In the meantime, among the abolitionists a back-to-Africa movement emerged in the early 1800s. Its advocates accepted the idea advanced by slavery's supporters: that freed slaves would never be able to adapt to white society, and that emancipation would unleash destructive social forces that would tear the country apart. But most of these "reverse colonialists" eventually gave up their idea as unworkable. Not only would returning slaves to Africa be too expensive, and disruptive to the national economy, the slaves themselves had established a culture of their own that was completely foreign to the African continent.

In some regions, such as the string of narrow and lowlying islands off the coast of South Carolina, African culture survived virtually intact, benefiting from slaves' isolation and from the fact that owners were largely absent. But among the majority of slaves, original African culture was gradually, over several generations, replaced...