In Trinidad and Ghana it is known as susu. In Senegal and Benin these are the tontines. In Nigeria, where it started in the 1700s, it is esusu. Whatever you call it, this system of large-scale pooling of money for mutual benefit shows that Africa has never had a problem with math.
When we learn the history of mathematics, we tend to discover the achievements of the Greek, Hindu, Chinese, and Arab civilizations. If we learn anything about African mathematics, it’s almost entirely about Egypt. But sub-Saharan Africa also has a rich mathematical history – and museums around the world may hold the key to bringing it back to life.
Sub-Saharan Africa has been largely erased from the history of mathematics because many of its traditions were passed down by word of mouth and then lost to disruptive events such as the slave trade. It also suited Europeans to spread the idea that the peoples they captured and enslaved were not significantly intelligent. But the records we have, some written and others linked to historical artifacts that provide insight into everyday life, tell us that complex mathematics has always been at the heart of the activities of African civilizations, just as it has been. always been for civilizations in other parts of the world.
Some of the evidence comes from those who were in contact with slaves and slavers. European captains of slave trading ships, for example, marveled at the mathematical abilities of the African traders they encountered. Sailors who did business with African slave traders described them as “sharp arithmeticians” who could skillfully convert currencies and exchange rates in their heads. According to one account, a broker might have 10 slaves to sell, âand for each of them he demands 10 different items. He immediately reduces them by the head into bars, coppers, ounces, according to the means of exchange which prevails in the part of the country where he resides, and immediately makes the balance â.
This should come as no surprise to us when we look at the numbering system used in the Yoruba language spoken in what is today Nigeria. The expression for “forty-five” translates to “take five and 10 from three twenty”. It may sound bulky, but it is a sign of people comfortable with subtraction and multiplication. The Yoruba started esusu too. Records of pre-colonial Nigeria’s complex financial systems – banks and mutuals, in fact – suggest that managing complicated accounts, loans, credits and debits was just a part of everyday life. They weren’t people who weren’t comfortable with math.
The fact that the instructions for these computing systems were passed by word of mouth makes it all the more impressive, but it also meant that the slave trade decimated their use. We know, for example, that at least one brilliant African arithmetician was enslaved in America. His English first name, after being stolen in Africa at the age of 14, was Thomas Fuller. However, he was also known as the Virginia Calculator due to his extraordinary arithmetic skills. It is impossible to say how many other great mathematical minds have been stolen from Europe, the Caribbean and the Americas, their skills and tutelage lost to those who have been left behind.
It is also impossible to quantify how much these losses impacted the reputation of African mathematics and contributed to 19th and 20th century notions about the intellectual inferiority of the African people. However, we are slowly regaining a better perspective.
Recently, for example, a French researcher showed that the Akan people, who lived in the region we know today as Ghana and CÃ´te d’Ivoire, developed their own numbering system, and did not borrow the Arab and Persian systems as historians had suggested. Jean-Jacques Crappier found proof in the Akan gold weights that were used to weigh gold dust – the dominant currency in the region we know today as Ghana and the Ivory Coast – when exchanges with Arabs, Portuguese, Dutch and English from the 15th to the end of the 19th century.
To carry out the study, which was published last year, Crappier assembled a team of collectors and mathematicians. Between themselves, they determined the masses of as much gold weight as they could get their hands on. The team ended up with records of 9,301 weights from museums and private collections around the world. The distribution of their masses showed that the system was based on the weight of West African seeds, not Arab measures, and they were used in sophisticated ways that helped to convert between the various currencies of the Akan’s trading partners.
It should come as no surprise that complex mathematics was developed and practiced in West Africa. The SankorÃ© University of Timbuktu in Mali was home to many mathematicians, who used their skills in astronomy and accounting. The university became world famous under the 14th century reign of Malian King Mansa Musa, the richest man in the world at the time. Mansa Musa has used his vast gold reserves to attract the best scholars, establish libraries and educate hundreds of thousands of students.
We can see the legacy of centuries of African mathematics in some of the games that are still being played across the continent. One, known by various names such as Ayo, Mankala or Lela, may look a bit like backgammon to Western eyes, but it involves the use of lightning-fast arithmetic skills that have long intimidated casual observers.
There is almost certainly a lot more to highlight. Crappier is now seeking to collaborate with African academics to further explore the implications of his team’s discovery on Akan gold weights, for example. There are many open questions, he says: how did the Akan people develop their sophisticated trading system? How did they make the necessary weights and scales, and how sensitive and precise were they? The answers to these and other questions, which may still be scattered throughout the collections of museums around the world, will surely help us rediscover the awe-inspiring but forgotten truth about African mathematical innovation.
Michael Brooks’ latest book is The Art of More: How Mathematics Created Civilization.