Tribals( Adivasi) people are not Hindus dose not mean that they donot have any religion. You are right Gladson no body has tried to define their religion not even Anthropologists till today. All the anthropologists have defined the tribals from their own perspective.You will not find many Adivasi anthropologist to define or to give " word" to their religion. As adivasis are more dependent on oral tradition many languages and good practises are also not documented properly.
No doubt that some of the adivasis are now worshiping Hindu Gods like "Siba". They do not have the statue like "Siba" but a stone like "Linga".There is need to study who start first worshiping stone and later on may be some stage the word called " Sive" was given to that.No religion is static & you will find some influence of other religion on a particular religion. So also as tribals are living closer to other religion like Hindu they are also practising Hindu festivals in many places. That dose not mean that they are Hindus. Some times I also go to Church & celebrate 25th Dec. that dose not mean that I am Christian where as my religion is Hindu.
This is high time everybody should understand this and work for the Identity & dignity of tribals( Adivasi) of india not part of this or that existing religion.
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