The subsistence economy of Nubia, like that of Egypt, was wholly agrarian, relying on the never-ending waters of the Nile and the rich black soil deposited along its floodplain. While wheat was the dominant subsistence crop in Egypt, however, the most important crop in Nubia was durra (sorghum), grown in the summer months. In medieval Nubia measures of sorghum were commonly used as media of exchange, in place of currency. Wheat was also grown in the winter months, but was less important. Various vegetables were also raised in "kitchen gardens." Cattle, sheep and goats were all kept, as sources of meat, milk, and wool, but were not of major importance. Dates, grown abundantly throughout the region, were the only significant export crop.
Since in most of Nubia the Nile does not regularly overflow its banks, as it does seasonally in Egypt, all agriculture depends on irrigation. Upstream diversion was possible in the Kerma and Letti basins, but everywhere else lifting devices were required. In early times the only such device available was the shaduf (counter-weighted level-lift), which is capable of irrigating no more than a quarter of a hectare. Around the first century AD, however, the saqia (ox-driven waterwheel) was introduced, resulting in a revolutionary increase in Nubian agricultural productivity. A single saqia, operating throughout the day, is capable of irrigating about two hectares. It became the backbone of all Nubian agriculture, and remained so until near the end of the 20th century, when it finally gave way to diesel pumps.
Agriculture however was not the source of wealth and power for the medieval kingdoms, nor for the Empire of Kush that preceded them. Like all the African civilizations known to history, their wealth derived from the export of uniquely African exotica: ivory, ebony, animal skins, ostrich eggs and feathers, and dark-skinned slaves. Gold, though not exclusive to Nubia, was far more abundant there than in Egypt, and was always an important export commodity. In earlier times all these items could be obtained directly within the territory of Kush, but this was no longer true in the medieval period, when native fauna and flora had retreated southward in the face of advancing desertification. Only gold and slaves could still be obtained within the territories of Makouria and Nobadia; all other items had to be collected upriver. However, the Christian kingdoms sat astride the only secure route - the Nile corridor - through which these goods could reach the Mediterranean lands which so coveted them. The Christian kingdoms profited through the control and taxation of passing trade, as have "middlemen" throughout history.
According to the invaluable tenth-century account of Ibn Selim el-Aswani, Lower Nubia (from the First to the Second Cataract) was a free trade region in which foreign merchants were allowed to travel and to trade without hindrance. Everywhere beyond the Second Cataract, however, foreign trade was a royal monopoly, the cargoes being handed over to royal agents at frontier customs posts either at or just beyond the cataract.
According to Ibn Selim, Egyptian currency circulated in Lower Nubia, but almost no coins have been found archaeologically. It is apparent from a good many documents that measures of grain - chiefly durra - were the primary media of exchange. Silver dirhams (drachmae) are mentioned once or twice in legal documents pertaining to inheritance, but these were evidently items of hoarded wealth, not legal tender.
The chief market for Nubian goods was always Egypt, and the wealth of Nubia therefore waxed or waned in concert with that of the northern country. Egypt in late Roman and Byzantine times was impoverished by excessive taxation, and this is reflected in the relatively impoverished condition of Early Christian Nubian houses and manufactures. The Classic Christian period largely coincided with the Fatimid Caliphate in Egypt (AD 969-1171), a heretical Shiite regime which relied heavily on Nubia both economically and militarily. Not surprisingly, the peak of medieval Nubian prosperity was achieved at this time. The overthrow of the Fatimids in 1171, and even more the establishment of Mamluk rule in 1250, ushered in an era of instability in both Egypt and Nubia, and an inevitable decline in trade and prosperity. In post-Christian times the country became desperately impoverished, though this was due chiefly to the opening of European maritime trade to the West African coasts, ending the age-long importance of the Nile trade route.
Sources: Welsby 2002, 182-215.
(Contributed by William Y. Adams.)