I found this recent series on the BBC very moving.
It featured Samuel L Jackson, an underwater archaelogy team, and some historians shining light on the international slave trade, both here in the UK and in the wider world.
They visited forts on the coast of Africa where slaves were gathered ready for export, and marvelled at the fact that in the centre of the courtyard was a large church.
One story stuck with me, of how the purpose-designed slave ships, carrying men women and children that had been forcibly torn from their homelands, were brought up on deck to excercise. This was not done for humanitarian reasons, but to reduce the numbers who died en route and to make sure that the price they would fetch in the markets they were heading towards was high because they would be in better condition. It was about stock management.
However, it then takes another dark turn. When they were brought on to deck, they were made to dance.

.
Merchandise
.
Once upon a time, people were bought and sold like lawnmowers,
Or second-hand Hondas. Enterprising Christian young men sought their
Fortunes in foreign fields, chasing white ivory or black bodies, both of
Which were worth the trouble because (back then) acquisition
Was a moral imperative. After all, elephants and black people were
Dumb beasts, whose misfortune was to have economic value elsewhere.
It was dirty business, sawing tusks and chaining black children
So small wonder our heroes took carnal comfort between the unwilling
Legs of black women. They were men of science, designing fine ships that ensured
Their valuable assets were always transported efficiently
Every inch stacked and shackled but because our men were not monsters
They knew good management of stock meant value must be preserved and wastage
Minimised so each day the enslaved were pulled out on deck and made to
Dance.