Slavery existed in Africa before the arrival of Europeans. But slaves in Africa, usually captured in war, were not enslaved for life, and slavery was never hereditary. In some African kingdoms, slaves could marry and own property, including slaves.
By the 16th century, the perceived need for cheap agricultural labor in the Americas led to ever-increasing European involvement in the enslavement of Africans. African tribes engaged in warfare and raids against each other to obtain slaves. African traders marched these kidnapped people to the West coast of Africa where Europeans waited at trading posts to barter for them and in turn sell them for a profit in the Americas.
From the early 1440s, when the Portuguese first traded in human cargo from Africa, until 1888, when slavery ended in Brazil, more than 20 million people were kidnapped in Africa. Between 10 and 15 million of these people survived the forced march to sailing ships and the journey across the Atlantic to enslavement in the Americas. Roughly seven percent, or between 700,000 and 1,050,000, were enslaved in British North America.
The Life and Adventures of Venture
"All the march I had very hard tasks imposed on me, which I must perform on pain of punishment . . . Though I was pretty large and stout of my age, yet these burthens were very grievous to me, being only about six years and an half old." — Broteer describing his enslavement in Africa, c. 1736
Broteer (c. 1729-1805), named Venture Smith by the man who first bought him, was born at Dukandarra in Guinea. Captured in warfare as a child, he was sold into American slavery and purchased his own freedom at the age of 36.
In 1798 the story of his life, as told to schoolteacher Elisha Niles, was published as A Narrative of the Life and Adventures of Venture, a Native of Africa: But Resident above Sixty Years in the United States of America. Related by Himself.
Image and history from Documenting the American South, University of North Carolina