In ancient times, Muslims attacked Aryans in India causing many Aryans to move east into Nepal from what is now west of present Nepal. Slowly they moved west to east as the years passed. Thus, the Aryans came in contact with native tribes (most of Mongolian descent) of modern Nepal. There were 36 tribes at that time, classified as 36 Varnas. Aryans treated the people of the 36 Varnas as Baishyas of their society.