not based on purity-impurity ranking principle, and that the Vedic literature is devoid of the untouchability concept. History Early history and early Vedic period The existence of jati and the precursor of caste has been found in Indus Valley Civilisation (3300 BCE - 1700 BCE). Sociologist S C. Malik writes Indus Valley Civilization saw "perpetuation of caste status by birth" and "caste-class patterns" were found in Indian society since this period. Charles Maisels finds caste stratification to have arisen from occupational groups upon the devolution from urban Indus Valley society. Romila Thapar finds possibility of a caste as pre-Vedic element, and notes that Jati pre-dated Vedic varna. Thapar further notes that Jatis were derived from clans of Indus Valley Civilisation which saw emergence of different occupations that were inherited and became hierarchically organised with unequal access to resources with stringent marriage regulations and rituals becoming rigid system over a period of time. Archaeologist M.K. Dhavalikar has also supported existence of caste system in Indus Valley Civilisation. During the time of the Rigveda (1500 - 1200 BCE), there were two : and . The distinction originally arose from tribal divisions. The Vedic tribes regarded themselves as (the noble ones) and the rival tribes were called dasa, dasyu and pani. The dasas were frequent allies of the Aryan tribes, and they were probably assimilated into the Aryan society, giving rise to a class distinction. Many dasas were, however, in a servile position, giving rise to the eventual meaning of dasa as servant or slave. The Rigvedic society was not distinguished by occupations. Many husbandmen and artisans practised a number of crafts. The chariot-maker () and metal worker () enjoyed positions of importance and no stigma was attached to them. Similar observations hold for carpenters, tanners, weavers and others. Towards the end of the Atharvaveda period, new class distinctions emerged. The erstwhile dasas are renamed Shudras, probably to distinguish them from the new meaning of dasa as slave. The are renamed vis or Vaishya (meaning the members of the tribe) and the new elite classes of Brahmins (priests) and Kshatriyas (warriors) are designated as new varnas. The Shudras were not only the erstwhile dasas but also included the aboriginal tribes that were assimilated into the Aryan society as it expanded into Gangetic settlements. There is no evidence of restrictions regarding food and marriage during the Vedic period. Later Vedic period (1000–600 BCE) In