2200 BCE to 200 BCE. Tichitt culture at Dhar Néma, Dhar Tagant, Dhar Tichitt, and Dhar Walata included a four-tiered hierarchal social structure, farming of cereals, metallurgy, numerous funerary tombs, and a rock art tradition. At Dhar Tichitt and Dhar Walata, pearl millet may have also been independently tamed amid the Neolithic. The urban Tichitt Tradition may have been the earliest large-scale, complexly organized society in West Africa, and an early civilization of the Sahara, which may have served as the segue for state formation in West Africa. As areas where the Tichitt cultural tradition were present, Dhar Tichitt and Dhar Walata were occupied more frequently than Dhar Néma. Farming of crops (e.g., millet) may have been a feature of the Tichitt cultural tradition as early as 3rd millennium BCE in Dhar Tichitt. As part a broader trend of iron metallurgy in the West African Sahel in 1st millennium BCE, iron items (350 BCE – 100 CE) were found at Dhar Tagant, iron metalworking and/or items (800 BCE – 400 BCE) were found at Dia Shoma and Walaldé, and iron remnants (760 BCE – 400 BCE) were found at Bou Khzama and Djiganyai. The iron materials found are evidence of metalworking at Dhar Tagant. In the late period of the Tichitt Tradition at Dhar Néma, tamed pearl millet was used to temper the tuyeres of an oval-shaped low shaft iron furnace, one of 16 located on elevated ground. Iron metallurgy may have developed before the second half of 1st millennium BCE, as indicated by pottery dated between 800 BCE and 200 BCE. At Dhar Walata and Dhar Tichitt, copper was also utilized. After its decline in Mauritania, the Tichitt Tradition spread to the Middle Niger region of Mali (e.g., at Méma, Macina, Dia Shoma, and Jenne Jeno), where it developed into and persisted as Faïta Facies ceramics between 1300 and 400 BCE among rammed earth architecture and iron metallurgy (which developed after 900 BCE). Thereafter, the Ghana Empire developed in the 1st millennium CE. Nok culture The Nok peoples and the Gajiganna peoples may have migrated from the Central Sahara, along with pearl millet and pottery, diverged prior to arriving in the northern region of Nigeria, and thus, settled in their respective locations in the region of Gajiganna and Nok. Nok culture may have emerged in 1500 cal BCE and continued to persist until 1 cal BCE. Nok people may