First, some background. The Indus Valley Civilization was centered on the Indus river and grew and flourished between 3300 B.C.E and 1300 B.C.E. It's exact boundaries are not known, but the sites where the Indus script are found are spread all over Pakistan, Western India, with some additional sites in Oman, Afghanistan and Turkmenistan.
It is considered by most scholars to be one of the major early "primary" states, i.e. it developed independently of influence from the outside. It was an urban civilization, with many large cities, with dense populations, neighborhoods, urban planning, and water and waste management. It also had many smaller towns and villages, mostly agricultural, some engaged in different specialized economic activities, such as coastal fishing villages, and sites with an almost industrial scale of shell bangle production.
So who were the Indus Valley people? Was their script a script or a symbol system?
The article starts off by first quoting a local tour guide saying he's not sure the people of Harappa are his ancestors, because they had such complex technology. Then the article goes on to create a completely false divide between scholars in the west, and scholars in India and Pakistan. According to the author, Andrew Buncombe:
Many experts in south Asia and elsewhere believe that symbols and marks inscribed on seals and other artefacts found here represent an as yet undeciphered language. Arguing it may be the predecessor of one of several contemporary south Asian argots, these experts say it is proof of a literate Indian society that existed more than 4,000 years ago.This ethnic/racial divide between people who claim it is a script and people who claim it isn't is total bull****. Pardon my French. There are plenty of scholars in the "west" who have written extensively about the Indus script as a script - not a symbol system. Examples among these are Asko Parpola - a Finnish professor of Indology at the University of Helsinki, and J. Mark Kenoyer - professor at the University of Wisconsin - Madison (and my academic advisor).
But other experts based in the West say although the symbols may contain information, they are not a true language. They claim the judgement of their counterparts in south Asia may be swayed by regional nationalism.
A variety of people over the years have argued that the Indus script is really a symbol system, and not a real script. Their reasons for this usually stem from the lack of (preserved or discovered) long inscriptions. The vast majority of inscriptions come on Indus seals, with some on pottery, inscribed on shell and terracotta bangles etc. Wherever they are found, they tend to be just 6-10 letters or symbols long. This is the main reason why it has not yet been deciphered. As one of my professors put it, for the Indus Script, all we have is the white pages in the phone book. For those who do believe that these symbols are letters and not pictographs, it is argued that the seals, and other short inscriptions are the names of people and places, probably with honorifics. There may have been inscriptions or texts on paper, bark, papyrus, wood or cloth, all things that are not preserved today. We will probably never know if there were or not.
And that is the real problem with the debate. The answer is we really don't know for sure. We can take the data that we have, and draw inferences and interpretations from it. We know these letters/symbols are standardized, that there are patterns in which ones repeat, and in what order, that they are found on objects that we would consider to most probably have belonged to individuals, and not groups. There is also an inscription, one that was inlaid in wood on a sign board near the gateway to the city of Dholavira. The signboard had fallen, the wood disintegrated over time, but the inlay lay as it had fallen, flat on the ground, buried for thousands of years. We can make an inference, a judgement, based on the context of the inscription, it's placement, location, size etc., that it probably said "Dholavira" or maybe "Welcome to Dholavira". Without decipherment we can't really know for sure.
Aside from the short length of inscriptions, what has prevented any really conclusive and convincing decipherment of the Indus script is the fact that we don't know what languages people were speaking. Note the use of the plural: Languages. That's a huge problem, in a civilization as large and complex as the Indus Valley was, with sites spread across a huge area of mostly Pakistan and India, but also as I mentioned with sites showing presence in Afghanistan, Turkmenistan and Oman, we should not assume that everyone was speaking the same language. They probably were not. There were probably people from diverse backgrounds, speaking different languages, who came to trade, who may have used Indus styles of clothing, ornaments, and other markers of identity (or not), but still spoken different languages, perhaps their "mother-tongue" as well as whatever language was the lingua franca of the Indus Valley, the language people had in common.
It is really only modern identity politics that makes the language question matter. Modern South Asia has hundreds of languages, and most people speak more than one. Battles for identity are fought over language today, and the supposed "Aryan Invasion" that brought Indo-European languages to the subcontinent is an ancient sort of incarnation of the concept that people with a different language and identity came to India and took over. The Aryan Invasion Theory has been thoroughly debunked, but the modern implications of who the Indus Valley people were, are still at issue.
The people of modern Pakistan (and India) should be able to claim that the inhabitants of these amazing sites, with all their amazing technological achievements, are their direct ancestors. That this heritage is their heritage, and not somebody else's . So when someone comes along claiming that the Indus Valley script isn't a script, or that it was used to write a Dravidian-family language instead of an Indo-European one, or some other lost language, it is an insult to the people of modern India and Pakistan.
Because the inscriptions are so short, and because they were most likely using the script to write in more than one language, (the same way the roman script - that I'm using now can be used to write French and Spanish and Italian, among others) we can't really say for sure.
The argument that their civilization was complex, and therefore they must have had writing, is sort of a fallacy, though I can see why people would use it. There is no reason necessarily that a complex society must have had a complex writing system. It just so happens that, as far as we can tell, the Indus script has all the features of a writing system, and not a pictographic or symbol system. The same debate was waged about Egyptian hieroglyphics until the Rosetta Stone was discovered, which allowed the decipherment of hieroglyphics as a script, and not a bunch of symbols (bird, wheat, pot, man, fish, are all letters representing sounds like an alphabet, not symbolic representations of birds, wheat, pots, men, or fish).
So the truth is, we can't really be sure. The Indus script displays all the features of a writing system, (Steven Farmer is really, really wrong about this), but we won't know for sure until it's deciphered, and we can't decipher it until we know what languages they were writing, and which language was being written in a particular inscription. We probably can't know most of those things, unless we find longer inscriptions, or the Indus Valley equivalent of the Rosetta Stone.
Parpola (the Finnish Indologist) and Iravatham Mahadevan (an Indian epigraphist) have both argued that the script was used to write a Dravidian language. Neither of them have yet come up with a conclusive decipherment, but even if they (or someone else) someday is able to prove that the Indus Script was used to write a Dravidian language, this does not mean that the people of the Indus Valley are not the ancestors of modern Pakistan and India, who speak Indo-European languages.
Language and identity are one thing, and genetics another. A good example of this is the diversity of languages that was spoken in France before the standardization of Modern French. The people are the same, but over a number of generations they stopped speaking the languages they used to speak, and started speaking standard French. People may have spoken a Dravidian language (or another language which is lost today), but that doesn't change the fact that there is strong genetic continuity between the people of the Indus Valley Civilization and the modern inhabitants of Pakistan and Northwestern India.
Disclaimer: I'm not a specialist in Indus Valley archaeology. But I am an archaeologist and I have read a lot about this topic. This is my commentary on the subject, not an academic paper -- I'm not citing every statement I make. I probably should, but I don't have time. If you're really interested you can go track down publications by J. Mark Kenoyer, Gregory Possehl, Rita Wright, and many more. For more information check out Harappa.com.
Recently The Hindu newspaper published an interview with Asko Parpola. This is some of what he had to say:
The Hindu: There is some criticism that the Indus script is not a writing system.
Parpola: I do not agree [with that]. All those features of the Indus script which have been mentioned as proof for its not being a writing system, characterise also the Egyptian hieroglyphic script during its first 600 years of existence. For detailed counterarguments, see my papers at the website www.harappa.com.
The Hindu: If it is a writing system, what reasons do you adduce for it?
Parpola: The script is highly standardised; the signs are as a rule written in regular lines; there are hundreds of sign sequences which recur in the same order, often at many different sites; the preserved texts are mostly seal stones, and seals in other cultures usually have writing recording the name or title of the seal owner; and the Indus people were acquainted with cuneiform writing through their trade contacts with Mesopotamia.