It's funny (not ha-ha funny) how the desire for unfree labor was undermined by the control of the colonizing states, which had to, by the tenets of their own faith, push a faith which made the enslaved coreligionists. What do you do when you convert all the locals under your authority? Look for a foreign supply of infidels from somewhere that isn't profitable to directly control yet.

Fucking vile.

You can see the last echoes of the pre-racist (or at least pre-modern racist - religious and culturally chauvinist attitudes were rampant, but hereditary/phenotypical disgust was not very strong) attitude in the expedition of Cristóvão da Gama to reinforce the Christian Ethiopians against a Muslim jihad. They were coreligionists, even if of a different sect, so they were 'good'.

I recently learned that racism came after slavery in order to justify treating other people as lesser value. Really opened up my eyes to things.