You don't really need slaves in a hunter and gatherer society (no agriculture, no construction, no mining = no backbreaking work that free people are loath to d

You don't really need slaves in a hunter and gatherer society (no agriculture, no construction, no mining = no backbreaking work that free people are loath to do), and you don't really have the institutions to keep them from running away. As far as our observations of Stone Age people go, if they catch someone, they either kill them or make them a permanent member of the group.