Definition:Ishango Bone

Definition
The Ishango bone is a mathematical tool made from a leg bone of a baboon, dating from approximately $25 \ 000$ years ago.

It bears a system of markings which may be tally marks, but may in fact be for a more complex purpose.

It was found in 1960 by Jean de Heinzelin de Braucourt in the Belgian Congo (now the Democratic Republic of the Congo). It was discovered in the area of Ishango near the Semliki River.

One row of marks contains the prime numbers between $10$ and $20$, that is, $11$, $13$, $17$ and $19$, which total $60$.

Another row contains $9$, $11$, $19$ and $21$, which also total $60$.

The third row contains marks which appear to represent a method of multiplication by means of a technique involving doubling and halving.

While it is suggested that the markings form a calendar, it is also possible that the markings are coincidental, and perhaps just put there to make the bone easier to hold.

Also see

 * Definition:Lebombo Bone
 * Definition:Wolf Bone