According to several sources, Igbo (also known as Ebo) people evolved over a long period of 4000 BC to 500 AD in Igboland through waves of migrations. There is evidence that the ancestors of Igbo and most of their neighbors were the proto-Kwa group. This ancient group came from the African Great Lakes and Mountains of the moon of East/Central Africa and settled at the old Sahara grasslands. It was the desertification of the Sahara that forced some of the Kwa people to migrate further down to the north of the Niger Benue confluence and founded Nok. Elements of the Kwa people migrated South of the Niger Benue confluence and later became the Igala, Idoma, Yoruba, Igbo, and possibly the Tiv peoples. The Kwa people's first area of settlement in Igboland was the Nsukka-Afikpo-Awka-Orlu uplands over a 5,000 year period. Elements from the Orlu area migrated south, east, and northeast while elements from the Awka area migrated westwards across the Niger river. The Igbo were prized for their knowledge of agricultural tools and crops such as yams, rice and maze.