I've read three books on the Bushmen years ago. Their myths/legends suggest that they were more widespread in ancient times and the population presently in Southern Africa is a remnant population.
BTW. The Bushmen are physically different that all other humans on earth. The females have a peculiar 'apron' over the vagina and the males have a perpetual semi erect penis. They also have 'pointy' ears and love to dance around fires all night. They are very shy and never fight...they always run when confronted.(Leprachauns). There are no longer any full blooded Bushmen anymore and have mixed blood with the Bantu.
Then, there are the Irish Fomorians.
"The Fomorians were an ancient sea-faring race it is thought that they originally came from Northern Africa or Asia as they are described as having dark hair and dark skin in the original accounts."
The Fomorians by John Duncan Scottish 19th century artist
IMO, the Fomorians are probably the source of the 'Black Irish.