Morally slavery was rationalized as both an ancient practice and also one that involved foreigners, criminals, or unfortunate prisoners of war. Skin color was not generally a prerequiste or even crucial factor in who was enslaved. In fact, the majority of slaves in the Roman Empire were whites drawn from the Romans on-going warfare in Europe and the Near East. Interestingly, fair-skinned redheads often brought the highest bids in Roman slave markets.

As already mentioned with Egypt, slavery existed in Africa even back into far ancient times. As with other parts of the world, slaves generally were war captives and their descendents. Except for certain somewhat exceptional periods and places, slavery was not so much an industry as a by-product of warfare. Greek, Roman, and later Rus/Viking slavers did exploit Ukrainian peoples almost solely for slaves. Omani slavers centered in Zanzibar (Tanzania) also developed a slaving network in east Africa by the Middle Ages.

In my geography classes I've had students read articles on slavery such as in a fairly recent edition of National Geographic magazine. This article mentions pre-European slavery in west Africa involving war captives. Ironically, however, students' comment papers sometimes twist this information into comments such as "how awful to learn that black people enslaved their own kind." Such statements are clearly ethnocentric in that these students view all black Africans as one people. Yet, I doubt such students would view Romans from Italy enslaving Gauls from France as an instance of whites Europeans "enslaving their own." The Romans and the Gauls quite certainly did not share the same religion, language, or ethnic identity although today we might view them both as "white" or "European." Similarly, the Fulani and the Ashanti of west Africa did not view each other as the same people.

The 1400s and 1500s witness a growing consolidation of European nation-states and national identities. To the east and south, however, the growing Ottoman Empire poses an economic challenge to Europeans: the Ottomans now control trade along the western terminus of the Silk Road as well as the spice trade from India and Indonesia.

Perhaps most importantly, however, Europeans are craving an ever greater supply of sugar, an agricultural product that over millenia had spread from its native New Guinea to India and eventually via Musliam farmers to North Africa, the Mediterranean, and Spain. With the Ottomans having almost a monopoly on cane sugar in the Mediterranean, Spanish and Portuguese farmers found European markets willing to find a new source of sugar. With the Reconquest, the technology to grow and process sugar passed into the hands of Spanish and Portuguese Christians from the Moors. By the mid-1400s the Spanish and Portuguese are planting sugar cane plantations along suitable areas of the Iberian Peninsula. Eventually they find various Atlantic island chains such as Madeira, the Canaries, the Azores, and such. On the Canary Islands the Spanish encounter the Guanches, a fair-skinned people. The Guanches are enslaved. Sugar cane plantations and a system of oceanic shipping are established to grow, process, and transport sugar to Europe. The Guanches are killed off via harsh slave conditions, hunted down, or die from disease. Eventually the Spanish find replacements by buying west African slaves captured in war or sentenced to slavery for crimes. Thus, the Spanish take advantage of a pre-existing practice of slavery both by enslaving the non-Christian white Guanches and by purchasing non-Christian African peoples from other African nations.

By 1492 a system already exists on Atlantic islands for plantation agriculture, native enslavement/extermination, oceanic shipping, and African slave labor. On his second voyage to the Americas, Christopher Columbus takes sugar cane to the island of Hispaniola, an act that eventually brings to the Caribbean the plantation system described above. Like the Guanches, the original Caribbean Indians (Carib, Arawak, and others) are either killed via harsh slave conditions, reprisals against rebellions to Spanish colonialism, or most commonly, die from Old World diseases against which Native Americans have little or no immunity. As in the Canary Islands, the Spanish then turn to African peoples (who share with Europeans a greater immunity to smallpox, whooping cough, malaria, and other Old World diseases) as replacement slave laborers. This sets in motion the socioeconomic and eventual legal system in which the legal status of Kentuckians of African descent has arisen over the last 500 years of European colonial and subsequently American rule.