Cameroon, all of them roughly dating to the sixth century BCE. For the upper Niger River valley in what is now Mali, evidence of iron working dates from the earliest occupation of a major town in the region, Jenne-jeno, in the third century BCE. Especially intriguing is the fact that smelting iron ore and forging it into useful implements and symbols of prestige were being carried out in locations that were some distance from both the ore deposits and the special hardwood trees necessary for making the charcoal that fueled the region’s furnaces and forges. Such a complex spatial organization of the several components of iron production suggests a divided and specialized labor force that, for unknown reasons, had invested in these added costs of transport.7 If and when a bar iron currency was adopted there is not presently known. Similarly, little is known specifically about the subsequent transfers of iron technology to other locales and workers, but it can be inferred that the knowledge and skills traveled local, regional, and interregional trade routes alongside iron products and other goods. As the southerly extension of trans-Saharan trade took on greater significance and intensity after the seventh century CE, it is likely that smelters and smiths would have become more productive and diversified their iron wares with the increasing connections to new markets.
Then, in the second millennium, two gradual historical changes began that reshaped the human geography of West Africa and also the contours of its trading networks. One was a drier climate that prompted large scale southerly demographic movements and concentrations of people in new towns and settlements. The other was an expansion and intensification of Muslim trade across the Sahara, which increased the number of Muslims—both immigrants and local converts—among the populations of sub-Saharan Africa. These economic and cultural transformations led, in turn, to new sources and greater supplies of commodity currencies and more widespread circulation of them.
Climatic change brought transfers of iron technology into new geographical areas and communities. A dry period, lasting from ca. 1100 to ca. 1500, extended the reach of the Sahara’s southern “shore,” driving people southward in search of rainfall adequate for farming. Among them were iron smelters and smiths. By the end of the period, important new iron production centers had arisen in the Futa Jallon massif and the Konyan highlands, both of them mountainous areas that lay on the timber-rich forest edge in the hinterland of the Upper Guinea Coast.8 Even though accessible surface deposits of iron ore were not unusual in West Africa and could be exploited in many locales on small scales, by the sixteenth century these two places in particular became major producers and exporters of bar iron.9
Standard units of bar iron currency usually took the form of semifinished tools or implements that were useful in land clearance, farming, hunting, or war, as well as being widely recognized units of value. Unfortunately, however, there is little to go by in knowing specifically what some of the earliest forms of bar iron were like. They remain obscure because metallic iron tends not to survive in the archaeological record, especially in tropical soils. Examples observed in later times can nonetheless suggest a range of possibilities. André Álvares de Almada, a Luso-African merchant from the Cape Verde Islands who traveled and lived at times on the Upper Guinea Coast in the second half of the sixteenth century, described a form of locally made bar iron being traded up the Gambia River at that time. He took care to note that it was the product of local mining and smelting operations, and he described the physical bars as measuring a hand-span long, three fingers wide at one end, and two fingers wide at the other. Among the dealers in this bar iron, Luso-African merchants were especially keen to have it for their trading voyages to the bays south of the Gambia River around Cacheu and Bissau.10 High demand for bar iron in these latter two locales, together with the description of its form and dimensions, suggest that this particular bar iron unit was a semifinished quantity of the metal based either on agricultural tools, such as a hatchet or hoe blade, or on a personal weapon such as a knife blade.
A later example of bar iron, the famous so-called Kissi pennies of the nineteenth and twentieth centuries, was a much smaller currency form most likely based on a generic arrowhead. These particular units circulated among a number of different language groups in the forest and savanna areas of modern Sierra Leone, northern Liberia, and southern Guinea-Conakry.11 That there were so many specific kinds of useful iron products meant that blacksmiths in different locales had the option of shaping particular bar iron currency units, from small ones to large, both “trademarking” their own products and serving a complex consumer market made up of distinctive and various local needs and preferences.
However, several factors set limits on iron smelting that made it difficult to generate a sustained high-volume production of locally made iron. The hardwood trees preferred for making charcoal fuel became scarce at times through overexploitation, for example, especially in locales where smelters regularly operated large shaft furnaces in smelts that lasted several days or up to a week at a time. Other types of West African smelting furnaces were smaller and so required less charcoal, but they were able to produce only modest amounts of workable iron per smelt. Additional limitations came from the restriction of smelting to the dry season and from the control master smelters exerted over access to iron smelting technology and the specialized skills for carrying it out. Taking these limitations together, it is likely that blacksmiths’ potential demand for supplies of smelted iron and consumers’ demand for their finished iron products were not easily or consistently met. This general fluctuating scarcity helps explain in part why West Africans placed such a relatively high value on iron and why, in turn, European merchants in the era of Atlantic trade encountered such robust markets for their overseas bar iron, especially along the Upper Guinea Coast.
West Africa’s other major historical change between the eleventh and fifteenth centuries—a steady growth in its population of Muslims—led to an increasing influence of Islam in its economies, cultures, and urban life. Al-Bakri, in a manuscript completed in Andalusia in 1068, provided general descriptions of what he called the kingdoms of Gao on the middle Niger River, Takrur in the valley of the Senegal, and Ghana between them on the edge of the desert. He drew his views of these kingdoms from knowledge and direct observations of Muslim travelers and traders as well as from the hearsay they had picked up south of the desert. Taking care to point out the towns in which there were mosques and resident Muslims, he also noted the persistence of polytheistic belief and customs in some locales, including among the leaders of important kingdoms such as Ghana. Other telling details—about the gold trade, the significant numbers of Muslim scholars and legal experts in Ghana, and the prominent positions of Muslims as advisors to its king—would have sent a welcome signal to his readers that their faith was on the rise south of the Sahara.12 And this was indeed the case.
Eighty-six years later the Moroccan geographer al-Idrisi provided valuable additions to what was already known about The Land of the Black People, including news that Ghana’s king was now a practicing Muslim. He also passed on general information about the alluvial goldfields adjacent to the kingdom and the vigorous and lucrative trade in gold northward to the Maghreb, where it was minted into dinar coins. Matters of dress were also of great interest, especially when they indicated that there were peoples south of the Sahara who displayed a Muslim sense of sartorial propriety. Respectable Islamic clothing consisted of waist-wrappers, mantles, tailored shirts, and loose-fitting trousers, made of either local cotton or imported wool or silk.13
Regular extraction of gold from deposits located south of the Sahara helped create an interregional currency zone and an early and important north–south axis of trade out of the goldfields and across the desert to North Africa. Muslim Berber merchants traveling southward from Morocco and Tunisia purchased rock salt that had been mined in Saharan deposits and then cut into standard-sized slabs by slaves from southern non-Muslim regions. They carried their units of rock salt onward to the edge of the desert, where they sold it to specialist long-distance Muslim Juula merchants for an agreed-upon measure of gold. Arabic was the language these merchants had in common, at least for trading purposes. Rock-salt slabs thus entered Juula networks and circulated widely in West Africa as a currency valued either by weight or by linear measure, especially in areas where sea salt was scarce.
The gold dust people exchanged in and around
