That a civilization would allow legal space for “cargo of…slaves” is profoundly evil, if only because these people were treated as if they were animals and existed for the benefit of an elite. The Holy Spirit adds the qualifier “that is, human souls” to give expression to the decadence of the elite who bought these slaves (prisoners of war, criminals, or perhaps orphans). In fact, the entire lifestyle of these super rich was built and sustained on the backs of “human souls” who dug the precious metals from the ground, laboured in the fields to grow the crops, managed the camels that carried the goods across land and rowed the boats that carted the goods across water, unloaded the boats, etc.
13 cinnamon, spice, incense, myrrh, frankincense, wine, oil, fine flour, wheat, cattle and sheep, horses and chariots, and slaves, that is, human souls.