The history of Yemen is especially important because Yemen is one of the olest centers of civilization in the Near East. Its relatively fertile land and adequate rainfall in a moister climate helped sustain a stable population, a feature recognized by the ancient Greek geographer Ptolemy, who described Yemen as Eudaimon Arabia (better known in its Latin translation, Arabia Felix) meaning "fortunate Arabia" or Happy Arabia. Between the 12th century BCE and the 6th century CE, it was dominated by six successive civilizations which rivaled each other, or were allied with each other and controlled the lucrative spice trade: M'ain, Qataban, Hadhramaut, Awsan, Saba and Himyarite. Islam arrived in 630 CE, and Yemen became part of the Muslim realm.