Question: Trade beads (sometimes called aggry and slave beads) were otherwise decorative glass beads used between the 16th and 20th century as a token money to exchange for goods, services and slaves (hence the name), this included the African slave trade, slavery has existed in Africa for how long?
Sentence (from "Slavery in Africa"): Slavery has existed in Africa for many centuries, and still continues in the current day in some countries.
Relevant evidence: Yes