Interesting. I can't say I know Indian history thoroughly, but from what I know India never had slavery like America did. There were other social mechanism that were used to exploit human labor in India though.

can you elaborate on what people you are referring to here when you say they came to India and called themselves Indians.

AFAIK, there is a lot of controversy surrounding the history 'Aryan invasion of India', but I haven't come across any history text that suggests that Aryans turned the natives into slaves.