Bhutan's early history is shrouded in the mists of Buddhist tradition and mythology. As most important events of the period involved saints and religious leaders, they were therefore chronicled only in scriptures. Unfortunately, due to natural calamities like earthquake and fire, most of these original documents were destroyed and much of this early history relies on reports from British explorers, and on legend and folklore. Archaeological evidence suggests Bhutan was inhabited as early as 1500 BC or possibly even 2000 BC. These early inhabitants were followers of Bon, an animistic tradition that was the main religion of the Himalayan region before the advent of Buddhism.