1
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.Subhajit Ganguly
2
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.Subhajit Ganguly