Forgotten history prior to its rediscovery in the 1920s, the Indus Civilization ranks with its contemporaries, Mesopotamia and Ancient Egypt, as one of the three earliest civilizations, displaying planned cities, agriculture, writing, architecture, etc.

The Indus Civilization was not the earliest civilization; Mesopotamia and Ancient Egypt both developed cities slightly before the Indus Civilization did. Nevertheless, the Indus Civilization was by far the most geographically extensive. To date, 1052 settlements have been found. Over 140 of these sites lie along the seasonal Ghaggar-Hakra river. This system was once permanent and flowed as far as Derawar where it ended in an inland river delta. This area was the primary food producing region of the Indus Civilization.

Other Indus civilization settlements were situated along the Indus and its tributaries or spread as widely as Mumbai (Bombay) to the south, east of Delhi, the Iranian border to the west and the Himalayas to the north. Among the settlements are numerous cities, including Dholavira, Ganweriwala, Harappa, Lothal, Mohenjo-daro and Rakhigarhi. At its peak, its population may have exceeded five million people.

For all its achievements, the Indus civilization is still poorly understood. Its very existence was forgotten until the 20th century. Its writing system, Indus script, remains undeciphered, and it is not known whether it gave birth to the later Brahmi script. Currently this is thought to be unlikely. Among the Indus civilization's mysteries are fundamental questions, including its means of subsistence and the causes of its sudden disappearance, beginning around 1900 BC. We do not know what language Indus civilization spoke. We do not know what they called themselves. All of these facts stand in stark contrast to what is known about its contemporaries, Mesopotamia and ancient Egypt.

Predecessors

The Indus civilization was predated by the first farming cultures in south Asia, which emerged in the hills of Balochistan, Pakistan, to the west of the Indus Valley. The best-known site of this culture is Mehrgarh, established around 6500 BC. These early farmers domesticated wheat and a variety of animals, including cattle. Pottery was in use by around 5500 BC. The Indus civilization grew out of this culture's technological base, as well as its geographic expansion into the alluvial plains of what are now the provinces of Sindh and Punjab in contemporary Pakistan.

By 4000 BC, a distinctive, regional culture, called pre-Harappan, had emerged in this area. (It is called pre-Harappan because remains of this widespread culture are found in the early strata of Indus civilization cities.) Trade networks linked this culture with related regional cultures and distant sources of raw materials, including lapis lazuli and other materials for bead-making. Villagers had, by this time, domesticated numerous crops, including peas, sesame seed, dates, and cotton, as well as a wide range of domestic animals, including the water buffalo, an animal that remains essential to intensive agricultural production throughout Asia today.

Emergence of civilization

By 2600 BC, some pre-Harappan settlements grew into cities containing thousands of people who were not primarily engaged in agriculture. Subsequently, a unified culture emerged throughout the area, bringing into conformity settlements that were separated by as much as 1,000 km. and muting regional differences. So sudden was this culture's emergence that early scholars thought that it must have resulted from external conquest or migration. Yet archaeologists have demonstrated that this culture did, in fact, arise from its pre-Harappan predecessor. The culture's sudden appearance appears to have been the result of planned, deliberate effort. For example, some settlements appear to have been deliberately rearranged to conform to a conscious, well-developed plan. For this reason, the Indus civilization is recognized to be the first to develop urban planning.

Cities

The Indus civilization's penchant for urban planning is evident in the larger settlements and cities. Typically, the city is divided into two sections. The first area includes a raised, earthen platform (dubbed the "Citadel" by early archaeologists). The second area (called the "lower city") contains tightly packed homes and shops, as well as well-defined streets that were laid out to a precise plan. A system of uniform weights and measures was in use, and streets and alleys are of rigidly uniform width in virtually all Harappan sites. The main building material was brick, both fired and sun-baked, of a rigorously standardized shape. The largest cities contained as many as 30,000 people.

As seen in Harappa, Mohenjo-daro and the recently discovered Rakhigarhi (the best-known and possibly the largest cities), this urban plan included the world's first urban sanitation systems. Within the city, individual homes or groups of homes obtained water from wells. From a room that appears to have been set aside for bathing, waste water was directed to covered drains, which lined the major streets. Although the well-engineered system drained waste water from the city, it seems clear that the streets were far from fragrant. Houses opened only to inner courtyards and smaller lanes.

The purpose of the "Citadel" remains a matter of debate. In sharp contrast to this civilization's contemporaries, Mesopotamia and ancient Egypt, no large, monumental structures were built. There is no conclusive evidence of palaces or temples — or, indeed, of kings, armies, or priests. Some structures are thought to have been granaries. Found at one city is an enormous, well-built bath, which may have been a public bath. Although the "Citadels" are walled, it is far from clear that these structures were defensive. They may have been built to divert flood waters.

Most city dwellers appear to have been traders or artisans, who lived with others pursuing the same occupation in well-defined neighborhoods. Materials from distant regions were used in the cities for constructing seals, beads and other objects. Among the artifacts made were beautiful beads made of glazed stone (called faïence). The seals have images of animals, gods etc., and inscriptions. Some of the seals were used to stamp clay on trade goods, but they probably had other uses. Although some houses were larger than others, Indus civilization cities were remarkable for their apparent egalitarianism. For example, all houses had access to water and drainage facilities. One gets the impression of a vast, middle-class society.

Economy

The Indus civilization's economy appears to have depended significantly on trade, which was facilitated by major advances in transport technology. These advances included bullock-driven carts that are identical to those seen throughout South Asia today, as well as boats. Most of these boats were probably small, flat-bottomed craft, perhaps driven by sail, similar to those one can see on the Indus River today; however, there is secondary evidence of sea-going craft. Archaeologists have discovered a massive, dredged canal and docking facility at a coastal city.

Judging from the dispersal of Indus civilization artifacts, the trade networks economically integrated a huge area, including portions of Afghanistan, the coastal regions of Persia, northern and central India, and Mesopotamia. A Sumerian inscription appears to use the name Meluhha to refer to the Indus civilization. If so, it is the only evidence we possess that might suggest what Indus civilization people called themselves.
Agriculture

The nature of the Indus civilization's agricultural system is still largely a matter of conjecture due to the paucity of information surviving through the ages. Some speculation is possible, however.

Indus civilization agriculture must have been highly productive; after all, it was capable of generating surpluses sufficient to support tens of thousands of urban residents who were not primarily engaged in agriculture. It relied on the considerable technological achievements of the pre-Harappan culture, including the plough. Still, very little is known about the farmers who supported the cities or their agricultural methods. Some of them undoubtedly made use of the fertile alluvial soil left by rivers after the flood season, but this simple method of agriculture is not thought to be productive enough to support cities. There is no evidence of irrigation, but such evidence could have been obliterated by repeated, catastrophic floods.

The Indus civilization appears to disconfirm the hydraulic despotism hypothesis, which is concerned with the origin of urban civilization and the state. According to this hypothesis, cities could not have arisen without irrigation systems capable of generating massive agricultural surpluses. To build these systems, a despotic, centralized state emerged that was capable of suppressing the social status of thousands of people and harnessing their labor as slaves. It is very difficult to square this hypothesis with what is known about the Indus civilization. There is no evidence of kings, slaves, or forced mobilization of labor.

It is often assumed that intensive agricultural production requires dams and canals. This assumption is easily refuted. Throughout Asia, rice farmers produce significant agricultural surpluses from terraced, hillside rice paddies, which result not from slavery but rather the accumulated labor of many generations of people. Instead of building canals, Indus civilization people may have built water diversion schemes, which — like terrace agriculture — can be elaborated by generations of small-scale labor investments. In addition, it is known that Indus civilization people practiced rainfall harvesting, a powerful technology that was brought to fruition by classical Indian civilization but nearly forgotten in the 20th century. It should be remembered that Indus civilization people, like all peoples in South Asia, built their lives around the monsoon, a weather pattern in which the bulk of a year's rainfall occurs in a four-month period. At a recently discovered Indus civilization city in western India, archaeologists discovered a series of massive reservoirs, hewn from solid rock and designed to collect rainfall, that would have been capable of meeting the city's needs during the dry season.

Writing

The Indus civilization remains mysterious in another way: Despite numerous attempts, scholars have not been able to definitively decipher the Indus script. One problem is the lack of evidence. Most of the known inscriptions have been found on seals or ceramic pots, and are no more than 4 or 5 characters in length; the longest is 26 characters. There is no evidence of a body of literature.

Because the inscriptions are so short, some scholars wonder whether the Indus script fell short of a true writing system; it has been suggested that the system amounted to little more than a means of recording identity in economic transactions. Still, it is possible that longer texts were written in perishable media. Morever, there is one, small piece of evidence suggesting that the script embodies a well-known, widespread, and complex communication system. At a recently discovered Indus civilization city in Western India, evidence has been found that appears to be the remnants of a large sign that was mounted above the gate to the city. Perhaps it was designed to inform travelers (who would have been numerous) of the city's name, analogous to the welcome signs seen today along highways leading to major cities.

Decline and collapse

For 700 years, the Indus civilization provided its peoples with prosperity and abundance and its artisans produced goods of surpassing beauty and excellence. But nearly as suddenly as the civilization emerged, it declined and disappeared. No one knows why, but it may have coincided with the arrival of nomadic Indo-European speakers in the area.

Around 1900 BC, signs began to emerge of mounting problems. People started to leave the cities. Those who remained were poorly nourished. By around 1800 BC, most of the cities were abandoned. In the centuries to come — and again, in sharp contrast to its contemporaries, Mesopotamia and ancient Egypt — recollection of the Indus civilization and its achievements seemed to disappear from the record of human experience. Unlike the ancient Egyptians and Mesopotamians, Indus civilization people built no huge monuments to attest to their existence. One could argue that they could not do so because stone was hard to come by in the Indus Valley alluvium, although this is also true of Mesopotamia. One could also argue that the concept of an enormous, intimidating monument was foreign to their view of the world.

To be sure, Indus civilization people did not disappear. In the aftermath of the Indus civilization's collapse, regional cultures emerged, all of which show the lingering influence — to varying degrees — of the Indus civilization. In the formerly great city of Harappa, burials have been found that correspond to a regional culture called the Cemetery H culture. Some former Indus civilization people appear to have migrated to the east, toward the Gangetic Plain. What disappeared was not the people, but the civilization: the cities, the writing system, the trade networks, and — ultimately — the ideology that so obviously provided the intellectual foundation for this civilization's integration.

In the early twentieth century, scholars argued that the collapse was so sudden that it must have been caused by foreign conquest, in an "Aryan invasion". This idea was based on the longstanding claim that "superior" Aryan invaders, with their horses and chariots, conquered the "primitive," "dark," and "weak" peoples they encountered in ancient South Asia. Subsequently, these "white" invaders intermingled with the indigenous "dark" population, and grew "weak" — and therefore ripe for repeated conquest. It was part of a larger, mythological narrative that was used to legitimize the English colonization of the "weak" and "dark" peoples of India. These ideas were developed before the discovery of the Indus civilization itself, when it was assumed that the pre-Aryan Indian populations lived primitive lives. When the civilization was discovered in the 1920s, these arguments were adapted to present the Indo-Aryans as energetic barbarian warriors who overthrew a passive or peaceful urban culture. In the words of the archaeologist Mortimer Wheeler, the Indo-Aryan war god Indra 'stands accused' of the destruction.

Current thinking does not give much credence to the view that the Indo-Aryans were responsible for the collapse of the Indus civilization. What caused the collapse? It seems undeniable that a major factor was climatic change. In 2600 BC, the Indus Valley was verdant, forested, and teeming with wildlife. It was wetter, too. Floods were a problem and appear, on more than one occasion, to have overwhelmed certain settlements. As a result, Indus civilization people supplemented their diet with hunting. By 1800 BC, the climate is known to have changed. It became significantly cooler and drier. But this fact alone may not have been sufficient to bring down the Indus civilization.

The crucial factor may have been the disappearance of substantial portions of the Ghaggar-Hakra or Sarasvati river system. A tectonic event may have diverted the system's sources toward the Ganges Plain, though there is some uncertainty about the date of this event. Such a statement may seem dubious if one does not realize that the transition between the Indus and Gangetic plains amounts to a matter of inches, and is all but imperceptible. The region in which the river's waters formerly arose is known to be geologically active, and there is evidence of major tectonic events at the time the Indus civilization collapsed. It is apropos that until 1998 the blind Ganges River Dolphin and Indus River Dolphin have been considered two different species, partly because of their apparently discrete distribution. Now the two populations have been identified as belonging to a single species, Platanista gangetica.

The legendary Sarasvati River's historical existence was unknown until the late 20th century, when geologists used satellite photographs to trace its former course through the Indus Valley. If the Sarasvati river system dried up when the Indus civilization was at its height, the consequences would have been devastating. Refugees would have flooded the other cities. The "critical mass" needed for economic integration would have collapsed.
The most likely explanation is that the causes were multiple — and, in their aggregation, catastrophic. In the declining years, Indus civilization people tried to hang on to their old way of life, but in the end, they gave up. By 1600 BC, the cities were deserted. In the 19th century, British engineers discovered that the abundant bricks found in the ruins — in which they expressed no evident curiosity — provided excellent raw materials for railway construction. They proceeded to destroy much of the available archaeological evidence.

Legacy

The relationship between the Indus civilization and the early Sanskrit language culture that produced the Vedic texts of Hinduism is unclear. Due to language evolution it seems unlikely that the Indus civilisation was Indo-European. It is puzzling that the most ancient Vedic texts speak of a beautiful river, the Sarasvati. They recall a thriving, utopian lifestyle that emerged along its banks. Later texts also describe the sad story of the river's disappearance.

Are the ancient Vedic references to the Sarasvati River purely mythological? We are in the realm of conjecture. According to comparative linguistics the Indo-Europeans who arrived in India were related to other peoples who migrated to the Middle East and Europe during the same period; all these peoples brought with them a patriarchal polytheistic religion related with Norse mythology and Greek mythology. In India, these beliefs evolved into the sophisticated religious tradition, Hinduism, which looks to the most ancient Vedas as a source of legitimacy. It is clear that the Indus civilization's legacy contributed to Hinduism's development. As several archaeologists have noted, there is something ineffably "Indian" about the Indus valley civilization. Judging from the abundant figurines depicting female fertility that they left behind, Indus civilization people — like modern Hindus — may have held a special place in their worship for a mother goddess and the life-affirming principles she represents (see Shakti and Kali). Their seals depict animals in a way that seems to suggest veneration, perhaps presaging Hindu convictions regarding the sacredness of cattle. Like Hindus today, Indus civilization people seemed to have placed a high value on bathing, personal cleanliness, and residing with one's extended family.

Perhaps the most important legacy of the Indus civilization, if such a legacy exists, was its apparent nonviolence (in contrast to the warlike Indo-Europeans). Unlike other ancient civilizations, the archaeological record of the Indus civilization provides little evidence of armies, kings, slaves, social conflict, prisons, and other oft-negative traits that we traditionally associate with early civilization although this could simply be due to the sheer completeness of its collapse and subsequent disappearance.