Peter H. Wood explains the advent of race-based American slavery, in an excerpt from his new book on the topic:
By 1650, hereditary enslavement based upon color, not upon religion, was a bitter reality in the older Catholic colonies of the New World. In the Caribbean and Latin America, for well over a century, Spanish and Portuguese colonizers had enslaved “infidels”: first Indians and then Africans. At first, they relied for justification upon the Mediterranean tradition that persons of a different religion, or persons captured in war, could be enslaved for life. But hidden in this idea of slavery was the notion that persons who converted to Christianity should receive their freedom. Wealthy planters in the tropics, afraid that their cheap labor would be taken away from them because of this loophole, changed the reasoning behind their exploitation. Even persons who could prove that they were not captured in war and that they accepted the Catholic faith still could not change their appearance, any more than a leopard can change its spots. So by making color the key factor behind enslavement, dark-skinned people brought from Africa to work in silver mines and on sugar plantations could be exploited for life. Indeed, the servitude could be made hereditary, so enslaved people’s children automatically inherited the same unfree status.
Lifetime servitude could be enforced only by removing the prospect that a person might gain freedom through Christian conversion. One approach was to outlaw this traditional route to freedom. As early as 1664, a Maryland statute specified that Christian baptism could have no effect upon the legal status of a slave. A more sweeping solution, however, involved removing religion altogether as a factor in determining servitude.
Therefore, another fundamental key to the terrible transformation was the shift from changeable spiritual faith to unchangeable physical appearance as a measure of status. Increasingly, the dominant English came to view Africans not as “heathen people” but as “black people.” They began, for the first time, to describe themselves not as Christians but as whites. And they gradually wrote this shift into their colonial laws. Within a generation, the English definition of who could be made a slave had shifted from someone who was not a Christian to someone who was not European in appearance. Indeed, the transition for self-interested Englishmen went further. It was a small but momentous step from saying that black persons could be enslaved to saying that Negroes should be enslaved. One Christian minister was dismayed by this rapid change to slavery based on race: “These two words, Negro and Slave” wrote the Rev. Morgan Godwyn in 1680, are “by custom grown Homogeneous and Convertible”—that is, interchangeable.
Read the whole thing.