What is the earliest ancient Indian history which is supported by empirical evidence?

There is a lot of hoopla in India these days about its mythical past. But enough about that. I am interested in learning what are the earliest Indian history that is supported by empirical evidence. I assume that the history which is accepted by all historians. I want to assume that there is no bias or agenda behind the information that I receive. But what sources are there to get this information from?