fewer than a thousand Spaniards, tens of thousands of Indigenous allies and thirteen brigantines, small sailing warships built with Tlaxcalan help. From late May 1521 the attackers cut the aqueduct, contested canoe traffic and advanced along the causeways. These were the connections that had supplied a city of 200,000. Control of them allowed the besiegers to turn the lake's defenses against its inhabitants: hunger, thirst and disease accompanied the fighting until the city fell on 13 August.

WHY IT HAPPENED

Tribute and encirclement created enemies. The tribute that fed Tenochtitlan came from conquered communities that retained their own rulers. Totonac lords complained about its collectors. Tlaxcala remained independent, but tributary provinces surrounded it and, according to complaints recorded by Spaniards, cut it off from salt and cotton. The arrival of an outside force gave subjects and rivals an opportunity to change their position. Many joined the Spaniards within months.

Unfinished wars left strong rivals. Tlaxcala, Huexotzinco and the Tarascan kingdom had remained beyond Alliance control. Around 1478–79 a Tarascan army destroyed a Mexica force near Taximaroa; Durán's figure of more than 20,000 dead is probably inflated. Fortifications marked the frontier, including Mexica Oztuma and Tarascan strongholds. These undefeated states were potential allies for an invader. Tlaxcala proved especially consequential in 1520, when it sheltered Cortés's broken army and gave it a base for its return.

A new disease met a population without immunity. Smallpox reached central Mexico with Narváez's expedition in 1520. The disease had not previously reached the Americas, and people without immunity faced its rapid spread. Nahua accounts in the Florentine Codex describe victims so covered with sores that they could not move and others starving because no one could care for them. Cuitlahuac died after about eighty days as ruler. The epidemic weakened the city's defenders before the siege, while sparing the Spaniards, most of whom had survived childhood exposure.

The engineered lake had points of failure. An island city needed connections: causeways to land, an aqueduct for drinking water and canoes to carry food. A besieger could attack each one. The attackers severed the Chapultepec aqueduct at the start of the siege, while Spanish brigantines built on the lakeshore broke through the dike that had freshened the lagoon. Indigenous allies provided troops and knowledge of the targets. The works that made the city viable also gave its enemies places to interrupt its supply.

WHAT IT CHANGED

The fall of Tenochtitlan. Tenochtitlan fell on 13 August 1521, when Cuauhtemoc, its last ruler, was captured on the lake. Hunger, thirst, disease and violence had killed tens of thousands; chroniclers' totals of up to 240,000 cannot be checked. A plaque erected 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 only the beginning of a succession of epidemics. Cocoliztli struck in 1545 during a severe drought recorded in tree rings. Within a century central Mexico's population may have fallen by 80–90 percent, from an uncertain 5–25 million to about 1 million. Along with the devastation of families and communities came the loss of much of the labor that maintained the lake's dikes, canals and fields.

Spain inherits the lake. The Spaniards rebuilt on Tenochtitlan's ruins, but the basin's water problems remained. Much of the Mexica knowledge and labor used to manage them was lost within a generation. Floods in the following century led the newcomers to begin draining the lake. The epilogue follows that choice from the great flood of 1629 to the sinking of Mexico City today.

DISCUSSION QUESTION

Why did the Mexica system, so effective against the environment, prove so vulnerable to its human enemies?

The island concentrated perhaps 200,000 people where canoes and causeways could supply them. Those same connections could be blocked: the besiegers cut the aqueduct, fought along the causeways and used brigantines to contest the lake. The empire that fed the city through tribute had also made enemies among subjects and surrounded rivals. Their tens of thousands of troops gave the Spaniards a coalition capable of conducting the siege. Smallpox, a shock no Mesoamerican society could have anticipated, killed leaders and defenders beforehand. Historians differ in the weight they give Indigenous politics, disease and Spanish technology. Together these forces exposed a vulnerability in a system built to manage water, frost and food.

AN INTERESTING FACT

In the 1550s Tlaxcala's town council commissioned a great painted cloth, the Lienzo de Tlaxcala, that showed its warriors beside the Spaniards from their first alliance through the siege and later campaigns. The pictures had a practical purpose: the council sought recognition of Tlaxcala's loyalty and exemptions from tribute from the Spanish crown. The original is lost, but later copies, including one made in 1773, preserve an account in which Tlaxcalans are the heroes.

EPILOGUE · c. 1450–1521 AND AFTER · 1500

Two Answers to the Environment

Climate entered the two histories on different timescales. Relatively warm conditions around 950–1250 made farming possible in Greenland's fjords. Cooling after roughly 1275–1300, and drying near the Eastern Settlement, narrowed the margin on which farms depended. Greenlanders ate more seals and changed their trade as they adjusted to the pressures on their colony.

In the Basin of Mexico, the Mexica faced sudden shocks as well as longer periods of difficulty. Floods came in 1449 and 1499; frost and drought struck in 1450–54, with tree rings supporting evidence of drought in 1452–54. A longer drought from 1514 to 1539 overlapped conquest and epidemic. Waterworks and storage helped the Mexica respond, as did access to food from warmer lands. Climate mattered in both places, but neither society faced climate alone.

The resources available to meet these pressures were very different. Norse Greenland may have had 2,000–2,500 inhabitants, roughly the population of one of Tenochtitlan's seventy neighborhoods. The Basin of Mexico may have held 1–1.5 million. A large population could provide labor for dikes and chinampas—fields raised from the lake bed—and sustain supply networks that helped the Mexica survive famine. Yet feeding so many people also depended on connections a besieging army could attack.

In Greenland, by contrast, a lost ship, failed hay harvest or slump in ivory prices fell on a small community with limited reserves. Population did not determine either ending by itself. It affected the labor, supplies and connections available, and how much loss each society could absorb. The cost chart below shows the difference in scale.

The legacies extend beyond the settlements' endings. Inuit boats, harpoons and lamps suited life on sea ice; the Norse farming landscape at Kujataa, including Hvalsey, is now a World Heritage site. Iceland retained its law and literature. In Mexico Spanish authorities rebuilt the city and chose to drain the lake. They began the Huehuetoca tunnel in 1607–08, but in 1629, with it closed for repairs, heavy rain left the city flooded for about five years. Drainage continued for centuries. Today groundwater pumping compacts the old lake clay, and parts of Mexico City sink by up to about 50 centimeters a year. At Xochimilco, chinampas are still farmed. Communities could keep using some techniques even as the states around them changed.

WHY IT HAPPENED

Different environments demanded different answers. Grass and rich seas in the North Atlantic lay in scattered pockets separated by dangerous water. Ships, hunting and trade connected those resources. In the Basin of Mexico, a fertile lake system lay concentrated in a closed valley, where organized labor and waterworks could support cultivation. Each environment offered possibilities as well as difficulties, and the societies built different responses around them.

Scale shaped resilience. A few thousand people at most lived in Norse Greenland, compared with perhaps 1–1.5 million in the Basin of Mexico. The contrast mattered for labor, food storage and the losses a community could absorb. Mexica rulers could draw workers for dikes and raised fields and supplies from a wide area. A lost ship or poor hay harvest placed a burden on Greenland's much smaller population. Institutions and connections also shaped what each society could do with its people.

Single points of failure decided both endings. Walrus ivory was central to Greenland's exports, and ships from Bergen connected the colony to Europe. As trade declined, alternatives were limited. Tenochtitlan's dependence was concentrated differently: its aqueduct, causeways and canoe routes crossed one lake, where attackers could cut or contest them. These connections help explain the endings alongside climate, markets, alliances and disease.

Other peoples with different systems replaced both. As Norse settlements withdrew from Greenland, Thule Inuit communities expanded with equipment suited to sea ice. In Mexico, Spanish colonists and Indigenous allies defeated the Mexica state. The colonists brought diseases, livestock and different engineering, and their authorities later changed the lake system. Each environment could support more than one way of life, though each came with its own costs and possibilities.

WHAT IT CHANGED

Greenland becomes an Inuit land, then a Danish colony. Inuit communities had spread along Greenland's west and south coasts by about 1500. Danish colonization 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. In 2017 Kujataa, the farming landscape that includes Hvalsey and is associated with both Norse and Inuit farming, entered the World Heritage list.

The lake becomes a sinking city. One of the world's largest cities grew on the former lake bed. Pumping groundwater compacts its soft clay, and in some places, especially where that clay is thickest, the ground sinks by up to about 50 centimeters a year. Mexico City still faces flooding and water-supply problems. The challenge of living with water in a closed basin has endured for five centuries.

A question for the present. How can societies adapt to a demanding climate, and which responses will last? That question now faces people dealing with climate change. These histories suggest examining whether resources, places, people and institutions spread risk or concentrate it, and whether institutions can change with conditions. Students can test that argument against the evidence and the differences between the cases.

DISCUSSION QUESTION

Which society’s response to its environment was more successful, and by what standard should success be judged?

We need a standard before choosing a winner. By scale and achievement, the Mexica sustained Tenochtitlan, a city of perhaps 200,000, through dikes, aqueducts, chinampas and tribute; their networks helped them survive famine and flood. Norse Greenland held at most a few thousand people and was abandoned. By duration, the comparison changes: Norse Greenland lasted about 450 years, longer than the Mexica empire's century of dominance after 1428, and Iceland still has its assembly and literature. Both traditions also left innovations in use: clinker construction, stockfish and the Althing on one side, chinampas on the other. Neither ending can be attributed to climate alone. Economic and other pressures accumulated in Greenland; a coalition and epidemic confronted Tenochtitlan. A judgment of success should therefore identify its standard and consider the time over which a system worked and the human and natural shocks it faced.

AN INTERESTING FACT

When the Norwegian priest Hans Egede sailed from Bergen in 1721, he hoped to find descendants of Greenland's medieval Norse settlers and bring them into the Lutheran church. Scandinavians did not know whether they had survived. Egede found Inuit communities, learned their language and stayed to work among them. His first mission was on a small island. In 1728 the colony moved to the mainland under Governor Claus Paarss as Godthåb, now Nuuk, Greenland's capital. The mission intended for the vanished Norse became part of the beginning of Danish rule over the Inuit who lived there.