The Atlantic slave trade was the largest forced migration in human history. Between approximately 1500 and 1900, an estimated 12.5 million people were forcibly removed from Africa and transported across the Atlantic as enslaved cargo. Approximately 1.8 million died during the Middle Passage — the transatlantic voyage from Africa to the Americas — from disease, violence, suicide and the physical conditions of the transport. The remainder were sold into plantation slavery in the colonies of the European powers and their successor states in the Americas.

The slave trade was not a lawless enterprise conducted in defiance of legal norms. It was a legally organized, contractually structured, commercially regulated system that operated within the framework of the maritime law this series has been tracing from Babylon through Rome through the Papal Bulls. The same legal concepts that governed the transport of goods governed the transport of enslaved human beings. Ships’ captains were legally defined as merchants transporting cargo. Enslaved Africans were legally defined as cargo. The insurance contracts that covered slave ships covered the cargo — which meant they covered the enslaved people as property. When 132 enslaved Africans were thrown overboard from the slave ship Zong in 1781, the owners filed an insurance claim for the loss of their cargo. The case went to court. The court initially found for the owners. The question was not whether throwing human beings overboard was murder. The question was whether it was a valid exercise of the maritime law doctrine of jettison — the deliberate throwing overboard of cargo to save a ship.

The Asiento — The Legal Contract of the Slave Trade

The Asiento was a contract, issued by the Spanish Crown, granting to designated parties the exclusive right to supply enslaved Africans to the Spanish colonies in the Americas. The Asiento was one of the most commercially valuable contracts in the history of European colonialism. The right to supply enslaved Africans to Spain’s American colonies was worth enormous sums, and the Asiento was fought over by the European powers with the same intensity that any other monopoly commercial right would be contested.

The Asiento demonstrates, with the clarity that legal documentation provides, the complete integration of the slave trade into the legal and commercial framework of European colonial capitalism. The slave trade was not conducted in the shadows or against the law. It was conducted under contract, regulated by commercial law, organized through the financial instruments of early capitalism, and protected by the same legal systems that protected any other form of property and commercial enterprise. Understanding this is essential to understanding how the profits of the slave trade were accumulated, invested and transmitted through the legal instruments of property, inheritance and corporate organization into the contemporary wealth of the families and institutions that benefited from it.