I confidently guess that for most of us (reading) the notion of owning of another human being is beyond the pale and monsterous, but obviously a subset of the humans think it the most natural state of affairs and have done so from the very beginning. It is also not a biological phenomena unique to the Human.

It does remain open to debate (or self reflection) to what extent our 'finer' sensibilities are hand-me-downs (per evolving norms) or based on an authentic inner reaction. The problem of historic figures -- men of apparently otherwise good qualities and clearly possessing of good minds -- who apparently did not opt out of slave ownership could suggest that ethics and morality are entirely artificial (i.e. they were intellectual "victims" of their time), but that would seem to be a self-defeating position to take. I personally do not subscribe to a plastic notion of ethics that is merely a product of the times.

I would like to think -- how can I prove it? -- that however tenuous, the rooted-ness of at least some aspects of the mind in the body would necessitate that certain matters in the domain of thought and being, e.g. morality and ethics, be constrained by the 'bias' of the (relatively) static (in evolutionary terms) body. To me that suggests that the fundamental governing thoughts of a thinking species (granting the non-uniqueness of the human mind) can not be purely products of contextual forces. (The most basic form of empathy is mirrored sense response and doesn't really require an advanced cultural or civilizational context to be affective.)

Also note that the notion of 'exploitation' firmly bound with slavery in our modern minds is clearly an orthogonal matter: from ancient times it was understood that the fundamental feature of the relationship concerned the exercise of (free) will. At times and places, the relationship was in fact cast and viewed in a paternalistic light.

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The price is alarming: our value is apparently dropping. (Damn those robots!)

[tongue in vicinity of cheeks, hasn't really committed yet.]

p.s. It would be interesting to hear the thoughts of proponents of strong-AI in this context.

(e.g. an example of the paternalistic approach: http://images.wikia.com/2001/images/0/05/Chandra.jpg )