Ethiopian national identity is grounded in the long history of Christianity and Islam in the region, and independence from foreign rule since 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 of Africa region during the ensuing Neolithic era. Tracing its roots to the second millennium BC, the governmental system of Ethiopia was a monarchy for most of its history. Oral literature narrates the foundation of monarchy by King Solomon and Queen of Sheba, via its first king, Menelik I. The Kingdom of Aksum maintained a unified civilization in the region from the 1st century AD until its fall in the 10th century where "Ethiopians" was first coined during Ezana's reign in the 4th-century. The short-lived Agaw-ruled Zagwe dynasty lasted over three centuries until the last king was overthrown by the Abyssinian nobleman Yekuno Amlak. In 1270, he established the Ethiopian Empire, asserting its dynasty lineage from King Solomon and Queen of Sheba. In the Middle Ages, the empire began extending its territory southward, seizing several kingdoms of southwestern region, albeit challenged by Muslim polities such as the Sultanate of Ifat and its successor, the Adal Sultanate. This culminated in the Ethiopian–Adal war, in which Adal and its allies conquered much of Ethiopia. By the mid-16th century, with the help of Portugal, Ethiopia reconquered its territory. In mid-18th century, Ethiopia experienced decentralization known as ''Zemene Mesafint''– regional lords mostly from Oromo and Tigray tribes partitioned into autonomy. Tewodros II managed to reinstate the empire in 1855, inaugurating modernization.