This photo appears in at least two early 20th century books: Das Weib bei den Naturvolkern : eine Kulturgeschichte der Primitiven Frau by Ferdinand Freiherr von Reitzenstein (c1928), and Woman : an Historical, Gynæcological and Anthropological Compendium by Hermann Heinrich Ploss, Maximilian Bartels,Paul Bartels, and Eric John Dingwall (1935). The second book, by Ploss et al, is based on Das Weib in der Natur- und Völkerkunde : Anthropologische Studien by Dr. H. Ploss (1885), but the photo of the Khoikhoi girls is not in the 1885 book. It should be noted that for all of these books, not all editions have the same photographs.
The first book is in German, and the second is in English. Captions in both German and English identify the girls as “Hottentots”. In researching the background of this photo I read that many today consider the term Hottentot to be derogatory, and prefer the term Khoikhoi. Therefore I used Khoikhoi in the title of this article, but for the sake of historical accuracy I have retained Hottentot in the caption. In America the Khoikhoi would be considered Black, but they are racially distinct from other Black people in Africa.
Ploss et al and the Baron von Reitzenstein both attribute the photograph to Speer. Neither book contains any more information about Speer. Ploss has another photograph from Speer, of the girl on the left in the photo in this article. In that photo the girl is posed to focus attention on her genitals, and I did not think that photo would be acceptable for Pigtails. I do not know if Speer took any more photos in addition to those two. The photos may be from a book by Emil Speer, Zur Erinnerung an meine Dienstzeit beim Pferdedepot Sud S.W. Afrika Weihnachten 1911. Apparently Emil Speer was in the military in what was then German Southwest Africa and could be the Speer who took this photograph. I have not seen the book, so I do not know if it truly is the source of the photos. The homeland of the Khoikhoi includes Namibia, formerly German Southwest Africa.
The photo may be considered an anthropological contrivance, but it is definitely posed for an aesthetic purpose. From what I have seen of books from the early 20th century, nude photographs were more respectable then, and may not have needed a contrivance.