Main article: History of the Indian caste system
There is no universally accepted theory about the origin of the Indian caste system. The Indian classes are similar to the ancient Iranian classes ("pistras"), wherein the priests are Brahmins, the warriors are Kshatriya, the merchants are vaishyas and the artisans are shudras.  Varna and Jati
Main articles: Varna in Hinduism and Jāti
According to the ancient Hindu scriptures, there are four "varnas". The Bhagavad Gita says varnas are decided based on Guna and Karma. Manusmriti and some other shastras name four varnas: the Brahmins (teachers, scholars and priests), the Kshatriyas (kings and warriors), the Vaishyas (agriculturists and traders), and Shudras (service providers, laborers). This theoretical system postulated Varna categories as ideals and explained away the reality of thousands of endogamous Jātis actually prevailing in the country as being the result of historical mixing among the "pure" Varnas – Varna Sankara. All those who did not subscribe to the norms of the Hindu society, including foreigners, tribals and nomads, were considered contagious and untouchables. Another group excluded from the main society was called Parjanya or Antyaja. This group of people formerly called "untouchables", the Dalits, was considered either the lowest among the Shudras or outside the Varna system altogether. Several critics of Hinduism state that the caste system is rooted in the varna system mentioned in the ancient Hindu scriptures. However, many groups, such as ISKCON, consider the modern Indian caste system and the varna system two distinct concepts. Many European administrators from the colonial era incorrectly regarded the Manusmriti as the "law book" of the Hindus, and thus concluded that the caste system is a part of Hinduism, an assertion that is now rejected by most scholars[who?], who state that it is a social practice, not a religious belief. Manusmriti was a work of reference for the Brahmins of north India, especially Bengal, and was largely unknown in southern India. Although many Hindu scriptures contain passages that can be interpreted to sanction the caste system, they also contain indications that the caste system is not an essential part of Hinduism. The Vedas placed no importance on the caste system, mentioning caste only once (in the Purush Sukta) out of tens of thousands of verses. Most vedic scholars believe even this to be a subsequent and artificial insertion; B. R. Ambedkar concluded after a thorough study that this is a much later interpolation, giving strong evidence to support his...