  Archaeological excavations in the sites of the Indus Valley civilization
(2500-1900 BCE) in Pakistan and northwestern India have unearthed a large
number of artifacts with inscriptions made up of hundreds of distinct signs. To
date there is no generally accepted decipherment of these sign sequences and
there have been suggestions that the signs could be non-linguistic. Here we
apply complex network analysis techniques to a database of available Indus
inscriptions, with the aim of detecting patterns indicative of syntactic
organization. Our results show the presence of patterns, e.g., recursive
structures in the segmentation trees of the sequences, that suggest the
existence of a grammar underlying these inscriptions.
