This April 1993 edition of “The Digging Stick”, South African archaeology periodical, mulls over the question: did the bushman smoke either tobacco or Dagga before the white man arrived. There is an excellent, if short, section on the history of the Bushmans contact with white homesteaders at the turn of the 19th century. For those of you in the Graaff Reinet area of the Karoo, this will be of interest to you.
Download the pdf here (1.5mb):  Cannabis archeology SA 1812-30