Pakistan is a country in South Asia that is officially known as the Islamic Republic of Pakistan. With a population of over 212.2 million people, it is the world's fifth most populous nation and home to the world's second-largest Muslim population. Pakistan has an area of 881,913 square kilometers, making it the 33rd largest country in the world. It has a 1,046-kilometer coastline that runs along the Arabian Sea and Gulf of Oman in the south, and is bordered on the east by India, on the west by Afghanistan, on the southwest by Iran, and on the northeast by China. It shares a maritime boundary with Oman and is isolated from Tajikistan by Afghanistan's Wakhan Corridor in the northwest. Pakistan is home to many ancient civilizations, including the 8,500-year-old Neolithic site of Mehrgarh, which is the oldest in South Asia, and the Bronze Age Indus Valley Civilisation, which is the largest of the Old World's civilisations. The Archaemenid Empire, briefly that of Alexander the Great; the Seleucid, Maurya, Kushan, the Gupta; the Umayyad Caliphate in its southern regions, the Ghaznavids, the Delhi Sultanate, the Mughals, the Durrani Empire, the Sikh Empire, East India Company rule, and, most recently, the British Indian Empire from 1858 to 1947, were among the empires and dynasties that ruled Following the Partition of the British Indian Empire, which granted separate statehood to its Muslim-majority regions and was followed by unprecedented displacement and loss of life, Pakistan gained independence in 1947 after the Pakistan Movement, which sought a homeland for the Muslims of British India, and election victories in 1946 by the Muslim League. Pakistan is a country with a diverse ethnic and linguistic population, as well as a diverse geography and wildlife. Pakistan, which was once a British Commonwealth dominion, adopted a constitution in 1956 and became an Islamic republic. After a civil war, East Pakistan seceded in 1971 to form the new country of Bangladesh. Pakistan was governed by a variety of governments over the next four decades, with definitions ranging from civilian to military, democratic to authoritarian, relatively secular to Islamicist. Pakistan introduced a parliamentary structure with periodic elections in 2010, after electing a civilian government in 2008. Pakistan has the world's sixth-largest standing armed forces; it is a nuclear power and a former nuclear-weapons state. It is one of the world's fastest-growing economies, with a strong and rapidly-growing middle class. Since independence, Pakistan's political history has been marked by periods of significant economic and military development, as well as periods of political and economic instability. Poverty, illiteracy, and corruption are among the country's problems. Pakistan is a significant non-NATO partner and a member of the United Nations, the Shanghai Cooperation Organisation, the OIC, the Commonwealth of Nations, the SAARC, and the Islamic Military Counter Terrorism Coalition.