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200-Year Drought Doomed Indus Valley Civilization - Scientific American
This source says that a drought caused the Indus valley civilization to crumble.

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The decline of Bronze-Age civilizations in Egypt, Greece and Mesopotamia has been attributed to a long-term drought that began around 2000 BC. Now paleoclimatologists propose that a similar fate was followed by the enigmatic Indus Valley Civilization, at about the same time. Based on isotope data from the sediment of an ancient lake, the researchers suggest that the monsoon cycle, which is vital to the livelihood of all of South Asia, essentially stopped there for as long as two centuries.

The Indus Valley, in present Pakistan and northwest India, was home to a civilization also known as the Harappan Civilization. It was characterized by large, well-planned cities with advanced municipal sanitation systems and a script that has never been deciphered. But the Harappans seemed to slowly lose their urban cohesion, and their cities were gradually abandoned.

The link between this gradual decline and climate has been tenuous because of a dearth of climate records from the region. So Yama Dixit, a paleoclimatologist at the University of Cambridge, UK, and her colleagues examined sediments from Kotla Dahar, an ancient lake near the northeastern edge of the Indus Valley area in Haryana, India, that still seasonally floods.

The team assigned ages to sediment layers using radiocarbon dating of organic matter. In various layers, they collected the preserved shells of tiny lake snails ( Melanoides tuberculata), which are made of a form of calcium carbonate (CaCO3) called aragonite. The team also looked at the oxygen in the argonite molecules, counting the ratio of the rare oxygen-18 isotope to the more prevalent oxygen-16.

Two-hundred-year hiatus
Kotla Dahar is a closed basin, filled only by rain and runoff and without outlets. Thus precipitation and evaporation alone determine its water volume. During drought, oxygen-16, which is lighter than oxygen-18, evaporates faster, so that the remaining water in the lake and, consequently, the snails' shells, become enriched with oxygen-18. The team's reconstruction showed a spike in the relative amount of oxygen-18 between 4,200 and 4,000 years ago. This suggests that precipitation dramatically decreased during that time. Moreover, their data suggests that the regular summer monsoons stopped for some 200 years.

The result, reported last week in Geology, supports the idea that monsoon failure led to the civilization's decline, although David Hodell, a co-author of the study and a paleoclimatologist also at the University of Cambridge, hastens to add that uncertainties in the shell and archaeological records mean that the dates could be off by some 100 years in either direction.

Anil Gupta, the director of the Wadia Institute of Himalayan Geology in Dehradun, India, says that the work fills a gap in the geographic record of ancient droughts. But large questions remain. "What drove this climate change 4,100 years ago? We don't see major changes in the North Atlantic or in the solar activity at that time."

Recently, another team, led by paleoclimatologist Sushma Prasad of the German Research Center for Geoscience in Potsdam, Germany, did a similar analysis on a sediment core from Lonar Lake in central India. They found that in that area, drought began as many as 4,600 years ago. But the results are consistent with those of Dixit's group, Prasad says. "We see a drying event starting earlier, but at about 4,200 years ago it became very intense."

If a lack of monsoons did spell the end of the Indus Valley civilization, says Hodell, "it is an example - and there are other examples of this - of how ancient societies have had to contend with climate. There are some lessons for us and our future, in which we will have to deal with anthropogenic climate change".

This article is reproduced with permission from the magazine . The article was first published on March 3, 2014.

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200-Year Drought Doomed Indus Valley Civilization

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The decline of Bronze-Age civilizations in Egypt, Greece and Mesopotamia has been attributed to a long-term drought that began around 2000 BC. Now paleoclimatologists propose that a similar fate was followed by the enigmatic Indus Valley Civilization, at about the same time.

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https://www.livescience.com/what-was-the-indus-valley-civilization

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The Indus Valley Civilization - famous for its large, well-planned cities - is considered one of the six early pristine state-level civilizations.

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May 28, 2012

A new study combining the latest archaeological evidence with state-of-the-art geoscience technologies provides evidence that climate change was a key ingredient in the collapse of the great Indus or Harappan Civilization almost 4000 years ago. The study also resolves a long-standing debate over the source and fate of the Sarasvati, the sacred river of Hindu mythology.

Once extending more than 1 million square kilometers across the plains of the Indus River from the Arabian Sea to the Ganges, over what is now Pakistan, northwest India and eastern Afghanistan, the Indus civilization was the largest-but least known-of the first great urban cultures that also included Egypt and Mesopotamia. Like their contemporaries, the Harappans, named for one of their largest cities, lived next to rivers owing their livelihoods to the fertility of annually watered lands.

"We reconstructed the dynamic landscape of the plain where the Indus civilization developed 5200 years ago, built its cities, and slowly disintegrated between 3900 and 3000 years ago," said Liviu Giosan, a geologist with Woods Hole Oceanographic Institution (WHOI) and lead author of the study published the week of May 28 in the Proceedings of the National Academy of Science. "Until now, speculations abounded about the links between this mysterious ancient culture and its life-giving mighty rivers."

Today, numerous remains of the Harappan settlements are located in a vast desert region far from any flowing river. In contrast to Egypt and Mesopotamia, which have long been part of the Western classical canon, this amazingly complex culture in South Asia with a population that at its peak may have reached 10 percent of the world's inhabitants, was completely forgotten until 1920's. Since then, a flurry of archaeological research in Pakistan and India has uncovered a sophisticated urban culture with myriad internal trade routes and well-established sea links with Mesopotamia, standards for building construction, sanitation systems, arts and crafts, and a yet-to-be deciphered writing system.

"We considered that it is high time for a team of interdisciplinary scientists to contribute to the debate about the enigmatic fate of these people," added Giosan.

The research was conducted between 2003 and 2008 in Pakistan, from the coast of the Arabian Sea into the fertile irrigated valleys of Punjab and the northern Thar Desert. The international team included scientists from the U.S., U.K., Pakistan, India, and Romania with specialties in geology, geomorphology, archaeology, and mathematics. By combining satellite photos and topographic data collected by the Shuttle Radar Topography Mission (SRTM), the researchers prepared and analyzed digital maps of landforms constructed by the Indus and neighboring rivers, which were then probed in the field by drilling, coring, and even manually-dug trenches. Collected samples were used to determine the sediments' origins, whether brought in and shaped by rivers or wind, and their age, in order to develop a chronology of landscape changes.

"Once we had this new information on the geological history, we could re-examine what we know about settlements, what crops people were planting and when, and how both agriculture and settlement patterns changed," said co-author Dorian Fuller, an archaeologist with University College London. "This brought new insights into the process of eastward population shift, the change towards many more small farming communities, and the decline of cities during late Harappan times."

The new study suggests that the decline in monsoon rains led to weakened river dynamics, and played a critical role both in the development and the collapse of the Harappan culture, which relied on river floods to fuel their agricultural surpluses.

From the new research, a compelling picture of 10,000 years of changing landscapes emerges. Before the plain was massively settled, the wild and forceful Indus and its tributaries flowing from the Himalaya cut valleys into their own deposits and left high "interfluvial" stretches of land between them. In the east, reliable monsoon rains sustained perennial rivers that crisscrossed the desert leaving behind their sedimentary deposits across a broad region.

Among the most striking features the researchers identified is a mounded plain, 10 to 20 meters high, over 100 kilometers wide, and running almost 1000 kilometers along the Indus, they call the "Indus mega-ridge," built by the river as it purged itself of sediment along its lower course.

"At this scale, nothing similar has ever been described in the geomorphological literature," said Giosan. "The mega-ridge is a surprising indicator of the stability of Indus plain landscape over the last four millennia. Remains of Harappan settlements still lie at the surface of the ridge, rather than being buried underground."

Mapped on top of the vast Indo-Gangetic Plain, the archaeological and geological data shows instead that settlements bloomed along the Indus from the coast to the hills fronting the Himalayas, as weakened monsoons and reduced run-off from the mountains tamed the wild Indus and its Himalayan tributaries enough to enable agriculture along their banks.

"The Harappans were an enterprising people taking advantage of a window of opportunity - a kind of "Goldilocks civilization," said Giosan. "As monsoon drying subdued devastating floods, the land nearby the rivers - still fed with water and rich silt - was just right for agriculture. This lasted for almost 2,000 years, but continued aridification closed this favorable window in the end."

In another major finding, the researchers believe they have settled a long controversy about the fate of a mythical river, the Sarasvati. The Vedas, ancient Indian scriptures composed in Sanskrit over 3000 years ago, describe the region west of the Ganges as " the land of seven rivers." Easily recognizable are the Indus and its current tributaries, but the Sarasvati, portrayed as " surpassing in majesty and might all other waters" and " pure in her course from mountains to the ocean, " was lost. Based on scriptural descriptions, it was believed that the Sarasvati was fed by perennial glaciers in the Himalayas. Today, the Ghaggar, an intermittent river that flows only during strong monsoons and dissipates into the desert along the dried course of Hakra valley, is thought to best approximate the location of the mythic Sarasvati, but its Himalayan origin and whether it was active during Vedic times remain controversial.

Archaeological evidence supports the Ghaggar-Hakra as the location of intensive settlement during Harappan times. The new geological evidence-sediments, topography- shows that rivers were indeed sizable and highly active in this region, but most likely due to strong monsoons. However, there is no evidence of wide incised valleys like along the Indus and its tributaries and researchers did not find any cut-through, incised connections to either of the two nearby Himalayan-fed rivers of Sutlej and Yamuna. The new study argues that these crucial differences prove that the Sarasvati (Ghaggar-Hakra) was not Himalayan-fed, but a perennial monsoon-supported watercourse, and that aridification reduced it to short seasonal flows.

By 3900 years ago, their rivers drying, the Harappans had an escape route to the east toward the Ganges basin, where monsoon rains remained reliable.

"We can envision that this eastern shift involved a change to more localized forms of economy: smaller communities supported by local rain-fed farming and dwindling streams," said Fuller. "This may have produced smaller surpluses, and would not have supported large cities, but would have been reliable."

Such a system was not favorable for the Indus civilization, which had been built on bumper crop surpluses along the Indus and the Ghaggar-Hakra rivers in the earlier wetter era. This dispersal of population meant that there was no longer a concentration of workforce to support urbanism. "Thus cities collapsed, but smaller agricultural communities were sustainable and flourished. Many of the urban arts, such as writing, faded away, but agriculture continued and actually diversified," said Fuller.

"An amazing amount of archaeological work has been accumulating over the last decades, but it's never been linked properly to the evolution of the fluvial landscape. We now see landscape dynamics as the crucial link between climate change and people," said Giosan. "Today the Indus system feeds the largest irrigation scheme in the world, immobilizing the river in channels and behind dams. If the monsoon were to increase in a warming world, as some predict, catastrophic floods such as the humanitarian disaster of 2010, would turn the current irrigation system, designed for a tamer river, obsolete."

This work was funded by the National Science Foundation, the Leverhulme Trust, Woods Hole Oceanographic Institution, the University of Aberdeen, and Louisiana State University.
The Woods Hole Oceanographic Institution is a private, non-profit organization on Cape Cod, Mass., dedicated to marine research, engineering, and higher education. Established in 1930 on a recommendation from the National Academy of Sciences, its primary mission is to understand the oceans and their interaction with the Earth as a whole, and to communicate a basic understanding of the oceans' role in the changing global environment. For more information, please visit www.whoi.edu.

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Climate Change Led to Collapse of Ancient Indus Civilization, Study Finds

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May 28, 2012 A new study combining the latest archaeological evidence with state-of-the-art geoscience technologies provides evidence that climate change was a key ingredient in the collapse of the great Indus or Harappan Civilization almost 4000 years ago. The study also resolves a long-standing debate over the source and fate of the Sarasvati, the sacred river of Hindu mythology.

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This theory suggests that there was an attack on the Indus civilisation from a nomadic tribe called the Aryans. They invaded and conquered the Indus Valley

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwj0vp2E_NL-AhV_S2wGHYErDugQFnoECCQQAQ&url=https%3A%2F%2Fwww.khanacademy.org%2Fhumanities%2Fworld-history%2Fworld-history-beginnings%2Fancient-india%2Fa%2Fthe-indus-river-valley-civilizations&usg=AOvVaw35Wpfd7WkPdXThW_pyjZ-a

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There was a recorded shift in temperature at around 2500 BC. This caused the weather patterns to change and dry up the monsoons, disrupting the agricutlutre.
Ancient Indus Valley Civilization & Climate Change's Impact (whoi.edu)

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November 13, 2018

More than 4,000 years ago, the Harappa culture thrived in the Indus River Valley of what is now modern Pakistan and northwestern India, where they built sophisticated cities, invented sewage systems that predated ancient Rome's, and engaged in long-distance trade with settlements in Mesopotamia. Yet by 1800 BCE, this advanced culture had abandoned their cities, moving instead to smaller villages in the Himalayan foothills. A new study from the Woods Hole Oceanographic Institution (WHOI) found evidence that climate change likely drove the Harappans to resettle far away from the floodplains of the Indus.

"There's a powerful lesson for today. If you look at Syria and Africa, the migration out of those areas has some roots in climate change."

- Liviu Giosan

Beginning in roughly 2500 BCE, a shift in temperatures and weather patterns over the Indus valley caused summer monsoon rains to gradually dry up, making agriculture difficult or impossible near Harappan cities, says Liviu Giosan, a geologist at WHOI and lead author on the paper that published Nov. 13, 2018, in the journal Climate of the Past.

"Although fickle summer monsoons made agriculture difficult along the Indus, up in the foothills, moisture and rain would come more regularly," Giosan says. "As winter storms from the Mediterranean hit the Himalayas, they created rain on the Pakistan side, and fed little streams there. Compared to the floods from monsoons that the Harappans were used to seeing in the Indus, it would have been relatively little water, but at least it would have been reliable. "

Evidence for this shift in seasonal rainfall-and the Harapans' switch from relying on Indus floods to rains near the Himalaya in order to water crops-is difficult to find in soil samples. That's why Giosan and his team focused on sediments from the ocean floor off Pakistan's coast. After taking core samples at several sites in the Arabian Sea, he and his group examined the shells of single-celled plankton called foraminifera (or "forams") that they found in the sediments, helping them understand which ones thrived in the summer, and which in winter.

Once he and the team identified the season based on the forams' fossil remains, they were able to then focus on deeper clues to the region's climate: paleo-DNA, fragments of ancient genetic material preserved in the sediments.

"The seafloor near the mouth of the Indus is a very low-oxygen environment, so whatever grows and dies in the water is very well preserved in the sediment," says Giosan. "You can basically get fragments of DNA of nearly anything that's lived there."

During winter monsoons, he notes, strong winds bring nutrients from the deeper ocean to the surface, feeding a surge in plant and animal life. Likewise, weaker winds other times of year provide fewer nutrients, causing slightly less productivity in the waters offshore.

"The value of this approach is that it gives you a picture of the past biodiversity that you'd miss by relying on skeletal remains or a fossil record. And because we can sequence billions of DNA molecules in parallel, it gives a very high-resolution picture of how the ecosystem changed over time," adds William Orsi, paleontologist and geobiologist at Ludwig Maximilian University of Munich, who collaborated with Giosan on the work.

Sure enough, based on evidence from the DNA, the team found that winter monsoons seemed to become stronger-and summer monsoons weaker-towards the later years of the Harappan civilization, corresponding with the move from cities to villages.

"We don't know whether Harappan caravans moved toward the foothills in a matter of months or this massive migration took place over centuries. What we do know is that when it concluded, their urban way of life ended," Giosan says.

The rains in the foothills seem to have been enough to hold the rural Harapans over for the next millennium, but even those would eventually dry up, likely contributing to their ultimate demise.

"We can't say that they disappeared entirely due to climate-at the same time, the Indo-Aryan culture was arriving in the region with Iron Age tools and horses and carts. But it's very likely that the winter monsoon played a role," Giosan says.

The big surprise of the research, Giosan notes, is how far-flung the roots of that climate change may have been. At the time, a "new ice age" was settling in, forcing colder air down from the Arctic into the Atlantic and northern Europe. That in turn pushed storms down into the Mediterranean, leading to an upswing in winter monsoons over the Indus valley.

"It's remarkable, and there's a powerful lesson for today," he notes. "If you look at Syria and Africa, the migration out of those areas has some roots in climate change. This is just the beginning-sea level rise due to climate change can lead to huge migrations from low lying regions like Bangladesh, or from hurricane-prone regions in the southern U.S. Back then, the Harappans could cope with change by moving, but today, you'll run into all sorts of borders. Political and social convulsions can then follow."

Also collaborating on the study was Ann G. Dunlea, Samuel E. Munoz, Jeffrey. P. Donnelly, and Valier Galy of WHOI; William D. Orsi of Ludwig-Maximilians-Universität MuÌˆnchen; Marco Coolen and Cornelia Wuchter of Curtin University in Australia; Kaustubh Thirumalai of Brown University; Peter D. Clift of Louisiana State University; and Dorian Q. Fuller of University College, London.

The work was supported by the National Science Foundation's Division of Ocean Sciences and internal WHOI funds.
The Woods Hole Oceanographic Institution is a private, non-profit organization on Cape Cod, Mass., dedicated to marine research, engineering, and higher education. Established in 1930 on a recommendation from the National Academy of Sciences, its primary mission is to understand the oceans and their interaction with the Earth as a whole, and to communicate a basic understanding of the oceans' role in the changing global environment. For more information, please visit www.whoi.edu.

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Ancient Indus Valley Civilization & Climate Change's Impact

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The Ancient Indus Valley Civilization was thriving 4,000 years ago until a sudden migration led to its demise. A new study from the WHOI found evidence that climate change likely drove the Harappans to resettle far away from the floodplains of the Indus.

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The first is gradual environmental change, such as a shift in climatic patterns and consequent agricultural disaster, perhaps resulting from excessive environmental stress caused by population growth and overexploitation of resources. Second, some scholars have postulated more-precipitous environmental changes, such as tectonic events leading to the flooding of Mohenjo-daro, the drying up of the Sarawati River, or other such calamities. Third, it is conceivable that human activities, such as invasions of tribespeople from the hills to the west of the Indus valley, perhaps even Indo-Aryans, contributed to the breakdown of Indus external trade links or more directly disrupted the cities. The fourth theory posits the occurrence of an epidemic or a similar agent of devastation. It appears likely that some complex of natural forces compromised the fabric of society and that subsequent human intervention hastened its complete breakdown.

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There is no general agreement regarding the causes of the breakdown of Harappan urban society. Broadly speaking, the principal theories thus far proposed fall under four headings. The first is gradual environmental change, such as a shift in climatic patterns and consequent agricultural disaster, perhaps resulting from excessive environmental stress caused by population growth and overexploitation of resources. Second, some scholars have postulated more-precipitous environmental changes, such as tectonic events leading to the flooding of Mohenjo-daro, the drying up of the Sarawati River, or other such calamities. Third, it is conceivable that human activities, such as invasions of tribespeople from the hills to the west of the Indus valley, perhaps even Indo-Aryans, contributed to the breakdown of Indus external trade links or more directly disrupted the cities. The fourth theory posits the occurrence of an epidemic or a similar agent of devastation. It appears likely that some complex of natural forces compromised the fabric of society and that subsequent human intervention hastened its complete breakdown.

Post-Harappan developments

The Post-Urban Period in northwestern India

It is still far from certain at what date the urban society broke down. The decline probably occurred in several stages, perhaps over a century or more; the period between about 2000 and 1750 bce is a reasonable estimation. The collapse of the urban system does not necessarily imply a complete breakdown in the lifestyle of the population in all parts of the Indus region, but it seems to have involved the end of whatever system of social and political control had preceded it. After that date the cities, as such, and many of their distinctively urban traits-the use of writing and of seals and a number of the specialized urban crafts-disappear. The succeeding era, which lasted until about 750 bce, may be considered as Post-Harappan or, perhaps better, as "Post-Urban."

In Pakistan's Sind province the Post-Urban phase is recognizable in the Jhukar culture at Chanhu-daro and other sites. There certain copper or bronze weapons and tools appear to be of "foreign" type and may be compared to examples from farther west (Iran and Central Asia); a different but parallel change is seen at Pirak, not far from Mehrgarh. In the Kachchh and Saurashtra regions there appears to have been a steady increase in the number of settlements, but all are small and none can compare with such undoubtedly Harappan cities as Dholavira. In this region, however, the distinctive foreign metal elements are less prominent.

An intriguing development occurs along the Saraswati valley: there the early Post-Urban stage is associated with the pottery known from the Cemetery H at Harappa. This coincides with a major reduction in both the number and size of settlements, suggesting a deterioration in the environment. In the eastern Punjab too there is a disappearance of the larger, urban sites but no comparable reduction in the number of smaller settlements. This is also true of the settlements farther east in the Ganges-Yamuna valleys. It is probably correct to conclude that, in each of these areas during the Post-Urban Period, material culture exhibited some tendency to develop regional variations, sometimes showing continuations of features already present during the Pre-Urban and Urban phases.

The appearance of Indo-Aryan speakers

Scholars have traditionally agreed that a people speaking Old Indo-Aryan dialects of the Indo-Iranian branch of the Indo-European language family arrived in the Indian subcontinent during the late 3rd and 2nd millennia bce. These newcomers purportedly came from the steppes to the north and east of the Caspian Sea, moving first southward into the southern parts of Central Asia and from there fanning out across the Iranian plateau and spreading throughout northern India, disrupting the established sedentary culture and driving its Dravidian-speaking inhabitants of the Indus civilization southward. The movement itself remains hypothetical, but evidence from cemeteries at Sibri and south of Mehrgarh, near the mouth of the Bolan Pass, shows striking parallels-including foreign copper and bronze tools and weapons and typical pottery forms-with that from cemeteries of the Sapalli-Tepe group in Tajikistan and Uzbekistan. This correspondence suggests a date of about 2000 bce for the presence of these people on the borders of the Indus system.

However, it is even more difficult to identify traces that may be associated with the movement of Indo-Aryan speakers into the central Indus plains or to determine whether the occasional copper or bronze weapons of foreign type found in late contexts at Mohenjo-daro or Chanhu-daro are evidence of their presence there. Moreover, even if Indo-Aryans actually conquered some of the Indus cities and established hegemony over the local population, it has to be explained why they appear to have given up many of their distinctive material products while presumably retaining their distinctive speech.

One hypothesis is that between about 2000 and 1500 bce not an invasion but a continuing spread of Indo-Aryan speakers occurred, carrying them much farther into India, to the east and south, and coinciding with a growing cultural interaction between the native population and the new arrivals. From these processes a new cultural synthesis emerged, giving rise by the end of the 2nd millennium to the conscious expressions of Aryan ethnicity found in the Rigveda, particularly in the later hymns ( see Early Vedic Period).

A more recent and controversial theory put forward by such scholars as American Jim G. Shaffer and Indian B.B. Lal suggests that Aryan civilization did not migrate to the subcontinent but was an original ethnic and linguistic element of pre-Vedic India. This theory would explain the dearth of physical signs of any putative Aryan conquest and is supported by the high degree of physical continuity between Harappan and Post-Harappan society.

The late 2nd millennium and the reemergence of urbanism

Toward the end of the 2nd millennium there appears to have been a further deterioration in the environment throughout the Indus system. Many of the Post-Urban settlements seem to have been abandoned, and traces are found of temporary settlements that were probably associated with nomadic pastoral groups and distinguished by the poverty of their material culture. Along the Saraswati there is further evidence of the drying up of the Derawar oasis, with a further decline in the number and size of settlements. As yet, these events are not properly dated, but they may tentatively be assigned to a period from about 1200-800 bce. In Saurashtra a similar if less extreme decline in the number of settlements is also evident. Even much farther south, in Maharashtra, the opening of the 1st millennium seems to have coincided with a period of desiccation, in which the flourishing agricultural settlements at sites such as Inamgaon declined; temporary encampments of pastoral nomads indicate a general deterioration in the standard of living.

To the north, in Punjab, Haryana, and the upper Gangetic plain, such deterioration is less apparent, perhaps because the proximity of the Himalayas produced a higher level of rainfall. It is in this area that a new tendency emerges-the expansion of settlements associated with the pottery known as Painted Gray Ware. This characteristic ceramic accompanied a spread of settlements toward the east into the upper Ganges-Yamuna valleys and constitutes a distinguishing feature of the process of development that, by the second quarter of the 1st millennium bce, gave rise to the first cities of the Ganges system. (The previous wave of urbanization appears not to have penetrated below the upper Gangetic plain.)

Another factor that coincided with, if not actually contributed to, the new process of change is the beginning and spread of iron working. The earliest dated occurrence of iron is probably that from about 1200 to 1100 bce at Pirak in the Kachchhi region. Comparably early dates are suggested at other widely scattered sites, but it probably took many years for the use of iron in almost all types of toolmaking to become common in all regions. During this period an increasingly marked contrast may be observed between the growing number of cities across the north and the relatively less-developed settlement pattern of peninsular India, where a mixture of small-scale agriculture and pastoralism coincided with the appearance of the various types of "Megalithic" graves and monuments.

Peninsular India in the aftermath of the Indus civilization (c. 2000-1000 bce)

It was stated above that the earliest known settlements in peninsular India appeared early in the 3rd millennium and showed either a mixed agricultural or strongly pastoral character. From about 2000 bce there appears to have been a general expansion of these settlements. It is sometimes suggested that this expansion may have been in some way a result of the end of the Indus civilization and that large numbers of "Harappans" migrated to the south. There is little solid evidence to support this view, and it appears rather that the development was primarily indigenous.What is particularly noteworthy is the way in which regional cultural variants occurred throughout peninsular India and often seem to be ancestral to the major cultural regions known from later historical times. In Maharashtra the excavations at Inamgaon have provided the clearest picture so far of the developments and changes that took place in one of these regions. There can be seen the variety of crops and domestic animals, the changing house types, suggestions of tribal chiefdoms, limited craft specialization, and trade. Copper and bronze artifacts, though still relatively scarce, appear alongside stone blades and axes. This mixed technology continued until the time when iron became common. Farther south, in Karnataka and Tamil Nadu, there is similar evidence, although the staple crop appears to have been millet, and wheat and barley are absent.
Frank Raymond Allchin

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India - The end of the Indus civilization

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There is no general agreement regarding the causes of the breakdown of Harappan urban society. Broadly speaking, the principal theories thus far proposed fall under four headings. The first is gradual environmental change, such as a shift in climatic patterns and consequent agricultural disaster, perhaps resulting from excessive environmental stress caused by population growth and overexploitation of resources.

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Historians believe the Indus Civilisation began to end around 1900BC and by 1700BC  many Indus cities had been abandoned. The question is, did the trade stop?
The Indus Civilisation found trade very important, and their main trade source was Mesopotamia. Around the time the Indus Civilisation began to fall, Mesopotamia was going through political problems. This is why people believe trade between the two were declining or ending.

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What happened to the Indus civilisation?

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What happened to the Indus people? Learn how the Indus civilisation ended and the legacy of its people in this BBC Bitesize KS2 History guide.

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DK Find Out! | Fun Facts for Kids on Animals, Earth, History and more!

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Visit DK Find Out! to learn about dinosaurs, space, animals, nature & more. Fun learning activities for kids with videos, quizzes & galleries at DKFindOut.com