One the great moral achievements of history is the near-elimination of slavery. In contrast to popular narratives, west and east African kingdoms practiced slavery extensively, both for internal purposes and for external sale to Arabs, who for centuries had transported African slaves to Asia and Europe. East and south Asians had also practiced slavery extensively for millennia. Native Americans also had slaves and other forms of forced labor. How then did humanity evolve to understand that slavery is abhorrent and should be outlawed for the good of humanity. Who if anyone can claim credit for this monumental achievement?