Afghanistan ⁱ/æfˈɡænɨstæn/ (Persian/Pashto: افغانستان, Afġānistān), officially the Islamic Republic of Afghanistan, is a landlocked sovereign state located in the centre of Asia, forming part of South Asia and Central Asia. With an estimated population of about 29 million, it has an area of 647,500 km² (250,001 sq mi), making it the 42nd most populous and 41st largest nation in the world. It is bordered by Pakistan in the south and the east, Iran in the west, Turkmenistan, Uzbekistan and Tajikistan in the north, and China in the far northeast. The territory of Afghanistan has been an ancient focal point of the Silk Road and human migration. Archaeologists have found evidence of human habitation from as far back as 50,000 BC. Urban civilization may have begun in the area as early as 3,000 to 2,000 BC.