I am pain-stricken to say, since the moment I was born, I have found nothing extraordinary in this ancient land of greatness to be exceptionally proud of. I am not a proud Indian. India at its present condition has given me no reason to feel proud.However, I do feel proud of the ancient Indians, just like I feel proud of the ancient Greeks, the Mayans, the ancient Egyptians, the Babylonians and so on. Scientists are beyond borders, just like the ancient scientists of India, whom you prefer to call as sages.
Sometimes, in the ancient writing samples found in the Indian subcontinent, we find that a mixture of Harappan and Brahmi features has been used. This definitely points towards a continuous evolutionary process that transformed the Harappan script into the later day Brahmi. This also explains why many of the Harappan signs seem to have been simply carried forward (even in actual form) in the Brahmi script.
Considering the fact that the Harappan script may have been proto-Brahmi, the underlying language to be expected should be Sanskrit, or proto-Sanskrit, or derivatives of Sanskrit. Many of the rules of evolution that apply to scripts are equivalently true for languages too. Like scripts, languages too render themselves to similar evolutionary inspections, as they too carry imprints of their journey down the ages.