In his book, The Lost River, Michel Danino wrote the following about the Harappan civilization.
Altogether, the area covered by this civilization was about 800,000 km2 : roughly one-fourth of today’s India, or if we can make comparisons with contemporary civilizations, ancient Egypt and Mesopotamia put together. This vast expanse must have offered unique opportunities as well as posed peculiar challenges — opportunities in terms of a wider choice of sources for raw materials and a richer store of human skill and experience; challenges arising from a greater diversity of regional cultures which had to be integrated , or at least coordinated, and the sheer extent of communication networks required to keep it all together.
It turns out that the Harappans indeed took the challenge seriously and made sure that the script was uniform across this vast region.
“Writing is an important window to the intellectual creativity of a civilisation. Our analysis reveals that people who designed the Indus script were intellectually creative and considerable time and effort went into designing it. The manner in which the signs were modified shows that it was acceptable across all the sites of the civilisation and was not intended for a small group of people,” said Nisha Yadav from TIFR, the principal author of the study.
The Indus script is found on objects such as seals, copper tablets, ivory sticks, bronze implements and pottery from almost all sites of the civilisation. “The Indus civilisation was spread over an area of about a million square kilometres and yet, the sign list over the entire civilisation seems to be the same indicating that the signs, their meaning and their usage were agreed upon by people with large physical separation. A lot of thought, planning and utility issues must have been taken into consideration while designing these signs,” says the TIFR paper, published in the Korean journal, Scripta.
The paper also indicates that the script may have a connection with scripts from India or even China. The authors say that the signs of the Indus script seem to incorporate techniques in their design that were used in several ancient writing systems to make optimum use of a limited number of signs.[Indus script designed with care, say TIFR researchers (via IndiaArchaeology)]