Untouchablity is also practiced in other religions (especially among the Christians and Muslims in India). Syrian Christains claim to be a superior race and look at other sects of Christianity with contempt. There is no marriage between Syrian Christians and other sects of Christianity. There are even separate burial grounds for "dalit" Christains.
Similarly "Thangals" in Kerala consider themselves as a superior race and will not give their girls to any other sect of Islam in marriage. There are more than 12 castes in Islam in Andhera Pradesh alone.