Discovery of the Indus Valley Civilisation: Part 2
D. Indumathi, The Institute of Mathematical Sciences, Chennai

Recap: The Indus Valley Civilisation was a Bronze Age civilisation in the northwestern regions of South Asia, including parts of north-west India, north-east Afghanistan, and Pakistan (see the map). It lasted for thousands of years, beginning from 3300 BCE (about 5000 years ago), to 1300 BCE, although it had its roots dating back to cultures such as Mehrgarh in 6000 BCE. It was at the peak of its form in the 700 years from 2600 BCE to 1900 BCE, and is considered one of the oldest civilisations (along with ancient Egypt and Mesopotamia) to flourish in Asia. The reason for its vastness is due to its location along the fertile plains of the Indus river, and the seasonal Ghaggar-Hakra river. 
All knowledge of the civilisation was lost, and it was buried deep under the soil, until it was re-discovered, and announced to the world in September, 1924, a hundred years ago. The most famous of its cities that were first excavated were Harappa and Mohenjo Daro (see map). 

The finds
What was actually found in the excavations? Excavations are often called "digs", for obvious reasons. The archaeologist tries to locate a possible site by looking at mounds and doing some shallow digs to see if there is anything buried there. If they think it is a likely site for an ancient city, they spend months and even years at the site, patiently digging down all the layers till they get to the depth they are interested in. For instance, if you dig outside your house, you will only find mainly garbage and maybe some broken toys and household stuff.  This is the most recent layer and tells us about the people who live here today.  Mostly you will find plastic, so maybe some future people will call us the Plastic Civilisation!
As you dig deeper, you uncover older and older cities, and the artefacts from people who lived there long ago. These tell you about their lives and the things they used. The cities of Harappa indicate that they were beautifully planned and built, with bricks that are used even today.
The early Harappan Period goes back 5000 years, to 3,300 BCE. The cities developed along the Ravi river that separates India from Pakistan. People from the mountains slowly moved to settle in the river valleys. The civilisation was already quite well developed, as was its script. In fact, the earliest examples of the Indus script have been dated to the 3rd millennium BCE (3000 BCE).
There is also evidence that the people of this region carried on trade with other cultures that existed at this time. Lapis lazuli and other semi-precious stones were traded for bead-making. Several crops such as peas, sesame seeds, dates and cotton had been domesticated, as also the water buffalo. Isn't it strange to imagine children of those times, eating food similar to what we eat, and running around on fields with familiar crops and animals? I wonder what they would make of our technological side, though.
One thing was also common to those times: by 2,600 BCE, the mature Harappan phase had begun and large urban centres developed. Just as happens today, several people begaqn to migrate from villages to cities, in search of better living conditions. City life was made possible because of the excellent water-management system of the Harappans: they tamed the summer-monsoon flood waters of the Indus river and its tributaries and grew large amounts of food. It is these big cities that have been excavated. Cities such as Harappa, Mohenjo-Daro (in present-day Pakistan) and Dholavira, Kalibangan, Rakhigarhi, Rupar and Lothal (in present-day India). More than 1,000 such sites have been excavated in the last 100 years.
One thing not common to these times: every house had access to water and drainage facilities! Most people who lived in the city were traders or artisans, making seals, beads and other crafts. It appeared to be a prosperous civilisation, with perhaps all members of society being equal, although the extensively well-planned cities indicate that there may have been a central authority to implement this. In addition, unlike similar civilisations, their pottery, seals, weights (used for measuring goods) and bricks were extraordinarily uniform. The weights in particular indicate great accuracy in measuring length, mass and time!  The picture shows some weights which are exhibited in the National Museum in New Delhi today.

Arts and Craft
Both pottery and terracotta have been found, as also a few stone sculptures and even some gold jewllery. Some of the finds that are presently in museums around the world are shown in the pictures. Some toys have also been found. 
Beads and shells were used to make necklaces, bangles, combs. These are used in India even today. Human figures and animals were also found, carved in stone.

Indus Seals
Thousands of seals have been recovered. These were probably used to apply a stamp on goods to prove their authenticity. All the seals are square, about 2-4 cm in length, with a hole at the back to attach a cord. In fact, most of the Indus script that we see are short groups of signs on these seals, and that is why they are so hard to decipher. The seals have images of humans, bulls, human with horns of a bull, and various animal images (see pictures). They have been beautifully carved on soapstone rock. When pressed on some soft material, they will leave the reverse impression on it. You can see some of the Indus scripts on these seals. One of the seals depicting the hump-backed bull is painted on the first page of the Indian Constituion.

The Indus Script
About 500 distinct symbols have been found on stamp seals, pots, and even a signboard that probably hung over a gate of Dholavira. Typically, the inscriptions are short: about 5 symbols/characters in length, with the longest being 34 symbols long (see picture). It is believed that these symbols code for an as-yet unknown language, but it has not been understood and remains one of the greatest mysteries of this civilisation. In fact, the Indus Valley people are known to have traded with Mesopotamians, and seals have been found in Iran, dating back to 2,400 BCE. Usual clues to determine the script are not available. For instance, we do not know the language that they spoke, or even names of any of their rulers or even bilingual announcements in the Indus Valley script along with a translation in a known language (that is what helped decipher Egyptian hieroglyphics). It remains a mystery.
About a 100 years ago, this lost civilisation was found.  It died out by about 1900 BCE, most probably because of a breakdown of urban networks. Change in the rainfall pattern due to failure of the Indian monsoon at that time, led to drought and a decline in trade.  Agriculture suffered because of lack of water, and the residents most likely migrated to the Ganga basin and built smaller villages. Slowly the cities died out. But they have left their evidence, of superbly built and planned cities, and the mystery of their language and the people who inhabited these cities. This story is still awaiting its final ending.
Sources: Several, including Wikipedia, Roja Muthiah Research Library, https://www.harappa.com/museums