This Indus valley civilisation spanned 2,000 sites across 1.5 million square kilometres in the territories of India, Pakistan, and Afghanistan during the Bronze Age (3000-1500 BCE).
Scholars Iravatham Mahadevan and Asko Parpola studied the antiquity of Tamil language and the link between the language and the Indus Valley Civilisation.
Tamil goes back to Proto-Dravidian, can be identified as the language of the thousands of short texts in the Indus script, written in 2600-1700 BCE.
Sanskrit goes back to Proto-Indo-Aryan attested in a few names and words related to the Mitanni kingdom of Syria between 1500 and 1300 BCE.
The earlier forms of Indo-Iranian known only from a few loanwords in Finno-Ugric languages as spoken in central Russia around 2000 BCE.
But none of these very earliest few traces are older than the roots of Tamil.