Norse and Aztecs questions and answers

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.

READ CHAPTER 1 — Medieval Warm Period and Little Ice Age →

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.

READ CHAPTER 2 — Viking expansion and the longship →

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.

READ CHAPTER 3 — Settlement of Iceland →

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.

READ CHAPTER 4 — Vikings in Greenland and Vinland →

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.

READ CHAPTER 5 — Why the Norse abandoned Greenland →

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.

READ CHAPTER 6 — Norse stockfish trade and legacy →

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.

READ CHAPTER 7 — Founding of Tenochtitlan →

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.

READ CHAPTER 8 — Aztec dikes, aqueducts and floods →

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.

READ CHAPTER 9 — Aztec chinampas →

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.

READ CHAPTER 10 — Layout of Tenochtitlan →

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.

READ CHAPTER 11 — Fall of the Aztec Empire →

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.

READ CHAPTER 12 — Norse and Aztecs compared →