Despite decades of archaeological research, the origins of iron metallurgy in sub-Saharan Africa remain largely unclear. Yet this technological revolution—crucial for producing efficient agricultural tools—emerged there at least 3,000 years ago. While investigating an archaeological site in eastern Senegal, an international team led by the University of Geneva (UNIGE) uncovered exceptionally well-preserved remains of an ironworking workshop dating back to the 4th century BCE and used for nearly eight centuries. The discovery, published in African Archaeological Review, provides new insights into late prehistoric metallurgical practices in Africa.

In Europe, the Iron Age is generally dated from around 800 BCE to the end of the 1st century CE. However, these chronological frameworks vary widely across different regions of the world. The earliest evidence for iron production is thought to date to the 2nd millennium BCE in Anatolia—modern-day Turkey—and the Caucasus. This technique spread from there to Europe, but did it develop independently in Africa? The question remains open.

Excavations carried out by a team coordinated by UNIGE, in partnership with the Institut Fondamental d’Afrique Noire (IFAN) in Dakar, shed new light new light on the emergence of iron metallurgy in West Africa. At the site of Didé West 1 (DDW1), near the Falémé River valley in eastern Senegal, archaeologists uncovered an exceptionally well-preserved iron-smelting workshop in 2018 that was in use from the 4th century BCE to the 4th century CE. Its longevity is particularly striking, as such sites are typically used for only a few generations.

Well-preserved “tuyères” and bloomery furnaces
The workshop consists of a large heap containing around a hundred tons of slag, a semicircular arrangement of about thirty used “tuyères”—clay pipes that channel air into the furnace—and 35 circular furnace bases, each approximately 30 cm deep. This iron and steel production was likely carried out on a small scale to meet local needs, particularly for the manufacture of agricultural tools.

“Thanks to its exceptional state of preservation, its age, the length of time it remained in use, and its distinctive technical features, this site is truly unique. It offers a rare opportunity to study the continuity and adaptation of an iron smelting technique over the long term,” says Mélissa Morel, postdoctoral researcher at the Laboratory of Archaeology of Africa & Anthropology (ARCAN) within the Biology Section of the Faculty of Science at UNIGE, and lead author of the article.

Documenting practices
Since 2012, the team has been studying both past and present techniques used by potters and blacksmiths in the Falémé Valley. The work of its members has identified several distinct ancient traditions of iron‑ore smelting. At DDW1, the spatial organisation, furnace morphology and associated waste products point to the tradition known as FAL02. It is characterised by small circular furnaces topped with a removable chimney, as well as large clay “tuyères”. A key feature is that these “tuyères” do not have a single air outlet but multiple small openings connected to the main channel by perpendicular side ducts. This design allows air to be distributed to the bottom of the furnace. Another distinctive characteristic is the use of palm nut seeds as packing material at the base of the furnace—a practice not previously documented.

“Despite the very long period during which this workshop operated, this tradition remained remarkably stable, undergoing only minor technical adjustments. This continuity contrasts with other African metallurgical contexts and highlights the importance of understanding the technical and cultural choices made by early metallurgists in iron production,” explains Anne Mayor, director of the ARCAN laboratory in the Biology Section of the Faculty of Science at UNIGE and senior lecturer and researcher at the Global Studies Institute, who led the project.

The team’s research is continuing at other sites in Senegal to compare smelting practices and gain a better understanding of how ironworking techniques developed and spread. To date, only around a dozen sites dating to the first millennium BCE have been well documented and reliably dated across West Africa.