Human slavery began in prehistoric times.
Originally, it had nothing to do with race: It was a system of using prisoners of war as servants or laborers for those who had captured them. Other slaves were criminals or people who could not pay their debts. Ancient Greeks, Romans, Africans, and Egyptians enslaved whomever they conquered.
In early European cultures, slaves were servants owned by rich people.
In the early 1500s, the Atlantic slave trade began when Spanish and Portuguese ships began transporting African slaves to the West Indies.