When Spain and Portugal conquered the Americas after 1492, they needed a huge, permanent workforce for mines and plantations. This section explains why Europeans turned to enslaved Africans rather than other labour sources, and how the trade was organised.
The core problem: labour: Silver mines (like Potosí) and sugar plantations needed constant, heavy labour. Colonists first tried to use indigenous people, then indentured Europeans — both failed to meet demand.
- Indigenous labour collapse — encomienda and mine labour, combined with disease (smallpox, measles) killed up to 90% of some indigenous populations by 1600, removing the main workforce
- Failure of European indentured servants — poor whites sent from Britain and France died fast in tropical heat, cost money to transport, and eventually gained freedom after their contract — colonists wanted permanent, hereditary labour
- Sugar's labour hunger — sugar cultivation and processing was brutally hard, dangerous, and needed year-round gangs; profits were so high that plantation owners would pay for a new labour source
- Existing African slave trade — Portuguese traders already bought and sold enslaved Africans along the West African coast from the 1440s, decades before Columbus — the infrastructure and trade routes already existed
- Racial justification — Europeans built ideas of racial hierarchy to defend enslaving Africans specifically, claiming (falsely) that Africans were suited to hard labour and heat
Exam focus: Paper 3 essays often ask 'To what extent...' — so don't just list reasons. Rank them: economic demand (sugar/silver profit) is usually the primary driver; disease and failed alternatives are the enabling conditions that made African slavery seem 'necessary' to colonists.
It's important to separate two different questions the syllabus asks: why slavery started (the causes above), and how colonial powers organised and expanded it once it began — which is covered next.
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Spain did not run its own slave-trading ships. Instead it used a licensing system called the *asiento — understanding this system is essential for explaining how* the slave trade was organised and who profited from it.
What was the asiento?: The *asiento de negros was a royal contract giving a person, company, or country the exclusive right* to sell enslaved Africans into Spain's American colonies. Spain itself had few slaving ships, so it sold this monopoly to others.
Portuguese asiento (1500s–1640)
Portugal held the first asientos, using its forts on the West African coast (like Elmina) to supply enslaved people directly to Spanish America.
Dutch involvement (1600s)
The Dutch West India Company broke into the trade by force, seizing Portuguese slave forts in West Africa and Portuguese sugar colonies in Brazil.
French asiento (1701–1713)
After Spain's Bourbon king Philip V took the throne, the French Guinea Company won the asiento as a reward for French support in the War of the Spanish Succession.
British asiento (1713–1750)
The Treaty of Utrecht (1713) transferred the asiento to Britain's South Sea Company — Britain became the dominant Atlantic slave trader of the 1700s.
P-D-F-B: Portugal starts it, Dutch muscle in, France profits from a marriage alliance, Britain wins it by treaty.
Use the asiento to show change over time: A strong Paper 3 answer shows the asiento shifting between powers as European rivalries played out — this is a great way to link Section 5 to the wider Anglo-French/Anglo-Spanish rivalry theme you meet elsewhere in this option.
| Colonial power | Main slaving regions | Main colonial product |
|---|---|---|
| Spain | Caribbean, Mexico, Peru | Silver, sugar |
| Portugal | Brazil | Sugar |
| Britain | West Indies, southern British America | Sugar, tobacco, rice |
| France | Saint-Domingue (Haiti), Louisiana | Sugar, indigo |
Each power's slave system had a different scale and intensity depending on what it was producing — sugar colonies (Brazil, the British and French West Indies) imported the most enslaved Africans and had the highest death rates, because sugar labour was the deadliest work in the Americas.
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Slavery reshaped New World economies and societies at every level — from royal treasuries in Madrid and London to the daily lives of enslaved families on plantations.
- Economic impact — colonial powers — sugar, tobacco and silver produced by enslaved labour became the most valuable commodities in world trade; port cities like Liverpool, Bristol, Nantes and Lisbon grew rich financing and insuring slaving voyages
- Economic impact — the 'triangular trade' — European goods shipped to West Africa bought enslaved people; enslaved people shipped to the Americas produced sugar/tobacco; sugar/tobacco shipped back to Europe — each leg of the triangle generated profit
- Economic impact — plantation economies — colonies like Saint-Domingue and Jamaica became so profitable from slave-grown sugar that European powers fought wars partly to keep or capture them
- Social impact — racial hierarchy — colonial societies were legally organised by race, with enslaved Africans at the bottom, free people of colour in a middle layer (larger in Brazil and the French colonies), and white colonists on top
- Social impact — family and community destruction — enslaved people were frequently sold away from spouses and children; laws in British America (e.g. Virginia, 1662) made a child's status (enslaved or free) follow the mother, guaranteeing slavery passed down generations
- Social impact — demographic transformation — in Brazil and the Caribbean, enslaved Africans became the majority of the population, permanently reshaping the ethnic and cultural make-up of these regions
Don't just describe — link cause to effect: A common weak answer describes the triangular trade without explaining why it mattered. Always connect: high sugar profits → colonial powers invest more in slaving voyages → demand for enslaved labour keeps rising → social structures harden around race to justify it.
Worked example — using evidence: By the 1780s, Saint-Domingue (French) alone produced around 40% of the sugar and 60% of the coffee consumed in Europe, using roughly 500,000 enslaved Africans — a single colony's profits rivaled entire national economies, showing how central slavery was to European wealth.
This economic and social foundation — profit-driven demand and a rigid racial hierarchy — set up the conditions covered in micro 19.5.2: the brutal Middle Passage crossing, plantation life, slave resistance, and the rise of abolitionism.