Potters’ marks and post-firing graffiti on ceramics provide early symbol traditions that some scholars see as precursors to later Indus script sign forms, preceding the Mature Harappan administrative system.
During the Ravi phase at Harappa, a small set of characters are identified as early predecessors to later Indus script signs, suggesting a developmental sequence rather than sudden invention.
In the Kot Diji phase, signs increasingly appear in contexts linked to administration—especially on seals—indicating growing standardization and institutional use before fully mature urbanism.
By about 2600 BCE, the Indus script is considered fully emerged, coinciding with the Mature Harappan period and its intensified use of seals, sealings, and standardized administrative practices.
Mature Harappan administration widely used square stamp seals (often steatite) bearing an animal motif and short Indus inscriptions; these are among the most prominent contexts for the script.
The corpus is characterized by very brief texts—typically 1 to about 20 characters, with an average around five—shaping modern debates about whether the signs encode full language or restricted administrative formulae.
During the Mature Harappan period (commonly framed c. 2600–1900 BCE), signs show notable standardization across a wide geographic area, supporting the view that writing conventions were shared across Indus cities.
Indus-related sealing technologies and stamp seals appear beyond South Asia, including finds in Mesopotamia and the Gulf, consistent with long-distance exchange networks linking the Indus region to West Asia.
The core Mature Harappan horizon is commonly dated to about 2600–1900 BCE; after this, urban systems fragment and the use of classic seal-and-script administration diminishes in the Post-Urban (Late Harappan) period.
Archaeological Survey of India excavations under Daya Ram Sahni began at Harappa in January–February 1921, initiating systematic recovery of Indus material culture including inscribed objects and sealings.
On September 20, 1924, John Marshall published a widely read announcement publicizing the discovery of a “forgotten age,” bringing the Indus civilization and its inscriptions to global scholarly attention.
Iravatham Mahadevan’s The Indus Script: Texts, Concordance and Tables (1977) compiled a large, systematic corpus and sign list, becoming a foundational reference for computational, structural, and comparative studies of the inscriptions.
The Corpus of Indus Seals and Inscriptions Volume 3.1 (2010), edited by Asko Parpola and collaborators, expanded and systematized documentation for major sites (including Mohenjo-daro and Harappa), supporting renewed quantitative and iconographic analysis.
The Indus Script and Harappan Seal Corpus (c. 2600–1900 BCE)
