One chapter in Africa: A Biography of the Continent is about slavery within Africa:
A history of slavery in Africa claims that between 30 and 60 percent of the entire population were slaves during historical times. If this is correct, then the number of people enslaved in Africa far exceeded the number taken from the continent by the slave trade.
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In this part of Africa [Mozambique] famines were frequent and made terrible depredations, but occurred in some areas more than in others, and people from the affected lands would crowd into unaffected areas where food was to be found. They bought food with anything they possessed, including their own freedom, voluntarily making themselves the slaves of those who would give them sustenance. Desperate individuals would even destroy an item of value belonging to a wealthier neighbor, knowing that the punishment for this symbolic act would be enslavement.
This leads Arnold Kling to think about those opting for enslavement:
1. One of the most potent ways to accumulate wealth and power is to have other people work for you. Karl Marx was not wrong on this. It was true in Classical times, it is true for the owners and managers of large firms, and it is true for politicians, for whom all of us labor in order to pay taxes. Indeed, in Unchecked and Unbalanced I offer calculations which suggest that some relatively ordinary politicians have power that is greater than that of leading billionaires.2. The ideal of freedom and equality may be unrealistic, with only rare exceptions. It could be that the most natural human condition is one of dominance and submission. You can start from a different equilibrium, but somehow you end up with a few people in dominant positions and most people submitting, some quite willingly, to domination.
3. Markets can offer freedom and equality when the option for exit is viable. Instead, if I am totally dependent on my employer for a job (that is, my next best alternative is something with a much lower wage rate), then I must behave very submissively toward my employer. How many people are in such a position? Government workers strike me as an obvious example — many of them would be unable to earn as much in the private sector, particularly now. So they would tend to be highly submissive. In fact, nowadays a lot of people would go nearly to the lengths of described in the last sentence quoted above if it would allow them to be employed by (enslaved by?) the government.
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6. Today, we think of Marxists as authoritarian. An alternative view is that at least some Marxists sincerely wanted freedom and equality, but that dominance-submission is such a natural equilibrium that the only way to replace the capitalist version of dominance and submission was with a statist-authoritarian version.7. For libertarians, the outlook is always going to be precarious. It is not just that there are people who desire to enslave others. It may be very natural for most people to opt for enslavement.