The Tribal People of India were never without religion
The Tribals/Adivasis/Indigenous people of India are/were never Hindus, Muslims, Christians, Budhists..etc. The fundamentalist forces say that they are Hindus by birth which is not true. Because the type of workshop these Tribals do is completely different than the Hindu religion. The Christian Missionaries said that they don't have religion which is not true. They have a peculiar and unique way of worship. They do not have structure form of worship. However, they perform their worship near river or springs, on the top or below the hills, in or near forest by offering water, milk, incenses, flowers, fruits, leaves, roots, crops, cut animals or birds and try to satisfy God/gods/spirits by offering their blood, heads or heats..etc. The government of India calls them as Schedule Tribes and includes them in Hindu population in Census.