Johnny is descended from a woman, Martha, who born in 1612, and who was of African descent. Martha’s daughter, Elizabeth Key (also an ancestor of Johnny), was the first woman of African ancestry to successfully take legal action to free herself from slavery. This happened in 1656. Johnny is descended from Martha twice (on one family tree, she is both one of his eight times great-grandmothers, and one of his nine times great-grandmothers). That would mean that Johnny is of 3/2048 African ancestry.(1)
I think Depp would be perfect for a Shaka Zulu remake.