CAPE COAST, Ghana -- Under the battlements ringing Cape Coast Castle, Britain's former colonial seat in Ghana, a guide showed two dozen schoolgirls the underground passage linking the slave dungeons to the Door of No Return.

Until Britain led the world in outlawing the transatlantic slave trade 200 years ago next month, countless Africans shuffled through here to cramped ships waiting beyond the pounding surf.

But hundreds of Ghanaian girls the same age as those on their school trip to Cape Coast still live in conditions echoing the 18th century plantations in the Americas.

An ancient practice still strong in the country's north and east allows mystic priests to demand virgin brides as servants as atonement from families deemed to have offended ancestral gods...