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 theorized that the state of "Lhomon" (literally, "southern darkness"), or "Monyul" ("Dark Land", a reference to the Monpa, an ethnic group in Bhutan & Arunachal Pradesh) 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.