The migration that transformed Africa's languages, genes, and cultures

It’s not easy to extract iron from its ore. But the peoples of the ancient city of Great Zimbabwe—the capital of a thriving kingdom in southern Africa between 1000 to 1700 AD—were masters. At sites near the city’s stone ruins, clusters of iron-smelting furnaces survive today as mounds of rubble. At Mashava, a village 25 miles northwest, fragments bear fingermarks of those who long ago smoothed the structures’ clay interiors. Some of the furnaces were nearly an adult’s arm span in width, with walls thick and strong to contain the heat of more than 2,100° Fahrenheit needed to smelt iron. Unlike other furnaces that required workers to force air into them with bellows, these were designed to suck air in, then out through a chimney, no human labor required. This would have made it significantly easier to produce the iron, which was fashioned into hoes, axes, and arrowheads.