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", a reference to the indigenous Mon religion), or Monyul ("Dark Land", a reference to the Monpa, the aboriginal peoples of Bhutan) 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.