I think the Jungle Book reflects our human nature to ostracize others just because we are different. In Mowgli's Brothers and the story following that, Mowgli was trapped in a sort of social limbo because the wolves excluded him because he was a human, and the villagers excluded him because he was raised by wolves. Also, in the White Seal, The white seal was laughed at because he wanted something more (but in the story he had the last laugh). Overall, I think the story is about social standing, ergo the references to the caste system and also position by birth.
