When did black slavery start?

Slavery in general started thousands of years ago, when one group of people captured members of another group of people. The beginnings aren't certain, but it was going on in ancient Egypt, Rome, Greece, Japan, Ancient America... you name it. Slavery in Africa also started thousands of years ago. When one tribe would battle with another, the "loosers" were often captured and forced to work or to be second class "wives" to tribsmen. When the Dutch traders visited Africa seeking something of value to trade, many of the tribes offered captured enemies as a comodity in exchange for the trinkets and other goods offered by the Dutch traders. For many of the slaves, the conditions were better than they would have encountered had they remained the "property" of their enemies in Africa since many of them would have been murdered for their "crime" of being a member of the enemy tribe. That is not to say that there was anything good about slavery. It was a truly evil practice, where one group of people considered themselves to be sufficiently superior to another that they felt the right to "own" a fellow human being. It is generally agreed that the world has become a little more enlightened in the not too distant past, and we have learned to treat even our enemies with enough respect that they are no longer considered slaves.