A bone of prime value

Uh, my name is not Ishango if you thought that's where the URL of this blog came from. I chose it after reading the fascinating story of the Ishango Bone, an ancient bone tool that is believed to be the oldest table of prime numbers. It was discovered in 1950 by Belgian explorer Jean de Heinzelin de Braucourt near the headwaters of the Nile River at Lake Edward (now on the border between modern-day Uganda and Congo). More than 20,000 years old, the Ishango Bone has

...a sharp piece of quartz affixed to one end, perhaps for engraving or writing. It was first thought to be a tally stick, as it has a series of tally marks carved in three columns running the length of the tool, but some scientists have suggested that the groupings of notches indicate a mathematical understanding that goes beyond counting.

Update: An even older object--the Lembombo Bone--was found in Swaziland. This one is actually 10,000 years older than the Ishango bone, and seems to have been the work of an iron ore mining civilization dating back 43,000 years!.