Iron smelting and forging technologies may have existed in West Africa among the Nok culture of Nigeria as early as the sixth century BC.
It had lost its systematic noun-class structure that was present in earlier ancestors, and preserved in distant relatives like Proto-Bantu, but remnants of the system can still be seen.
[5] The Proto-Yoruboid homeland was likely the region of the confluence of the Niger and Benue rivers in what is now Southern Nigeria, where speakers of Yoruboid languages still reside.
[2] While many Yoruboid groups associate the origin of their culture and civilization from the town of Ife, Proto-Yoruboid speakers almost certainly did not live anywhere near modern Ile-Ife.
Controversy exists among linguists on whether Proto-Yoruboid had an expanded nine-vowel system (a, e, ɛ, ɪ, i, ɔ, o, ʊ, u),[clarification needed] with nasal equivalents, retained in some Yoruboid dialects like Ekiti dialect of Yoruba, or rather a seven-vowel system (a, ɛ, e, i, ɔ, o, u), with nasal equivalents, which are seen in most of the descendants of Proto-Yoruboid including Yoruba.
It largely consisted of bisyllabic verbs with vowel roots that served as nominalization prefixes, and may be remnant of a noun class structure found in Volta-Congo.