Relevant obnoxious quote, in a sea of drivel:

  In all these relationships, the structure of obligation is the same. The subject, serf, or slave is obliged to obey the government, lord, or master, and work for the benefit of same. In return, the government, lord or master must care for and guide the subject, serf, or slave. We see these same relationship parameters emerging whether the relationship of domination originates as a hereditary obligation, or as a voluntary obligation, or in a state outside law such as the state of the newly captured prisoner (the traditional origin of slave status in most eras). This is a pretty good clue that this structure is one to which humans are biologically adapted.

  Not all humans are born the same, of course, and the innate character and intelligence of some is more suited to mastery than slavery. For others, it is more suited to slavery. And others still are badly suited to either. These characteristics can be expected to group differently in human populations of different origins. Thus, Spaniards and Englishmen in the Americas in the 17th and earlier centuries, whose sense of political correctness was negligible, found that Africans tended to make good slaves and Indians did not. This broad pattern of observation is most parsimoniously explained by genetic differences.