Does the Ishango Bone Indicate Knowledge of the Base 12? An   Interpretation of a Prehistoric Discovery, the First Mathematical Tool of   Humankind
  In the early fifties, the Belgian Prof. J. de Heinzelin discovered a bone in the region of a fishermen village called Ishango, at one of the farthest sources of the Nile, on the border of Congo and Uganda. The Heinzelin's Ishango bone has notches that seem to form patterns, making it the first tool on which some logic reasoning seems to have been done. In this paper a new interpretation is proposed for these patterned notches, based on a detailed observation of their structure. It can be called the "slide rule"-reading, in contrast to former "arithmetic game" and "calendar" explanations. Additional circumstantial evidences are given to support the hypothesis that the Ishango bone is a primitive mathematical tool using the base 12 and sub-bases 3 and 4. 
Vladimir Pletser
math.HO math.NT