relations with 55 countries. While dependent on the Indian military, Bhutan maintains its own military units. The 2008 Constitution established a parliamentary government with an elected National Assembly and a National Council. Bhutan is a founding member of the South Asian Association for Regional Cooperation (SAARC). In 2020, Bhutan ranked third in South Asia after Sri Lanka and the Maldives in the Human Development Index. Bhutan is also a member of the Climate Vulnerable Forum, the Non-Aligned Movement, BIMSTEC, the IMF, the World Bank, UNESCO and the World Health Organization (WHO). Bhutan ranked first in SAARC in economic freedom, ease of doing business, peace and lack of corruption in 2016. Bhutan has one of the largest water reserves for hydropower in the world. Melting glaciers caused by climate change are a growing concern in Bhutan. History Stone tools, weapons, elephants, and remnants of large stone structures provide evidence that Bhutan was inhabited as early as 2000 BC, although there are no existing records from that time. Historians have theorised that the state of Lhomon (literally, "southern darkness"), or Monyul ("Dark Land", a reference to the Monpa, an ethnic group in Bhutan and Arunachal Pradesh, India) may have existed between 500 BC and AD 600. The names Lhomon Tsendenjong (Sandalwood Country), and Lhomon Khashi, or Southern Mon (country of four approaches), have been found in ancient Bhutanese and Tibetan chronicles. Buddhism was first introduced to Bhutan in the 7th century AD. The Tibetan king Songtsän Gampo (reigned 627–649), a Buddhist convert, extended the Tibetan Empire into Sikkim and Bhutan. He ordered the construction of two Buddhist temples, Bumthang in central Bhutan and at Kyichu (near Paro) in the Paro Valley. Buddhism was propagated in earnest in 746 under King Sindhu Rāja (also Künjom; Sendha Gyab; Chakhar Gyalpo), an exiled Indian king who had established a government in Bumthang at Chakhar Gutho Palace. Much of early Bhutanese history is unclear because most of the records were destroyed when fire ravaged the ancient capital, Punakha, in 1827. By the 10th century, Bhutan's political development was heavily influenced by its religious history. Various subsects of Buddhism emerged that were patronised by the various Mongol warlords. Bhutan may have been influenced by the Yuan dynasty with which it shares various cultural and religious similarities. After the decline of the Yuan dynasty in the 14th century, these subsects vied with each other for supremacy in the