The first modern account of the Indus Valley Civilisation came not from a scholar, but from a deserter from the East India Company's army named Charles Masson. In 1829, Masson wandered through the Punjab region, gathering intelligence for the British in exchange for a promise of clemency, and stumbled upon the ruins of Harappa. He made copious notes and illustrations of the site, which he erroneously dated to the time of Alexander the Great's campaigns, yet his discovery marked the beginning of a journey that would eventually reveal a lost civilisation. Two years later, British officer Alexander Burnes visited the same site and noted the baked bricks used in the ancient masonry, but he also observed the haphazard plundering of these bricks by the local population. The bricks were so valuable to the British railway builders that nearly all the track between Multan and Lahore, laid in the mid-1850s, was supported by Harappan bricks, effectively destroying the archaeological record to build the infrastructure of empire. The Archaeological Survey of India was not founded until 1861, and it was not until the 1920s that serious excavations began, led by John Marshall, who declared in 1924 that archaeologists were on the threshold of discovering a long forgotten civilisation. The ruins of Mohenjo-daro and Harappa, now UNESCO World Heritage Sites, stand as silent testaments to a society that thrived from 3300 BCE to 1300 BCE, spanning much of modern-day Pakistan, northwestern India, and northeast Afghanistan. This civilisation was the most widespread of the three early riverine civilisations, alongside ancient Egypt and Mesopotamia, yet its people left behind no grand monuments, no palaces, and no temples, making their story one of the most enigmatic in human history.
Urban Planning and Social Order
The cities of the Indus Valley Civilisation were remarkable for their sophisticated urban planning, which included the world's first known city sanitation systems. Within the cities, individual homes or groups of homes obtained water from wells, and waste water was directed to covered drains that lined the major streets. Houses opened only to inner courtyards and smaller lanes, creating a sense of privacy and security that was unique for the time. The high degree of forward-looking urban planning demonstrates the existence of well-organised local governments capable of formulating and executing a large-scale development program. The cities were divided into two levels from the ground, making one part slightly higher than the other, and were protected by massive walls that likely served as both flood defenses and fortifications. Despite the presence of large public works projects, there is no conclusive evidence of palaces or temples, and the society appears to have been relatively egalitarian. All the houses had access to water and drainage facilities, giving the impression of a society with relatively low wealth concentration. The majority of the cities were constructed in a highly uniform and well-planned grid pattern, and the remarkable consistency of Harappan weights and measures indicates the existence of a central authority able to make definitive regulations. This uniformity extended to pottery styles, ornaments, and stamp seals, leading into the transition to the Mature Harappan phase. The cities of Mohenjo-daro and Harappa very likely grew to contain between 30,000 and 60,000 individuals, and during the civilisation's florescence, the population of the subcontinent grew to between 4 to 6 million people. The vast majority of people lived in rural areas, but the urban centres were hubs of trade, craftsmanship, and administration, connected by an extensive network of rivers and roads.
Copper was abundant at Indus sites, and the people of the Indus Valley Civilisation achieved great accuracy in measuring length, mass, and time. They were among the first to develop a system of uniform weights and measures, with the smallest division marked on an ivory scale found in Lothal in Gujarat being approximately 1.704 mm, the smallest division ever recorded on a scale of the Bronze Age. Harappan engineers followed the decimal division of measurement for all practical purposes, including the measurement of mass as revealed by their hexahedron weights. These chert weights were in a ratio of 5:2:1, with weights of 0.05, 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, and 500 units, each unit weighing approximately 28 grams. The production of copper and bronze increased especially starting with the Kot Diji Phase, and the Early Harappan groups were already well acquainted with copper metallurgy. Major copper and copper ore sources used by the Indus Valley Civilisation included Rajasthan, as far as Oman, and Bahrain, with the Aravalli Range in northwestern India being particularly important. A touchstone bearing gold streaks was found in Banawali, which was probably used for testing the purity of gold. Contrary to older ideas of elite control over metal production, recent research indicates that access to copper and bronze was relatively widespread throughout Indus society. The people also made various toys and games, among them cubical dice with one to six holes on the faces, which were found in sites like Mohenjo-daro. The terracotta figurines included cows, bears, monkeys, and dogs, and the animal depicted on a majority of seals at sites of the mature period has not been clearly identified. Some of these crafts are still practised in the subcontinent today, and some make-up and toiletry items that were found in Harappan contexts still have similar counterparts in modern India.
Trade and Maritime Networks
The Indus Valley Civilisation may have had bullock carts identical to those seen throughout South Asia today, as well as boats, and an extensive canal network used for irrigation has been discovered. During the Early Harappan period, similarities in pottery, seals, figurines, and ornaments document intensive caravan trade with Central Asia and the Iranian plateau. An extensive maritime trade network operated between the Harappan and Mesopotamian civilisations as early as the middle Harappan Phase, with much commerce being handled by middlemen merchants from Dilmun, modern Bahrain. Such long-distance sea trade became feasible with the development of plank-built watercraft, equipped with a single central mast supporting a sail of woven rushes or cloth. The distribution of Indus-type artifacts on the Oman peninsula, on Bahrain, and in southern Mesopotamia makes it plausible that a series of maritime stages linked the Indus Valley and the Gulf region. Indus artifacts were also exchanged beyond this core region, eventually reaching as far as the Nile River valley, Anatolia, and the Caucasus. However, the evidence of sea-borne trade involving the Harappan civilisation is not firm, and the published levels of the basin and its entrance relative to the modern sea level seem to argue against the interpretation of the brick basin at Lothal as a dockyard. Studies of tooth enamel from individuals buried at Harappa suggest that some residents had migrated to the city from beyond the Indus Valley, and ancient DNA studies of graves at Bronze Age sites at Gonur Depe, Turkmenistan, and Shahr-e Sukhteh, Iran, have identified 11 individuals of South Asian descent, who are presumed to be of mature Indus Valley origin. The success of Indus trade in Central and Western Asia did not only rely on the dynamic entrepreneurialism of Indus merchants and the exotic commodities they offered, but also on specific products that were proactively designed and manufactured in the Indus Valley to fulfill the particular needs of foreign markets.
The Enigma of the Script
The Harappan language is the unknown language of the Indus Valley Civilisation, and the Harappan script is yet undeciphered, indeed it has not even been demonstrated to be a writing system. Between 400 and as many as 600 distinct Indus symbols have been found on stamp seals, small tablets, ceramic pots, and more than a dozen other materials, including a signboard that apparently once hung over the gate of the inner citadel of the Indus city of Dholavira. Typical Indus inscriptions are around five characters in length, most of which are tiny, and the longest on any single object, inscribed on a copper plate, has a length of 34 symbols. While the Indus Valley Civilisation is generally characterised as a literate society on the evidence of these inscriptions, this description has been challenged by scholars who argue that the Indus system did not encode language, but was instead similar to a variety of non-linguistic sign systems used extensively in the Near East and other societies. The messages on the seals have proved to be too short to be decoded by a computer, and each seal has a distinctive combination of symbols, making it impossible to derive a meaning for the symbols from the images. A 2009 study by P.N. Rao et al. published in Science found that the Indus script's pattern is closer to that of spoken words, supporting the hypothesis that it codes for an as-yet-unknown language, but this finding has been disputed by other scholars. The most recent volume of the Corpus of Indus Seals and Inscriptions republished photos taken in the 1920s and 1930s of hundreds of lost or stolen inscriptions, along with many discovered in the last few decades. The language being yet unattested in readable contemporary sources, hypotheses regarding its nature are based on possible loanwords, the substratum in Vedic Sanskrit, and some terms recorded in Sumerian cuneiform, such as Meluhha. One hypothesis has been suggested that the bearers of the Indus Valley Civilisation corresponded to proto-Dravidians linguistically, and the break-up of proto-Dravidian corresponding to the break-up of the Late Harappan culture.
Religion and Daily Life
The religion and belief system of the Indus Valley people has received considerable attention, especially from the view of identifying precursors to deities and religious practices of Indian religions that later developed in the area. However, due to the sparsity of evidence, which is open to varying interpretations, and the fact that the Indus script remains undeciphered, the conclusions are partly speculative and largely based on a retrospective view from a much later Hindu perspective. One Indus Valley seal shows a seated figure with a horned headdress, possibly tricephalic and possibly ithyphallic, surrounded by animals, which John Marshall identified as an early form of the Hindu god Shiva. The seal has hence come to be known as the Pashupati Seal, after Pashupati, an epithet of Shiva, but many critics and even supporters have raised several objections to this interpretation. The Great Bath at Mohenjo-daro is widely thought to have been used as a place for ritual purification, and the funerary practices of the Harappan civilisation are marked by fractional burial, in which the body is reduced to skeletal remains by exposure to the elements before final interment, and even cremation. The people of the Indus Valley Civilisation had a diet dominated by meats of animals such as cattle, buffalo, goat, pig, and chicken, and remnants of dairy products were also discovered. Seven food-balls, or laddus, were found in intact form, along with two figurines of bulls and a hand-held copper adze, during excavations in 2017 from western Rajasthan, dated to about 2600 BCE. The dietary pattern remained the same throughout the decline, and the people used complex multi-cropping strategies across both seasons, growing foods during summer and winter, which required different watering regimes. Research confirms that Indus populations were the earliest people to use complex multi-cropping strategies, and there is evidence for an entirely separate domestication process of rice in ancient South Asia.
The Great Collapse
Around 1900 BCE, signs of a gradual decline began to emerge, and by around 1700 BCE, most of the cities had been abandoned. Examination of human skeletons from the site of Harappa in the 2010s demonstrated that the end of the Indus civilisation saw an increase in inter-personal violence and in infectious diseases like leprosy and tuberculosis. The climate change which caused the collapse of the Indus Valley Civilisation was possibly due to an abrupt and critical mega-drought and cooling 4,200 years ago, which marks the onset of the Meghalayan Age. The Ghaggar-Hakra system was rain-fed, and water-supply depended on the monsoons. The Indus Valley climate grew significantly cooler and drier from about 1800 BCE, linked to a general weakening of the monsoon at that time. The Indian monsoon declined and aridity increased, with the Ghaggar-Hakra retracting its reach towards the foothills of the Himalaya, leading to erratic and less extensive floods that made inundation agriculture less sustainable. Aridification reduced the water supply enough to cause the civilisation's demise, and scatter its population eastward. The residents then migrated towards the Ganges basin in the east, where they established smaller villages and isolated farms. The small surplus produced in these small communities did not allow the development of trade, and the cities died out. During the period of approximately 1900 to 1700 BCE, multiple regional cultures emerged within the area of the Indus civilisation, and the largest Late Harappan sites are Kudwala in Cholistan in Punjab, Bet Dwarka in Gujarat, and Daimabad in Maharashtra. The pottery of the Late Harappan period is described as showing some continuity with mature Harappan pottery traditions, but also distinctive differences, and many sites continued to be occupied for some centuries, although their urban features declined and disappeared. Formerly typical artifacts such as stone weights and female figurines became rare, and there was also a decline in long-distance trade, although the local cultures show new innovations in faience and glass making, and carving of stone beads.
Legacy and Continuity
Archaeological excavations indicate that the decline of Harappa drove people eastward, and after 1900 BCE, the number of sites in today's India increased from 218 to 853. Excavations along the Gangetic plain show that cities began to arise there starting about 1200 BCE, just a few centuries after Harappa was deserted and much earlier than once suspected. There was a continuous series of cultural development, and the subsequent material culture was typically characterised by temporary occupation, the campsites of a population which was nomadic and mainly pastoralist, and which used crude handmade pottery. However, there is greater continuity and overlap between Late Harappan and subsequent cultural phases at sites in Punjab, Haryana, and western Uttar Pradesh, primarily small rural settlements. The Aryan migration theory, proposed by Sir Mortimer Wheeler in 1953, suggested that the invasion of an Indo-European tribe from Central Asia caused the decline of the Indus civilisation, but scholars soon started to reject Wheeler's theory, since the skeletons belonged to a period after the city's abandonment and none were found near the citadel. Subsequent examinations of the skeletons by Kenneth Kennedy in 1994 showed that the marks on the skulls were caused by erosion, and not by violence. The Cemetery H culture, the late Harappan phase in the Punjab region, saw some of the designs painted on the funerary urns interpreted through the lens of Vedic literature, but the archaeological evidence does not support the hypothesis that the Cemetery H people were the destroyers of the Harappan cities. The legacy of the Indus Valley Civilisation lives on in the continuity of cultural practices, the development of urban planning, and the enduring mystery of its undeciphered script, which continues to challenge historians and archaeologists to this day.