I found these drawings by Gustav Fritsch recently while doing some other research. In this paper by Andrew Bank of the University of the Western Cape, we learn that "Fritsch indicated right at the outset of his expedition that his aims were 'ethnographic' and 'anthropological' ... and the collection of a portrait portfolio of 'natives' ('eingeborenen') was the most important aspect of this project". Note that the men and women are drawn with no background or context- this was a deliberate act on the part of Fritsch and other ethnographic portrait artists. Quite a few of these were drawn after photographs, but because of the clunky photographic setup and chairs needed for the subjects, "the background or the context has been painted out of the negative, thus stressing the de-contextualized nature of the subject."
As with all art, they are interesting once you understand the background in which they were made.