Across the grasslands of West Africa, the epic of Sundiata continues to be told almost eight hundred years after this hero united the kingdoms of the upper Niger River and founded the massive Mali empire. In the Western view, Africa has been a land of primitives who practice the "darkest" of customs, including polygamy, female genital mutilation, cannibalism, ritual murder, incest, witchcraft, and incessant warfare. Some historians claim that Greek civilization actually emerged from African ideas and that nineteenth-century European scholarship tried to hide the debt for racist reasons. With the opening of Europe's Age of Exploration in the mid-1400s, Africans and other non-Europeans fared increasingly badly in European consciousness. Beginning in the 1820s, the American Colonization Society supported a Back-to-Africa movement that attempted to colonize Liberia, on the coast of West Africa, with groups of freed American slaves. By the 1600s, North African pirates were capturing European ships and sailors and not releasing the prisoners until families.