The combination of advanced technology and archaeology has allowed the confirmation that rural areas in sub-Saharan West Africa were connected to intercontinental trade routes at least as far back as the seventh century AD (or CE). It has long been known that major urban centres along the Niger river were linked by trans-Sahara trade caravans to Europe and the Middle East. But now it is clear that rural areas in the region, in what is now Senegal and Mali, peripheral to the Niger river valley, were also connected with this intercontinental trade, via intra-West African routes.

The artefacts, recovered by archaeologists, which allowed this determination, were glass beads. Sixteen such beads were excavated by archaeologists from the University of Geneva (UNIGE) from three rural sites in Mali and Senegal, that dated from the 13^th century AD/CE back to the 7^th century AD/CE. These beads were subjected to laser ablation inductively coupled plasma mass spectrometry, which allowed their chemical composition to be established, without any damage to the beads.

“By analysing the chemical composition of the glass, we can begin to understand the origin of the raw materials used to manufacture it and, in some cases, the period when it was produced,” explained study lead author and UNIGE doctoral student Miriam Truffa Giachet. The main ingredient of glass is silica (a major component of sand), but because its melting temperature is so high (1 713 ˚C), it was mixed with other minerals (referred to as “flux”). The result was that the mixtures, including the silica, melted at a lower temperatures. Then lime (from limestone or from shells) was added to act as a structural stabiliser for the glass.

“It is also important to understand that the production of glass beads involves several stages, generally located in different places,” she pointed out. The raw materials had to be collected, then transported to a primary production centre, where raw glass would be made. The raw glass would then be carried to a secondary production centre, where glass items – such as beads – would be manufactured. These would then be distributed along trade routes. While glass beads might have little value today, that was not the case in pre-modern times.

By cross-referencing the results of the chemical analyses of the beads they had found in Mali and Senegal with data from other archaeological projects and historical sources, the researchers were able to determine that these beads had originated in Egypt, the Levantine coast and the Middle East. They had not originated from the only active African primary glass production centre in that period, which was in what is now Nigeria.

“Trans-Saharan caravans traded horses, guns, luxury objects and salt for ivory, gold and slaves,” cited UNIGE Faculty of Sciences Anthropology Unit researcher Dr Anne Mayor. “The western popular imagination thinks that Africa was disconnected beyond the Sahara, but this was clearly not the case! It was fully integrated into a large international network that linked Africa, Europe and Asia. It was connected to local trade that brought goods of distant origin to the hinterland.”