The Columbian Exchange
See what happened when two halves of the world that had been apart for thousands of years were joined: new crops for everyone, catastrophe for the Americas, and a chain of causes that ended in the Atlantic slave trade.
BEFORE
Two worlds with their backs to each other
When the ice age ended and the sea rose, the Americas were cut off from Africa, Asia and Europe. For roughly ten thousand years the two halves of the world went their own way. Both grew crops, built cities and states and roads, exactly as in lessons 1 to 3. But they did it with different plants, different animals and different germs.
Tenochtitlan, the Aztec capital, was one of the largest cities on Earth around 1500, and the Inca ran a road network as impressive as any in lesson 3. Neither had ever seen a horse, a cow, a wheel put to work, or an iron blade.
WHAT CHANGED
One voyage, and then ships every year
In 1492 Columbus sailed west from Spain hoping to reach Asia, and he died still believing he had. What he actually opened was a permanent two-way route. Within a generation, ships were crossing every year in both directions, carrying plants, animals, people and disease. The historian Alfred Crosby gave the whole process a name in 1972: the Columbian Exchange.
The important word is 'permanent'. Contact itself was not new. Norse sailors reached Newfoundland around the year 1000, built a small settlement and left again. What began in 1492 never stopped.
Check yourself
Norse sailors reached North America around 1000 CE, five centuries before Columbus, and almost nothing followed. Why did 1492 change the world when the earlier landing did not?
- The Norse found a nearly empty coast, with nobody there to trade with or sell to
- The Norse kept their discovery secret from the rest of Europe
- Columbus had better maps and knew exactly where he was
- The 1492 route was repeated every year by states and merchants who could pay
Show the answer
The 1492 route was repeated every year by states and merchants who could pay
Yes. A turning point needs more than a first. It needs the thing to keep happening. Spain, and soon its rivals, sent ships every year, and that steady traffic is what moved crops, germs and people.
What crossed the Atlantic
| Americas → Old World | Old World → Americas |
|---|---|
| Potato, maize, tomato, chilli, beans, cacao, cassava | Wheat, rice, sugar cane, coffee, bananas |
| Turkey, guinea pig | Horse, cattle, pig, sheep, chicken |
| Little: perhaps syphilis, still argued over | Smallpox, measles, influenza, typhus |
| Silver, in enormous quantities | Millions of people, most of them enslaved |
Check yourself
Where did each one start?
- Maize on the cob
- A herd of cattle
- Chilli in the cooking pot
- Bread made from wheat
- Smallpox
- Cacao beans for chocolate
Show the answer
Started in the Americas: Maize on the cob, Chilli in the cooking pot, Cacao beans for chocolate
Came from the Old World: A herd of cattle, Bread made from wheat, Smallpox
WHY ONE WAY
Where crowd diseases come from
Go back to lesson 1. Most of the great killers began as illnesses of herd animals kept close to people, and they can only keep going in large, dense populations that supply a steady stream of people who have never had them. Eurasia and Africa had cattle, pigs, sheep, goats, horses and chickens, plus cities linked by the roads of lesson 3 and the routes of lesson 4.
The Americas had llamas and alpacas in the Andes, turkeys, dogs and guinea pigs, and nothing like those herds. So the germs had been sorted thousands of years before the ships. Populations that had survived centuries of epidemics carried some resistance; populations that had met none carried none.
Check yourself
A few hundred Spanish soldiers brought down the Aztec and Inca empires mainly because their weapons and their courage were so much better.
Show the answer
False
False, and the real story is more interesting. Steel, guns and horses mattered, but two other things mattered more. Epidemics struck rulers, armies and farmers before and during the fighting: smallpox swept Tenochtitlan in 1520, and had already reached the Inca, whose ruling family was in the middle of a civil war over the succession. And local allies: tens of thousands of people who resented Aztec rule marched with Cortés. Whenever a tiny force beats a huge one, ask what else was going on.
What travelled east, and what it did
- The potato. From the Andes. It grows in cool, poor soil and yields more calories from a field than grain does in northern Europe. Historians credit it with a real share of Europe's population growth in the 1700s and 1800s.
- Maize, sweet potato and cassava. They grow where wheat and rice will not: dry hill slopes in China, thin soils across much of Africa. Populations rose on three continents.
- Flavour. Chilli reshaped the cooking of India, Sichuan, Korea and Thailand within about two centuries. Tomato did the same for Italy, Spain and Iran. None of these tastes is as old as it feels.
- Silver. Mines in Mexico and the Andes, worked largely by forced labour, poured silver into world trade, much of it ending up in China. Money itself was changed by it.
Check yourself
- A farming district in the 1700s lives on rye, oats, peas and some potatoes. One crop fails; people go hungry but nearly all survive.
- A farming district in the 1840s feeds most of its people on potatoes alone. A new plant disease destroys the crop two years running.
What does the pair tell you about a crop that feeds more people?
- American crops were a mistake and made life worse than before
- The crop that lets more people live also concentrates the risk they all share
- Plant diseases only attack crops that came from far away
Show the answer
The crop that lets more people live also concentrates the risk they all share
Yes. The potato let Ireland's population grow fast, and when blight arrived in the 1840s roughly a million people died and roughly a million left. The blight was the trigger; depending on one plant, and how land and food were managed, turned a crop failure into mass death. More food and more exposure are two faces of one change.
WHO WAS MOVED
The labour gap and the slave trade
Sugar, tobacco and later cotton, grown for European markets, needed enormous amounts of labour, and the Indigenous people whom colonists had first forced to work were dying in vast numbers. Europeans turned to the slave trade that already existed in Africa and expanded it beyond anything before. Between the 1500s and the 1800s roughly twelve million Africans were shipped across the Atlantic against their will. Around one in seven died on the crossing.
Most were taken to Brazil and the Caribbean to grow sugar. Slavery was not new; it had existed in Europe, Africa, the Islamic world and the Americas. What was new here was the scale, the fact that the status passed to your children for ever, and the way it was tied to skin colour.
Check yourself
Reza is asked why the Atlantic slave trade grew so fast in the 1500s and 1600s. Which answer follows the chain of causes best?
- European ships could now reach Africa, so a trade in enslaved people was bound to follow
- African states were too weak to stop it, so European traders simply seized whoever they wanted
- Plantations needed labour, the Indigenous population had collapsed, and slavery filled the gap
- Sugar can only be grown by people from Africa, for reasons of climate
Show the answer
Plantations needed labour, the Indigenous population had collapsed, and slavery filled the gap
Right. One catastrophe fed another. European demand for sugar, an Indigenous population destroyed by disease and forced labour, and then mass enslavement chosen as the answer. None of it was inevitable: each link was somebody's decision.
An exchange, but not an equal one
What the Old World received
Crops that fed hundreds of millions more people, silver that oiled world trade, land for its growing population, and profits that helped pay for the changes in lesson 8. Its population rose.
What the Americas and Africa received
Epidemics, conquest, forced labour, the loss of languages, records and whole ways of living, and centuries of slavery. The word exchange is accurate about direction and misleading about fairness. Even the gains cut both ways: Spanish horses that escaped onto the plains gave some Indigenous nations a powerful new way of life, which was then taken from them too.
Lesson recap
- After 1492 the Atlantic became a permanent two-way route, and two biological worlds that had been apart for about ten thousand years were joined.
- Old World crowd diseases, bred over millennia beside herd animals in dense cities, killed most of the population of the Americas within roughly a century.
- Maize, potatoes, cassava and chilli fed and flavoured the Old World, and silver and profit flowed the same way.
- The labour gap left by the collapse was filled by around twelve million enslaved Africans: a chain of causes, not an accident.
- Call it an exchange if you like, but always count who paid.