The ancient history of Yemen (South Arabia) is especially important because Yemen is one of the oldest 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 8th century BCE and the 6th century, it was dominated by six main states which rivaled each other, or were allied with each other and controlled the lucrative spice trade: Saba', Ma'īn, Qatabān, Ḥaḑramawt, Awsān, and Himyar. Islam arrived in 630 CE, and Yemen became part of the Muslim realm.