Ethiopian national identity is grounded in the historic and contemporary roles of Christianity and Islam, and the independence of Ethiopia from foreign rule, stemming from the various ancient Ethiopian kingdoms of antiquity. Some of the oldest skeletal evidence for anatomically modern humans has been found in Ethiopia. It is widely considered as the region from which modern humans first set out for the Middle East and places beyond. According to linguists, the first Afroasiatic-speaking populations settled in the Horn region during the ensuing Neolithic era. Tracing its roots to the second millennium BC, Ethiopia's governmental system was a monarchy for most of its history. Oral literature tells that the monarchy was founded by the Solomonic dynasty of the Queen of Sheba, under its first king, Menelik I. In the first centuries, the Kingdom of Aksum maintained a unified civilization in the region.