The Transatlantic Slave Trade and its Role in Colonial Expansion

The barbaric practice of slavery that came to underpin the European colonial project.

1441 AD
3rd millennium BC
Triangular Trade
4.9 million
Chattel slavery
Partus sequitur ventrem

The Emergence of the Transatlantic Slave Trade

When the Portuguese first began to establish trading posts in Africa in the 15th century, their primary objective was to obtain gold and other valuable commodities, such as ivory and spices.

As these trading ventures progressed, however, merchants soon became aware of the extreme profits that could be extracted from trade in human lives.

In 1441 AD, a man named Antão Gonçalves became one of the first recorded Europeans to buy an enslaved African, transported from the coast of Guinea, for the purpose of laboring on sugar plantations in the uninhabited São Tomé islands. Soon, Elmina Castle was transformed into a depot for slaves. This trafficking would eventually be extended to the Americas by the Spanish.

The Roots of African Slavery in the Transatlantic Trade

The transatlantic slave trade relied upon an existing practice of slavery and servitude.

Like much of Asia and Europe, enforced labor had been present in Africa throughout its history in diverse forms. Populated by regional empires and tribes, slavery in Central and West Africa was frequently the consequence of conflict, with prisoners of war exploited for labor, and sometimes profitably traded

Trade occurred both domestically and as part of the trans-Saharan slave trade, which had transported Africans to Europe and the middle east as far as back as the 3rd millennium BC.


The emergence of the transatlantic trade, however, transformed slavery in Africa. Faced with surging demand from European traders, African elites were increasingly incentivised to use warfare or raids against neighboring tribes to acquire slaves who would then be exported abroad via coastal ports like Elmina Castle.

At its peak, the Ashanti Empire in modern day Ghana is believed to have enslaved up to one third of its population.

Triangular Trade

The system that emerged for the sale of African slaves is often called Triangular Trade, which describes the three trading routes between three continents.


The first route was from Europe to Africa, where European traders would exchange goods such as cloth, guns, and alcohol for African slaves. These slaves were captured by African slave traders, who then sold them to European traders in exchange for European goods.

The second route involved the transportation of African slaves to the Americas, where they were sold to plantation owners in exchange for cash crops such as sugar, tobacco, and cotton. These crops were then transported back to Europe to be sold.

The third and final route involved the transportation of European goods back to Europe, where they were sold for a profit. This cycle of trade continued for several centuries and was responsible for the enslavement of millions of Africans.

The Middle Passage: The Brutal Journey from Africa to America


The journey for slaves from Africa to America across the Atlantic is historically known as the “middle passage”, and describes the middle leg of the triangular trade route. Weather dependent, it could take between one and six months.

The journey was carried out in large cargo ships known as “Guineamen”, and conditions were often horrific. A typical ship contained around 100 captives, chained in pairs using cuffs known as “bilboes”, and tightly into small spaces and subjected to extreme temperatures.

It is estimated that between 10 and 20 percent of captive passengers died from disease or malnutrition during the long voyages across the Atlantic Ocean, with mortality rate increased depending on the voyage’s length.

The Establishment of Slave Plantations in the Americas

The first slave plantations in the Americas were established in the early 16th century by the Portuguese, bringing the first African slaves to their colonies in Brazil in 1526.

The Treaty of Tordesillas, signed in 1494 between Portugal and Spain, gave Portugal the rights to colonize and trade in Africa, giving them a monopoly on the African slave trade and the ability to establish sugar plantations in Brazil using enslaved labor.


Over the course of the slave trade, an estimated 4.9 million enslaved Africans brought to Brazil alone.
The Spanish, who had established colonies in the Caribbean and Mexico, also relied heavily on African slaves for labor. In the Caribbean, sugar plantations were established on islands such as Cuba, Jamaica, and Hispaniola.

Slave labor was used for a variety of purposes: from the cultivation of sugar, coffee, rice, and cotton, construction and timber production, and the mining of silver.

The Royal African Company and the Slave Trade in the Caribbean


In the 17th century, British and French colonizers followed in establishing slavery-based economies in the Caribbean, bringing to work on sugar, tobacco, and other cash crop plantations.

A central player in the trade was the Royal African Company. Established in 1660 to trade in west Africa, including gold and ivory, the Company quickly focused exclusively on the far more profitable Slave trade.

By the 1680s, the Royal African Company was transporting around 5,000 slaves a year across the Atlantic. Over a period of 6 decades, this amounted to almost 200,000, around 40,000 of which died during the journey.

The Evolution of Slavery in English Colonies

The first slaves to arrive in English colonies were initially classified as “indentured servants”. In other words, they were contracted to labor for a certain number of years without pay. This included not only Africans, but Europeans – particularly prisoners.

By the mid 17th century, this system started to give way to “chattel slavery”, largely racially exclusive to Africans, in which individuals were considered the permanent property of their owners.


These slaves were traded in hubs including Charleston, South Carolina, and New Orleans, Louisiana. Slaves were brought to these cities from Africa and other parts of the Americas and sold at auction to plantation owners throughout the region.


The system of slave ownership in America upheld the legal principle of “partus sequitur ventrem”, first passed in Virginia in 1662, meaning that children born to an enslaved mother would also be considered a slave.

This meant that even if the father was free, their children were still subject to enslavement. The law of “partus sequitur ventrem” was adopted by many states in the US and remained in place until 1865 when it was abolished with the passing of the Thirteenth Amendment.

In addition to this legal framework, there were other methods used by slave owners to control their slaves. Corporal punishment was common, as was the threat of separation from family members through sale if they did not comply with orders. These tactics combined created an oppressive environment where resistance against slavery became increasingly difficult for those subjected to it.

The Abolitionist Movement in Eighteenth Century America and Britain


In the eighteenth century, slavery in America was faced with increasing support for abolition.

This emerged both as an ethical impulse following religious belief and Enlightenment principles of liberty, and for political reasons: the northern states were keenly aware of the south’s economic reliance on slavery. Abolition would therefore tip the balance of power in the north’s favor.

A milestone in the British abolitionist movement was the founding of the Society for Effecting the Abolition of the Slave Trade in 1787. This group sought to end slavery through public education, lobbying, and providing financial incentives to those who freed their slaves.

William Wilberforce led a successful campaign which resulted in Parliament passing legislation banning the slave trade, which came into effect on 1 May 1808.

Other countries followed suit over time: France abolished its own slavery in its territories in 1794, followed a year later by Denmark and Norway. In the United States, this culminated in the 13th Amendment to the constitution, abolishing slavery, in late 1865.

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