Afghanistan, officially the Islamic Republic of Afghanistan, is a landlocked sovereign state forming part of South Asia, Central Asia, and to some extent Western Asia. It has a population of around 30 million inhabiting an area of approximately 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.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 the Middle Paleolithic. Urban civilization may have begun in the area as early as 3,000 to 2,000 BCE. Sitting at an important geostrategic location that connects the Middle East culture with Central Asia and the Indian subcontinent, the land has been home to various peoples through the ages and witnessed many military campaigns, notably by Alexander the Great, Genghis Khan, and in modern era Western forces. The land also served as a source from which the Greco-Bactrians, Kushans, Hephthalites, Saffarids, Ghaznavids, Ghorids, Khiljis, Timurids, Mughals, Durranis, and others have risen to form major empires.