The Atlantic slave trade from Africa to the New World might well have been the largest maritime migration in history. The reason for this maritime movement was to obtain labour as the indigenous population of the New World had declined rapidly because of its lack of immunity against imported pathogens. In total about 12 million Africans were forcibly embarked and because of the high mortality aboard, about 10 million slaves were disembarked in: Brazil (45%), the British, French, Dutch, and Danish Caribbean (37%), Spanish America (11 %) and North America (4%). In spite of the growing volume of the trade and the increasing demand for slaves, the Atlantic slave trade was abolished during the first decades of the 19th century due to humanitarian pressures.

Overview of the slave trade out of Africa
Number of slaves disembarked according to destination and century, 1500-1900.
Number of slaves disembarked according to destination and century, 1500-1900. Source :
Geographical origins of the African slaves.
Geographical origins of the African slaves. Source :

The expansion of Europe after 1500 could not have succeeded without slaves as Europeans refused to migrate in sufficient numbers to the tropics, where their death rate was extremely high. This is why the European colonizers in Africa and Asia bought local slaves. In the tropical parts of the New World, however, the supply of local slaves was insufficient, especially since it was the main region where the colonizing nations were able to produce tropical export crops such as sugar and coffee. The increasing demand for these products in Europe stimulated a large number of European shipping companies to buy slaves on the Atlantic shores of Africa, to ferry them across the Atlantic and to sell them to slave owners in the New World. Between 1500 and 1870, the slave trade across the Atlantic Ocean was to be one of the major human migrations in history as it changed the ethnic composition of the population in the New World dramatically. In total about 12 million Africans were forcibly embarked and because of the high mortality aboard, about 10 million slaves were disembarked in: Brazil (45%), the British, French, Dutch, and Danish Caribbean (37%), Spanish America (10. 7 %) and North America (3. 6%). The slave ships came from Portugal and Portuguese Brazil (47. 6%), Great Britain (25. 5%), France (10. 8%), Spain and Spanish America (8. 2%), the Netherlands (4. 4%), colonial North America/the USA (2.3 %) and Denmark and the Baltic states (0. 8%)

The cultural, demographic and economic foundations of the Atlantic slave trade

There were three reasons that shaped the demand and supply of slaves across the Atlantic, each situated in another continent. The first reason was the demand for labour in the New World, where the indigenous Amerindian population rapidly declined after the arrival of the first European explorers. It appeared that the Amerindians had no immunity against common diseases imported from the Old World such as the flu, the scarlet fever or even just a common cold. Some estimates put the decline of the Amerindian population at 40%. This enabled the invading Europeans to conquer large tracts of land without much opposition, but at the same time the New World settlements could only yield profits if sufficient labour was available. The demand for labour was particularly high in the tropical parts of the New World, where new products such as tobacco and sugar could be cultivated for export to Europe and North America. In order to obtain a sufficient number of labourers in their colonies in the New World, the Spanish and Portuguese enslaved some of the Amerindians in addition to bringing in slaves from their home countries, as African slaves were a common sight in Spain and Portugal. However, their number fell far short of the demand in the New World, while the European states, which started to establish colonies during the seventeenth century, such as France, England and the Netherlands, contained no slaves at all.

The second reason for transferring slaves from Africa to the New World was the fact that Europeans did not enslave one another in spite of their many vicious international and civil wars, the severe persecution of minorities such as the Irish and the Huguenots, and the large number of destitute people. True, some of the captives of the English conquest of Ireland, of the English Civil War and of the religious wars in France were forcibly sent to the Americas, but their numbers could not nearly satisfy the demand, and their children—if they had any—were free and could not be forced to become life-long labourers.

During the first decades of the English, French and Dutch colonisation of the New World, the need to obtain workers outside Europe did not arise immediately as it was possible to obtain temporary labour by contracts of indenture. In the ports of England, France, and the Netherlands, boys and young men with an adventurous spirit could sign a contract with an employer in the New World for a certain number of years in exchange for a paid passage to the colonies, food and housing. Between 1625 and 1660 at least 60,000 indentured labourers migrated to the West Indies, with Barbados as their main destination. In fact, this small Caribbean island rapidly became the most densely settled area in the New World with 77 settlers per square kilometre, while during the previous period of Spanish colonisation the Caribbean region hardly had counted one settler per hundred square kilometres. The sudden decline in the migration of indentured labourers after the 1650s was caused by those whose indenture had expired and who had returned to the ports in Europe from which they had departed. There, they spread the news about the wretched conditions, the hard work, the bad housing and food and the high mortality in the primitive and completely male pioneer societies in the colonial Caribbean. This caused a dramatic decline in the number of indentured migrants willing to go there and the European governments had no way of forcing their subjects to migrate overseas.

The third reason for the transfer of slaves from Africa was the fact that on that continent, slavery was widespread and the slave trade there had existed for centuries, and was well organized with markets, brokers and plenty of experience of how to move slaves from one area to another. Before the beginning of the Atlantic slave trade, the existing slave trades within Africa and to the Near East already comprised large numbers of slaves. This explains why the Europeans, once they had arrived on the West coast of Africa, only needed to offer more than the African and Arab buyers  to obtain as many slaves as they wanted. In part, the various slave trades did not overlap, because the European buyers wanted male slaves, while the slave owners in Africa and the Near East were looking for females, who could be employed in a much wider variety of economic activities than was customary for women in Europe. In addition female slaves were able to produce offspring for their owners.

The first Atlantic slave traders were the Portuguese as they had been the first to face a shortage of labour in their colony in the New World. The Spanish also experienced shortages, but they were not able to buy slaves in Africa as in 1496 the Treaty of Tordesillas instigated by the Pope had divided the non-European world in two parts: Africa, part of Latin America and part of Asia were given as a loan to the Portuguese crown and the other parts—many still not exactly delineated at the time—to Spain. This division made Spain dependent upon foreign merchants for the supply of slaves to Spanish America. It should be stressed that Portugal—with the exception of some parts of Angola—did not invade Africa, but only erected a string of forts along the coast, where trade was conducted and slaves and produce could be housed and stored awaiting shipment.

After 1600, the English, French and Dutch broke the Iberian monopoly in the Atlantic and also created colonies both in the moderate as well as tropical zones of the New World. For some decades, their demand for African slaves was far smaller than in the Iberian colonies because of the ample supply of indentured labourers. Of this second group of invaders, the Dutch were first to switch to slaves once they had conquered part of Portuguese Brazil in 1630. The French and English followed suit and each of these three countries concentrated their slave trading on a separate part of the African coast.  

After 1650, the colonists in the English West Indies changed from cultivating tobacco to sugar cane. This demanded much more manpower in addition to the purchase of expensive mills. As has been pointed out, at the same time it became increasingly difficult to obtain indentured labourers from Europe. For a couple of years, employers still could rely upon the arrival of Irish and royalist prisoners of war who had been sent to the West Indies as forced labourers, but after the end of the English Civil War in 1660, that supply dried up. No other groups in Europe could be forced to move to the West Indies, and thus the colonists and especially the first sugar cane planters in the English Caribbean had no other choice but to turn to Africa for slaves. Later their colleagues in the French, Dutch and Danish West Indies followed suit.

The English and French had started to trade in slaves well before 1660. The Navigation Act of 1651 disallowing foreign slavers to sell slaves in the English colonies proves that the early English slave trade was sufficient to provide the first sugar plantations in the Caribbean with slaves from Africa. Originally, the French planters relied on the Dutch slavers, who could no longer sell slaves in Dutch Brazil after it had been lost to the Portuguese in 1654. In 1658 the French founded their first slave trade company, the Compagnie du Cap-Vert et du Sénégal, and the English created a well-organised company with a monopoly on the slave trade in 1672, the Royal African Company. The Dutch had started their West-Indische Compagnie as early as 1621. However, in the Atlantic, large monopoly companies were not necessarily more efficient than smaller ones or even than individual merchants. Only the big and all-embracing Dutch West India Company could afford to attack Portuguese Brazil, an adventure that ended in bankruptcy. The English and French with their small-scale colonisation ventures, financed by a few merchants or shipping firms, seemed to have been more effective and achieved longer-lasting results than the Dutch.   

 The first slave trade circuit in the Atlantic was dominated by slave ships originating in Portugal and Portuguese Brazil. Yet, there was ample room for interlopers from England, France, and the Netherlands to smuggle slaves into Spanish America.  A new, second circuit consisted of slave ships from England, France, the Netherlands, Sweden, Brandenburg and even Lithuania. On the African coast, there was some overlap in the areas where the ships of both circuits traded in slaves, but otherwise these two slave trade circuits remained remarkably separate.

The second, circuit had its heyday during the eighteenth century, when more than 3 million slaves were landed there, while Brazil and Spanish America received a similar number of slaves during the 19th century. This difference reflects the difference in the demand for slaves, which in turn was based on the difference in the development of plantation agriculture. In the Caribbean, the expansion in the number and size of the plantations was most rapid in the English, French, Dutch and Danish colonies during the 18th century, while Brazil and Cuba peaked in the 19th century. The slave imports did not only fuel expansion, they also allowed the two plantation zones with slaves to offset the natural decline which was due to the high mortality. The only exception to this rule was North America, where the slave population experienced strong demographic growth, similar to that of the free population. This explains why around 1800 about 30% per cent of all slaves in the New World lived in the U.S., while this area had only received 3,6 % of the slaves disembarked in the New World.

Where did the slaves come from?

As the above table shows, all regions along the coast of West Africa participated in the Atlantic slave trade, but there were substantial shifts over time. The only area with a constant export of slaves was West Central Africa, which supplied about 40% of the total number of slaves embarked. The other extreme was the South-Eastern coast of Africa. It started to supply substantial numbers of slaves for the trade across the Atlantic only after 1800, when faster sailing ships could reduce the time needed to cover the extra mileage around the Cape of Good Hope and because the traditional export areas along Africa’s West coast were controlled by anti-slavery naval patrols.

As can be seen on the map, the area closest to the New World, Senegambia, provided only a relatively small number of slaves. This is indicative of the market for slaves in Africa, where the Africans decided how many slaves they wanted to sell, where they wanted to sell them, as well as their sex and age structure. The Europeans preferred able-bodied adult men as workers in the New World, but they had to conform to African norms and values and were forced to buy many more women and children than was normal among the free migrants to the New World. As a result, about 70% of women and 90 % of all children entering the New World between 1500 and 1800 were enslaved and came out of Africa.  

The mortality among the slaves ferried across the Atlantic was high, but declined over time especially on slave ships from England. Also, mortality varied according to the port of embarkation suggesting that slaves arrived on the coast in a physical condition that varied widely. As prices increased, it became profitable to extend the catchment area and when slaves originated further into the interior, the number of days that the slaves had to walk to the coast increased and which badly affected their physical condition. In times of drought and hunger, forcing African slave owners to sell some of their slaves into the Atlantic slave trade, the physical condition of the slaves also left much to be desired. Having a doctor on board reduced mortality somewhat, but this reduction declined during the 19th century, when many slaves were transported in illegal slavers without previous physical selection and without the services of a physician during the voyage.

Buying slaves on the African coast

The slave trade on the African coast could be conducted in three ways. When a slave ship from Europe, Brazil or North America arrived on the African coast, it could sail to one of the forts on the coast, preferably under the same flag as that of the ship. The commanders of such forts, as well as the African traders living in the vicinity, usually held a stock of slaves allowing the captain of the slave ship to arrive quickly at the number of slaves he intended to buy in total. However, this method was expensive as a substantial part of the trade goods brought from Europe had to be paid as commission to these intermediaries. Another way of buying slaves involved renting a piece of land on the shore from the local ruler on which a temporary shed would be constructed. These sheds served both as a temporary warehouse for trade goods as well as a market, where the African brokers would bring their slaves for sale. At the end of each day, the newly-bought slaves would be ferried to the ship and housed in its hold. The third and most used method for buying slaves was to sail along the coast and invite the African brokers with their slaves to come aboard. Most of the negotiations would be carried out on deck, where the broker would choose from the assortment of goods (such as guns, textiles, alcoholic beverages and household items), while the ship’s doctor would have a chance to make a superficial physical check of the slaves by looking at their teeth, skin, hair colour and general condition. Usually the brokers arrived only with a few slaves at the time, so this method could increase the time spent on the African coast to well over a year before the captain had obtained a sufficient number of slaves to make the crossing worthwhile.  

As slaves were not consenting passengers, probably about one in ten slaving voyages experienced a major rebellion, usually when the ship was still in sight of the African coast. This is why slave ships carried a larger crew than was strictly necessary for sailing the ship and more weaponry than was usual on other merchantmen. This reduced the growth of the slave trade, as higher costs meant higher prices and fewer buyers. In addition, the rebellions influenced the ethnic composition of the Atlantic slave trade as slave ships along the coast of Senegambia, the Windward Coast and Sierra Leone experienced more rebellions than ships buying slaves elsewhere.

The Middle Passage

In much of the older literature, the trip from Africa to the New World was usually described as the most lethal part of the voyage. The slaves were held in unsanitary conditions in the hold of the ship and could only spend a short time on deck, well shackled, weather permitting. As the trip from Africa to the New World, the so-called Middle Passage, could take six to eight weeks, the weakest slaves aboard (pregnant women and children) ran a high risk of dying and this certainly applied to small infants and children. More recently, however, it has been pointed out that the middle passage was only a part of a much longer ordeal because most slaves had to walk to the coast, and as this distance became longer over time, the mortality in Africa increased and the condition in which the slaves arrived aboard deteriorated. A similar mechanism increased the mortality of the crew. The slave ships spent an increasing amount of time sailing along the coast, and this extended the exposure of the crew to tropical diseases. The weak physical condition of both slaves and crew explains why there were not more shipboard rebellions.

Ending the Atlantic slave trade

During the last decades of the eighteenth century the number of popular voices opposing the slave trade increased, especially in Great Britain and the US, where new religious communities such as the Quakers, Baptists and Methodists started a campaign to outlaw the slave trade and slavery. In spite of the economic advantages of the slave trade, their campaign met with success in 1806, when a majority in both houses of the British parliament voted in favour of a law to make the slave trade illegal for British subjects as per March 1, 1808. However, as can be seen from table I, the slave trade continued to the end of the 19th century under the flags of those countries that had not outlawed the slave trade or in circumvention of these laws. In order to stop the illegal slave trade, Britain, France and the US stationed naval squadrons off the coast of Africa, but these ships were only able to  intercept a small percentage of the illegal slave ships. Because of the expansion of plantation agriculture, especially in Brazil and Cuba, the prices for slaves continued to rise in the New World allowing for higher profits, and this stimulated illegal slave traders to take greater risks and to invest in faster sailing vessels. Also, the slave trade within Africa increased as the suppression of the Atlantic trade lowered the price of slaves in Africa itself allowing more Africans to become slave owners. The last transatlantic slave voyage probably was made in 1867 to Cuba.

In the end, humanitarianism prevailed over economic self-interest. Europeans still did not rank Asians and Africans as equals, but they accepted that it was no longer permissible to trade and to own them. In this way, the ending of the slave trade and the abolition of slavery signified the beginning of the end of Europe’s overseas expansion.    

To quote from this article

Pieter Emmer , « The Atlantic Slave Trade », Encyclopédie d'histoire numérique de l'Europe [online], ISSN 2677-6588, published on 05/02/21 , consulted on 21/04/2024. Permalink :


Eltis, David, Richardson, David, Atlas of the Transatlantic Slave Trade, New Haven/London, 2010.

Pétré-Grenouilleau, Olivier, Les traites négrières. Essai d’histoire globale, Paris, Gallimard, 2004.

Klein, Herbert S., The Atlantic Slave Trade, Cambridge/New York, Cambridge University Press 2010.