Editor's note: David Eltis and David Richardson are co-authors of the "Atlas of the Transatlantic Slave Trade." Eltis is Robert W. Woodruff professor of history at Emory University and co-editor of the Transatlantic Slave Trade database. Richardson is the director of the Wilberforce Institute for the Study of Slavery and Emancipation at the University of Hull, England.

Most students of American history understand that a dramatic re-peopling of North and South America began in the years after Christopher Columbus first landed in the New World. But they may not realize that it was Africa, not Europe, that formed the wellspring of this repopulation process.

In the 3¼ centuries between 1492 and about 1820, four enslaved Africans left the Old World for every European. During those years, Africans comprised the largest forced oceanic migration in the history of the world. Who were they? Who organized the slaving voyages? Which parts of Africa did they come from? How did they reach the Americas? And where exactly did they go?

Strikingly, we can now provide better answers to such questions for Africans than we can for European migrants. The African slave trade reduced people to commodities, but commodities generated profits, and where there were profits there was generally good record-keeping. FULL POST