Human habitation in Qatar dates back to 50,000 years ago.[40] Settlements and tools dating back to the Stone Age have been unearthed in the peninsula.[40] Mesopotamian artifacts originating from the Ubaid period (c. 6500–3800 BC) have been discovered in abandoned coastal settlements.[41] Al Da'asa, a settlement located on the western coast of Qatar, is the most important Ubaid site in the country and is believed to have accommodated a small seasonal encampment.[42][43] Some historians have theorized that the Sumerians may have originated from this region.[44][45][46] Kassite Babylonian material dating back to the second millennium BC found in Al Khor Islands attests to trade relations between the inhabitants of Qatar and the Kassites in modern-day Bahrain.[47] Among the findings were crushed snail shells and Kassite potsherds.[42] It has been suggested that Qatar is the earliest known site of shellfish dye production, owing to a Kassite purple dye industry which existed on the coast.[41][48] In 224 AD, the Sasanian Empire gained control over the territories surrounding the Persian Gulf.[49] Qatar played a role in the commercial activity of the Sasanids, contributing at least two commodities: precious pearls and purple dye.[50] Under the Sasanid reign, many of the inhabitants in eastern Arabia were introduced to Christianity following the eastward dispersal of the religion by Mesopotamian Christians.[51] Monasteries were constructed and further settlements were founded during this era.[52][53] During the latter part of the Christian era, Qatar comprised a region known as 'Beth Qatraye' (Syriac for "house of the Qataris").[54] The region was not limited to Qatar; it also included Bahrain, Tarout Island, Al-Khatt, and Al-Hasa.[55] In 628, the Islamic prophet Muhammad sent a Muslim envoy to a ruler in eastern Arabia named Munzir ibn Sawa Al-Tamimi and requested that he and his subjects accept Islam. Munzir obliged his request, and accordingly most of the Arab tribes in the region converted to Islam.[56][better source needed] In the middle of the century, the Muslim conquest of Persia resulted in the fall of the Sasanian Empire.[57] Early and late Islamic period (661–1783) Abbasid Caliphate at its greatest extent, c. 850 Qatar was described as a famous horse and camel breeding centre during the Umayyad period.[58] In the 8th century, it started benefiting from its commercially strategic position in the Persian Gulf and went on to become a centre of pearl trading.[59][60] Substantial development in the pearling industry around the Qatari Peninsula occurred during the Abbasid era.[58] Ships voyaging from Basra to India and China would make stops in Qatar's ports during this period. Chinese porcelain, West African coins, and artefacts from Thailand have been discovered in Qatar.[57] Archaeological remains from the 9th century suggest that Qatar's inhabitants used greater wealth to construct higher quality homes and public buildings. Over 100 stone-built houses, two mosques, and an Abbasid fort were constructed in Murwab during this period.[61][62] When the caliphate's prosperity declined in Iraq, so too did it in Qatar.[63] Qatar is mentioned in 13th-century Muslim scholar Yaqut al-Hamawi's book, Mu'jam Al-Buldan, which alludes to the Qataris' fine striped woven cloaks and their skills in improvement and finishing of spears.[64] Much of eastern Arabia was controlled by the Usfurids in 1253, but control of the region was seized by the prince of Ormus in 1320.[65] Qatar's pearls provided the kingdom with one of its main sources of income.[66] In 1515, Manuel I of Portugal vassalised the Kingdom of Ormus. Portugal went on to seize a significant portion of eastern Arabia in 1521.[66][67] In 1550, the inhabitants of Al-Hasa voluntarily submitted to the rule of the Ottomans, preferring them to the Portuguese.[68] Portuguese era (1507–1650) After the fall of the Jabrid Dynasty with the conquest of Bahrain by the Portuguese, the Arabian coast up to Al Hassa came under the rule and influence of the Portuguese empire. Attempts by the Ottomans to dominate the region were eliminated with the reconquest of the castle of Tarout[69] or Al Qatif in 1551. Archaeological finds are still being excavated from one of the Portuguese fortresses that served as a base to dominate the region as Ruwayda.[70] The first representation of Qatar appears on the Portuguese map by Luis Lázaro in 1563, showing the "city of Qatar" as a fortress, possibly referring to the fort of Ruwayda.[71] Having retained a negligible military presence in the area, the Ottomans were expelled by the Bani Khalid tribe and their emirate in 1670.[72] Bahraini and Saudi rule (1783–1868) A 1794 map by Samuel Dunn depicting Catura (at centre) in the Historical region of Bahrain In 1766, members of the Al Khalifa family of the Utub tribal confederation migrated from Kuwait to Zubarah in Qatar.[73][74] By the time of their arrival, the Bani Khalid exercised weak authority over the peninsula, notwithstanding the fact that the largest village was ruled by their distant kin.[75] In 1783, Qatar-based Bani Utbah clans and allied Arab tribes invaded and annexed Bahrain from the Persians. The Al Khalifa imposed their authority over Bahrain and retained their jurisdiction over Zubarah.[73] Following his swearing-in as crown prince of the Wahhabi in 1788, Saud ibn Abd al-Aziz moved to expand Wahhabi territory eastward towards the Persian Gulf and Qatar. After defeating the Bani Khalid in 1795, the Wahhabi were attacked on two fronts. The Ottomans and Egyptians assaulted the western front, while the Al Khalifa in Bahrain and the Omanis launched an attack against the eastern front.[76][77] Upon being made aware of the Egyptian advance on the western frontier in 1811, the Wahhabi amir reduced his garrisons in Bahrain and Zubarah in order to redeploy his troops. Said bin Sultan, ruler of Muscat, capitalised on this opportunity and raided the Wahhabi garrisons on the eastern coast, setting fire to the fort in Zubarah. The Al Khalifa was effectively returned to power thereafter.[77] A partially restored section of the ruined town of Zubarah As punishment for piracy, an East India Company vessel bombarded Doha in 1821, destroying the town and forcing hundreds of residents to flee. In 1825, the House of Thani was established with Sheikh Mohammed bin Thani as the first leader.[78] Although Qatar was considered a dependency of Bahrain, the Al Khalifa faced opposition from the local tribes. In 1867, the Al Khalifa, along with the ruler of Abu Dhabi, sent a massive naval force to Al Wakrah in an effort to crush the Qatari rebels. This resulted in the maritime Qatari–Bahraini War of 1867–68, in which Bahraini and Abu Dhabi forces sacked and looted Doha and Al Wakrah.