The history of Qatar spans from its first duration of human occupation to its formation as a modern state. Human occupation of Qatar dates back to 50,000 years ago, and Stone Age encampments and tools have been unearthed in the Arabian Peninsula. Mesopotamia was the first civilization to have a presence in the area during the Neolithic period, evidenced by the discovery of potsherds originating from the Ubaid period near coastal encampments. The peninsula fell under the domain of several different empires during its early years of settlement, including the Seleucid, the Parthians and the Sasanians. In 628 AD, the population was introduced to Islam after Muhammad sent an envoy to Munzir ibn Sawa who was the Sasanid governor of Eastern Arabia. It became a pearl trading center by the 8th century. The Abbasid era saw the rise of several settlements. After the Bani Utbah and other Arab tribes conquered Bahrain in 1783, the Al Khalifa imposed their authority over Bahrain and mainland Qatar. Over the following centuries, Qatar was a site of contention between the Wahhabi of Najd and the Al Khalifa. The Ottomans expanded their empire into Eastern Arabia in 1871, withdrawing from the area in 1915 after the beginning of World War I. In 1916, Qatar became a British protectorate and Abdullah Al Thani signed a treaty stipulating that he could only cede territory to the British in return for protection from all aggression by sea and support in case of a land attack. A 1934 treaty granted more extensive protection. In 1935, a 75-year oil concession was granted to QatarEnergy and high-quality oil was discovered in 1940 in Dukhan. During the 1950s and 1960s, increasing oil revenues brought prosperity, rapid immigration, substantial social progress, and the beginnings of the country's modern history. After Britain announced a policy of ending the treaty relationships with the Persian Gulf sheikdoms in 1968, Qatar joined the other eight states then under British protection in a plan to form a federation of Arab emirates. By mid-1971, as the termination date of the British treaty relationship approached, the nine still had not agreed on terms of union. Accordingly, Qatar declared its independence on September 3, 1971. In June 1995, deputy emir Hamad bin Khalifa became the new emir after his father Khalifa bin Hamad in a bloodless coup. The emir permitted more liberal press and municipal elections as a precursor to parliamentary