The Ishango bone is the oldest attestation of the practice of arithmetic in human history. It was named after the place where it was found in the Democratic Republic of Congo. The Ishango bone is also called a bone tool or the cradle of mathematics. It was found in 1960 and discovered to be about twenty two thousand years old. It is a dark brown bone which happens to be the fibula of a baboon. Connected to this bone was a quartz, which is a mineral crystal, used to engrave.
The Ishango bone carries several incisions organized in groups of three columns. The left column is divided in four groups, with each group possessing 19, 17, 13 and 11 notches. These numbers sum up to 60, but that is not the interesting part. These numbers are the four successive prime numbers between 10 and 20. This constitutes a quad of prime numbers.
The central column is divided into groups of 8. This part of the bone was not very easy to read and therefore some of the groups have a minimum and a maximum number. These numbers are, 7/8, 5/7, 5/9, 10, 8/14, 4/6, 6, 3. The minimal sum of these groups is 48, while the maximal sum is 63.
The right column is divided into 4 groups, where each group has 9, 19, 21 and 11. The sum of these four numbers is 60. The same number as the left column.
At first, the Ishango bone was thought to be just a tally stick with a series of tally marks, but scientists have demonstrated that the groupings of notches on the bone are indicative of a mathematical understanding which goes beyond the simple counting. In fact, many believe that the notches follow a mathematical succession. The notches have been interpreted as a prehistoric calculator, or a lunar calendar, or a prehistoric barcode.
There is a second Ishango bone, but it has not been well studied like the first. There is not much information about this bone apart from that it has 8 groups. The first bone had also been said to track the menstrual cycle of the prehistoric women, but the second bone ruled this out and proved the bones to be a numerical source.
