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.
Black history really started in the Americas with slavery. I think that the American people recognized that slavery was a fully American experience and that black Americans are a part of what America is, that the thought that we should have a special month set aside to acknowledge that and to celebrate black Americans' history and contributions to the history of the United States.
This is a very controversial subject. However, most agree that black Americans blame the white for the start of slavery, even with knowing their people sold them, because many whites today still benefit from the damage done due to slavery back then. Many also believe that this generalized blame is because of the fact that because of slavery many white families had more opportunities that have continued to allow them to prosper throughout the years.
Slavery started when Christopher Columbus first came to the Americas. He claimed the land his and enslaved all Native Americans. When Native Americans started to die from the small pox disease, because Christoper Columbus and his crew, they decided to enslaved African Americans and, brought them to the Americas to work because most of them where immune to the disease.
Black slavery started for two primary reasons: (1) Because the African tribes would invade villages and capture whole families and sell them off as slaves to European slave traders for profit and (2) because slaves from other ethnicities would die off shortly after being subject to harsh working conditions.