Changes

Perhaps the core common patterns of slavery through different periods is economic disparity between those who enslave and slaves. Slavery has also been an expression of power by individuals and societies seeking to subjugate other people. At times, slavery may have served as a type of punishment system, more similar to our penal systems of today. Relative to the history of slavery, race-based slavery has only occurred in limited periods and the origins of that were economic and expressions of power over vulnerable people. We don't know if slavery developed in periods where written sources were not available. Slavery could have been an expression of humanity's human desire to dominate others or it may reflect economic disparities that emerged as resources were accumulated with the rise of social inequality.