section_path: History/4th millenium BC – 6th century AD/West Africa
section_name: West Africa
paragraph_text: West Africa
  
  In the western Sahel the rise of settled communities occurred largely as a result of the domestication of millet and of sorghum. Archaeology points to sizable urban populations in West Africa beginning in the 4th millennium BC, which had crucially developed iron metallurgy by 1200 BC, in both smelting and forging for tools and weapons. Extensive east-west belts of deserts, grasslands, and forests from north to south were crucial for the moulding of their respective societies and meant that prior to the accession of trans-Saharan trade routes, symbiotic trade relations developed in response to the opportunities afforded by north–south diversity in ecosystems. Various civilisations prospered in this period. From 4000 BC, the Tichitt culture in modern-day Mauritania and Mali was the oldest known complexly organised society in West Africa, with a four tiered hierarchical social structure. Other civilisations include the Kintampo culture from 2500 BC in modern-day Ghana, the Nok culture from 1500 BC in modern-day Nigeria, the Daima culture around Lake Chad from 550 BC, Djenné-Djenno from 250 BC in modern-day Mali, and the Serer civilisation in modern-day Senegal, which built the Senegambian stone circles from the 3rd century BC. There is also detailed record of Igodomigodo, a small kingdom founded presumably in 40 BC, which would later go on to form the Benin Empire.
  
  Towards the end of the 3rd century AD, a wet period in the Sahel created areas for human habitation and exploitation that had not been habitable for the best part of a millennium, with the Kingdom of Wagadu, the local name of the Ghana Empire, rising out of the Tichitt culture, growing wealthy following the introduction of the camel to the western Sahel, revolutionising the trans-Saharan trade that linked their capital and Aoudaghost with Tahert and Sijilmasa in North Africa. Soninke traditions likely contain content from prehistory, mentioning four previous foundings of Wagadu, and holds that the final founding of Wagadu occurred after their first king did a deal with Bida, a serpent deity who was guarding a well, to sacrifice one maiden a year in exchange for assurance regarding plenty of rainfall and gold supply. Wagadu's core traversed modern-day southern Mauritania and western Mali, and Soninke tradition portrays early Ghana as warlike, with horse-mounted warriors key to increasing its territory and population, although details of their expansion are extremely scarce. Wagadu made its profits from maintaining a monopoly on gold heading north and salt heading south, despite not controlling the gold fields themselves, located in the forest regions. It is probable that Wagadu's dominance on trade allowed for the gradual consolidation of many polities into a confederated state, whose composites stood in varying relations to the core, from fully administered to nominal tribute-paying parity. Based on large tumuli scattered across West Africa dating to this period, it has been stipulated that relative to Wagadu, there were further simultaneous and preceding kingdoms that have unfortunately been lost to time.