<P> By far the most exquisite and obscure artifacts unearthed to date are the small, square steatite (soapstone) seals engraved with human or animal motifs . A large number of seals have been found at such sites as Mohenjo - Daro and Harappa . Many bear pictographic inscriptions generally thought to be a form of writing or script . Despite the efforts of philologists from all parts of the world, and despite the use of modern cryptographic analysis, the signs remain undeciphered . It is also unknown if they reflect proto - Dravidian or other non-Vedic language (s). The ascription of Indus Valley Civilization iconography and epigraphy to historically known cultures is extremely problematic, in part due to the rather tenuous archaeological evidence of such claims, as well as the projection of modern South Asian political concerns onto the archaeological record of the area . This is especially evident in the radically varying interpretations of Harappan material culture as seen from both Pakistan - and India - based scholars . In February 2006 a school teacher in the village of Sembian - Kandiyur in Tamil Nadu discovered a stone celt (tool) with an inscription estimated to be up to 3,500 years old . Indian epigraphist Iravatham Mahadevan postulated that the four signs were in the Indus script and called the find "the greatest archaeological discovery of a century in Tamil Nadu". Based on this evidence he goes on to suggest that the language used in the Indus Valley was of Dravidian origin . However, the absence of a Bronze Age in South India, contrasted with the knowledge of bronze making techniques in the Indus Valley cultures, calls into question the validity of this hypothesis . </P> <P> Clay and stone tablets unearthed at Harappa, which were carbon dated 3300--3200 BC., contain trident - shaped and plant - like markings . "It is a big question as to if we can call what we have found true writing, but we have found symbols that have similarities to what became Indus script" said Dr. Richard Meadow of Harvard University, Director of the Harappa Archeological Research Project . This primitive writing is placed slightly earlier than primitive writings of the Sumerians of Mesopotamia, dated c. 3100 BC . These markings have similarities to what later became Indus Script . </P>

Harappa was located on the banks of river