<P> The iron industry, in both smelting and forging for tools and weapons, appeared in Sub-Saharan Africa by 1200 BCE, most likely in Egypt . Iron smelting facilities in Niger and Nigeria have been radiocarbon dated to 500 to 1000 BC . The increased use of iron and the spread of ironworking technology led to improved weaponry and enabled farmers to expand agricultural productivity and produce surplus crops, which together supported the growth of urban city - states into empires . </P> <P> By 400 BCE, contact had been made with the Mediterranean civilisations, including that of Carthage, and a regular trade in gold being conducted with the Sahara Berbers, as noted by Herodotus . The trade was fairly small until the camel was introduced, with Mediterranean goods being found in pits as far south as Northern Nigeria . A profitable trade had developed by which West Africans exported gold, cotton cloth, metal ornaments, and leather goods north across the trans - Saharan trade routes, in exchange for copper, horses, salt, textiles, and beads . Later, ivory, slaves, and kola nuts were also traded . </P> <P> In central Nigeria, around 1000 BCE, the Nok culture developed on the Jos Plateau, until it vanished under unknown circumstances by 200 or 300 CE . It was a highly centralised community . The Nok people produced miniature, lifelike representations in terracotta, including human heads, elephants, and other animals . Iron use, in smelting and forging for tools, appears in Nok culture in Africa at least by 550 BC and possibly earlier, prior to 1000 BC . </P> <P> Based on stylistic similarities with the Nok terracottas, the bronze figurines of the Yoruba kingdom of Ife and the Bini kingdom of Benin are now believed to be continuations of the traditions of the earlier Nokite culture . </P>

What impact did trade have on west africa