Science: Africa’s Ancient Steelmakers

The Haya were centuries ahead of European metallurgists

When Anthropologist Peter Schmidt first visited the Haya people of Tanzania on the western shore of Lake Victoria, nine years ago, his goal was to study their complex heritage, which is passed orally from one generation to the next. On that and subsequent trips, he not only accomplished what he had set out to do but made a serendipitous discovery that alters the history of technology.

Writing in the current issue of Science, Schmidt and Metallurgy Professor Donald Avery, both of Brown University, report that as long as 2,000 years ago, the Haya people were producing medium-carbon steel in preheated, forced-draft furnaces. A technology this sophisticated was not developed again until nearly 19 centuries later, when German-born Metallurgist Karl Wilhelm Siemens, who is generally credited with using an open-hearth furnace, produced the first high-grade carbon steel.

Schmidt was led to his discovery by Haya elders, who showed him a “shrine tree” that they said marked the site of ancient iron smelters long worked by their people. Because the Haya can now buy inexpensive, European-made steel tools and make more money raising coffee and other crops, they stopped producing their own steel some 50 years ago. Thus the only Haya who could recall details of the steelmaking process were very old, and as Schmidt and Avery write, this knowledge was “threatened every day by the passage of time, by death and by age-related infirmities occurring in this quickly shrinking group of expert smelters.”

Two years ago, at the request of the scientists and working entirely from memory, the Haya constructed a traditional furnace. It was 1.6 meters (5 ft.) high, cone-shaped, made of slag and mud and built over a pit packed with partially burned swamp grass; these charred reeds provided the carbon that combined with the molten iron ore to produce steel. Eight ceramic blowpipes, or tuyeèo a goatskin bellows outside. Using these pipes to force preheated air into the furnace, which was fueled by charcoal, the Haya were able to achieve temperatures higher than 1800° C (3275° F.), high enough to produce their carbon steel.

Schmidt and Avery, certain that the Haya steelmaking process was very old, set out to trace its origins. What they found was beyond even their expectations. Last year, in excavations on the western shore of Lake Victoria, they discovered the remnants of 13 furnaces nearly identical in design to the one the Haya had built. Using radioactive-carbon dating processes on the charcoal, they found that these furnaces were between 1,500 and 2,000 years old, which proved that the sophisticated steelmaking techniques demonstrated by the contemporary Haya were indeed practiced by their ancestors. This discovery, the scientists conclude, “will help to change scholarly and popular ideas that technological sophistication developed in Europe but not in Africa.” ∎