In 1943, in the central Nigerian town of Jos, British archaeologist Bernard Fagg received a terracotta head that had been on a scarecrow in a nearby field. The piece resembled a terracotta monkey head he had seen a few years earlier, and neither piece matched the artefacts of any known ancient African civilisation.
     Fagg discovered local people had been finding terracottas in odd places for years. He soon gathered nearly 200. Soil analysis dated them to around 500 BCE. This seemed impossible since the type of complex societies that would have produced such works were not supposed to have existed in West Africa that early. But when Fagg subjected plant matter found embedded in the terracotta to the then-new technique of radiocarbon dating, the dates ranged from 440 BCE to 200 CE. He later dated the Jemaa scarecrow head to about 500 BCE using thermo-luminescence, which gauges the time since baked clay was fired. Fagg and his collaborators had apparently discovered a hitherto unknown civilisation, which he named Nok.
     Fagg also unexpectedly found 13 iron furnaces, with terracotta figurines in such close association that he postulated they were objects of worship to aid blacksmithing and smelting. Carbon dating gave the Nok the earliest dates for iron smelting in sub-Saharan Africa up to that time.
     Fagg knew such a society did not appear in isolation. He later wrote that Nok culture had almost certainly begun earlier and survived longer than he had evidence for at the time. Scholars are now finding that Nok may have been the first complex civilisation in West Africa, existing from at least 900 BCE to about 200 CE, and their terracottas have become some of the most iconic ancient objects from Africa.
     Excavators regularly find iron tools only a short distance from Nok stone axes, suggesting they were used in the same communities - maybe even the same households - attesting to the manufacture of iron while stone was still being used.
     Evidence has also reinforced a view held by most archaeologists that ancient West Africans moved from stone tools directly to iron, without an intervening copper age. That's a leap that few other parts of the world appear to have made. With the exception of a site in Mauritania known as Grotte aux Chauves-souris, and another in Niger called Cuivre II, researchers have yet to find evidence of copper smelting before iron smelting anywhere in West Africa.

Edited from Archaeology (July/August 2011)