Who were the untouchables in the indian caste system?

Many castes have been called untouchable, which subscribes to the social rule  that commands marriage exclusively within the caste community. Traditionally, the groups characterized as untouchable were people who worked on polluting activities, for example: (1) taking the life of animals for a living, for example, fishermen, (2) killing or disposing of dead cattle for a living, (3) practicing activities that included contact with emissions of the human body, such as feces, urine, sweat, and spittle such as sweepers and washer men, and (4) eating the flesh of cattle or of domestic pigs and chicken, a category into which many  indigenous tribes of India fell.

In general, the name was given to members of low-caste Hindu groups and people outside the caste system. The use of the term and the social disabilities associated with it were declared illegal in India in 1949 and Pakistan in 1953.  

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