The Sultanate of Oman is bordered by Yemen, Saudi Arabia, the United Arab Emirates, the Arabian Sea, and the Gulf of Oman. It occupies the southeastern corner of the Arabian Peninsula. Cultural and trade ties of societies in this area to ancient Mesopotamia have been traced back as far as the third or fourth millennium BC. The early social structure of Oman consisted of a number of tribal groups. In the seventh century AD, the Omanis were converted to Islam and most eventually embraced the variation of the religion known as Ibadism. Oman was the center of a far-flung commercial and political empire for many centuries. The current ruling dynasty in Oman—the Al Bu Saids—have been in power since 1749. The Sultanate is comprised almost entirely of Arabs, with small groups of Baluchis, South Asians, and Africans. Despite its rich cultural heritage, Oman was primarily a poor country until the discovery of oil in the 1960s, and it still has a modest per capita income. In spite of its rapid modernization, however, Oman maintains a largely traditional society in accordance with conservative Islamic values.