Sorry. History has been adjusted indicating that ONLY black people were ever enslaved. Supposedly. That neighboring tribes captured and sold them is not relevant. Or something.
Slavery is truly an ancient evil. A great Evil.
Some forms are worse than others, but all versions are evil, including debt slavery.
Yet (even) the BBC says:
The Roots of Slavery The term slave has its origins in the word slav. The slavs, who inhabited a large part of Eastern Europe, were taken as slaves by the Muslims of Spain during the ninth century AD.
the main religious texts of Judaism, Islam and Christianity all recognise slaves as a separate class of people in society. Going back further in time the Mayans and Aztecs kept slaves in the Americas, as did the Sumerians and Babylonians in the Near East. The Egyptians employed huge numbers of slaves, including the Jews, Europeans and Ethiopians.
The Greeks and Romans kept slaves as soldiers, servants, labourers and even civil servants. The Romans captured slaves from what is now Britain, France and Germany. Slave armies were kept by the Ottomans and Egyptians.
In Imperial Russia in the first half of the 19th century one third of the population were serfs, who like slaves in the Americas, had the status of chattels and could be bought and sold. They were finally freed in 1861 by Emperor Alexander II. Four years later slavery was abolished in the southern states of America following southern defeat in the American Civil War.
In Africa there were a number of societies and kingdoms which kept slaves, before there was any regular commercial contact with Europeans, including the Asanti, the Kings of Bonny and Dahomey. http://www.bbc.co.uk/worldservice/africa/features/storyofafrica/9chapter1.shtml