The Ishango bone was initially thought to be 9,000 years old but advanced scientific analysis conducted in a revaluation exercise by researchers revealed that the bone tool was more than 20,000 years old. The Ishango bone is a dark brown length bone tool with a sharp piece of quartz attached to one end. It is believed to have been in use in the Middle Stone Age era.
The archaeological findings were made by Belgian researcher Jean de Heinzelin de Braucourt while on an excavation expedition in the Belgian Congo in 1960. According to African American Registry, the Ishango bone was dug from the Semliki River. The bone was discovered near a fishing community near the headwaters of the Nile River, covered in layers of a volcanic eruption.
The Ishango bone is evidence of how early Africans pioneered basic arithmetic as far back as 25,000 years ago. The Ishango bone was initially assumed to be a tally stick because of the carved three columns found on the length of the bone tool.
Some researchers were of the view that the carvings on the bone tool transcend its purposes for mathematical understanding. The argument is that the three columns in asymmetrical order were built to explain a numeral system.
The central column starts with three notches and then doubles to 6 notches with the process recurring for the number 4, and once again doubling to 8 notches, then reverses for the number 10, which is divided into five. Scientists who have subjected the artefact to thorough analysis say its randomness is for a central purpose that points to multiplication and division by two.
Prehistoric men may have used the Ishango bone for counting and meeting their mathematical needs given the evidence that the numbers on both the left and right columns are all odd numbers. The numbers on the left column are however prime numbers between 10 and 20 with those in the right column comprising 10 + 1, 10 − 1, 20 + 1 and 20 − 1. When one adds up the numbers on each side column they sum up to 60, while the ones in the central column add up to 48.
Author Peter Rudman in his book “How Mathematics Happened: The First 50,000 Years” asserted that the idea of prime could have originated from the concept of division, predating some 10, 000 years, up until 500 years when early men’s understanding of prime numbers deepened.
He said the scientific world has not come up with an explanation on why a tally of something should show multiples of two, prime numbers between 10 and 20 with some numbers that are almost multiples of 10.
Researcher Alexander Marshack, who had researched extensively on the Ishango bone, said the numerals on the bone tool could be an attempt by the early man to track the lunar calendar, though this has been contested by other scientists who argue that the depiction does not back the structure of the calendar.
Another researcher, Claudia Zaslavsky, also argued that the Ishango bone was a creation of a female who sought to calculate her menstrual cycle in connection with the lunar calendar. The Ishango bone has been placed in a public gallery at the Royal Belgian Institute of Natural Sciences, Brussels, Belgium.
The Ishango bone inspired the institution of the National Pi Day which has been celebrated since 1988. It is a marker of the mathematical constant π (pi). The United States House of Representatives In 2009 institutionalized the celebration of Pi Day.