Key points are not available for this paper at this time.
Journal Article Journal of the Royal Anthropological Institute Get access Journal of the Royal Anthropological Institute. July to December, 1920. Vol. 50. African Affairs, Volume XX, Issue LXXX, July 1921, Page 314, https://doi.org/10.1093/oxfordjournals.afraf.a101768 Published: 01 July 1921
A 1921 study studied this question.