I’m tired of explaining ourselves.
Slaves lived longer in the US. In Africa they ate each other.
This comes off as trying to justify slavery and also being a bit lose with the facts. Not everybody in Africa was a slave, not everybody there was a canibal, and there were certainly individuals whose life was cut short by being captured as slave (particularly while in the dingy hold of a slaver ship). While some individuals might have ended up living longer this can hardly be a justification.