Causes of Decline of the Harappan Civilization

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Uncover the fascinating facts about the Causes of the Decline of the Harappan Civilization. The Harappan Civilization, flourishing in the Indus Valley from 3300 BCE to 1300 BCE, remains a captivating enigma.


Harappan Civilization was one of the world’s earliest urban societies, it surprises us with its well-planned cities, advanced craftwork, and complex social structures. Yet, around 1900 BCE, this vibrant civilization began to fade, leaving behind a trail of unanswered questions. What caused this decline? Was it a single catastrophic event, or a confluence of gradual factors?

Points to Cover

Let’s explore the potential causes of the Harappan civilization’s decline. We will explore various theories, ranging from environmental changes like climate shifts and flooding to social and economic factors like internal conflicts and resource depletion.

By examining archaeological evidence, scientific studies, and historical context, we will attempt to shed light on the mysteries surrounding this fascinating chapter in human history.

✅ Related Post: Salient Features of the Harappan Civilization Notes

Decline of the Harappan Civilization

Timeline of Harappan Civilization

  • Duration: 3300 to 1300 BCE.
  • Geographic Extent: Northeast Afghanistan, Pakistan, and northwest India.

Alternate Name

  • Also known as the Indus River Valley Civilization

Debate on Decline

  • Scholars debate factors leading to the collapse around 1800 BCE

Aryan Invasion Theory

  • One theory suggests an invasion by a nomadic Indo-European group (Aryans).
  • Aryans are proposed to have invaded and subjugated the Harappan Civilization.

Decline of Indus Valley Civilisation History

Abandonment of Mature Harappan Sites

  • Proof indicates that many Mature Harappan sites, especially in regions like Cholistan, were abandoned by 1800 BCE.

Population Rise in Certain Regions

  • Conversely, regions like Gujarat, Haryana, and western Uttar Pradesh experienced a population increase during the same period.

Environmental Change Hypothesis

  • Many academics propose that environmental changes caused the decline of the Harappan Civilization.

Climate Change Theories

  • Some scholars argue that the region’s climate changed due to the drying out of the Saraswati River around 1900 BCE.
  • Others contend that a significant inundation occurred during the same period.

Invasion vs. Dissolution

  • Evidence suggests that an invasion did not cause the decline, as components of the Indus Civilization are found in later societies.
  • Many researchers argue the abrupt dissolution of the large civilization to be the result of changes in river patterns.

Transition to Late Harappan Civilizations

  • The large civilization appears to have transitioned into smaller communities known as the late Harappan civilizations.

✅ Related Post: Introduction of The Harappan Civilization: 3 Phases with Key Details

Causes of Decline of Harappan Civilisation Overview

Monsoons’ Impact on Climate

  • Depending on their impact on flora and crops, monsoons can either be beneficial or harmful to a climate.

Indus Valley Climate Change

  • By 1800 BCE, the Indus Valley experienced a shift to colder and drier conditions.

Disruption of River Networks

  • Seismic events may have disrupted or rerouted the river networks crucial for supporting the Indus Valley Civilization.

Migration to Ganges Basin

  • The Harappans might have migrated to the Ganges basin, establishing villages and solitary farms.

Challenges in Agricultural Surpluses

  • Small towns in the Ganges basin faced challenges in producing the agricultural surpluses required by large communities.

Trade Impact

  • Lower agricultural productivity could have led to a decline in trade with Egypt and Mesopotamia.

Abandonment of Cities

  • Around 1700 BCE, many cities in the Indus Valley Civilization were abandoned.

Aryan Invasion Theory

Origin of Aryan Invasion Theory

  • Ramaprasad Chanda initially proposed the idea that Aryan invaders extinguished the Harappan civilization.

Shift in Attribution

  • Chanda changed his perspective later, and Mortimer Wheeler further developed the Aryan invasion theory.

Wheeler’s Belief

  • Wheeler believed that the Aryan incursion entirely destroyed the Harappan civilization.

Evidence from Mohenjodaro

  • As proof of the Aryan massacre, Wheeler referred to human skeletons found at Mohenjodaro during the final phases of occupancy.

References in Rig Veda

  • Wheeler argued that mentions of different forts, assaults on fortified towns, and the epithet “purandara” (fort destroyer) of the god Indra indicated an Aryan invasion of Harappan cities.

Geographical Connection

  • Punjab and the Ghaggar-Hakra territory were identified as the home of the Rig Vedic Aryans.

Unique Forts in the Region

  • Wheeler noted that no other cultural groups had forts in this region during the relevant historical period.

Rig Vedic References to Harappan Towns

  • Given the absence of other cultural groups with forts, Wheeler believed that the Harappan towns were mentioned in the Rig Veda.

Natural Disasters

Role of Natural Disasters

  • Natural disasters, although not always immediate or singular, can influence the fate of civilizations.

Indus Towns and Silt Debris

  • Towns like Mohenjodaro, Chanhudaro, and Lothal exhibit silt debris, suggesting the impact of swollen rivers during periods of settlement.

Silt Debris as Evidence

  • The silt debris found in various Indus towns highlights the possibility of destruction caused by repeated swollen river events.

Example of Mohenjodaro

  • At Mohenjodaro, multiple strata of silt demonstrate the city’s susceptibility to Indus floods, contributing to the disintegration of the Harappan civilization.

Periods of Habitation Separated by Flooding

  • Different habitation periods in Mohenjodaro show evidence of major flooding, with crumbled building materials and silty clay accumulating between them.

Cyclic Reconstruction After Floods

  • The repeated accumulation of silty mud indicates that the city experienced catastrophic flooding multiple times.
  • In the aftermath, inhabitants rebuilt homes and streets on top of the remains of the previous structures.

Proposed Causes by Sahni, Dales, and Raikes

  • M. R. Sahni, George F. Dales, and Robert L. Raikes suggested that human mistakes may have contributed to the Mohenjodaro floods.

Tectonic Changes Theory

  • Another theory attributes the cause to tectonic changes in the region, making it seismically active.
  • Tectonic movements created a natural barrier, preventing the Indus from flowing toward the sea and forming a large lagoon around Mohenjodaro.

Ecological Imbalance

Environmental Decline Hypothesis

  • Scholars like Fairservis propose environmental concerns as an explanation for the decline of Harappan society.

Population and Resource Estimate

  • Fairservis utilizes current data to estimate the Harappan cultural zone’s population, land, food, and fodder requirements.

Resource Insufficiency Hypothesis

  • The hypothesis suggests that the resources in the Harappan cultural zone could not support the growing population and cattle.

Ecological Imbalance in Semi-Arid Regions

  • Human and cattle populations in semi-arid regions upset the fragile ecological balance by depleting trees, food, and fuel sources.

Harappan Over-Exploitation of Environment

  • Over-exploitation included excessive tree cutting for farming and fuel, as well as over-cultivation and over-grazing.

Community Needs vs. Production Capability

  • Harappan townspeople, farmers, and pastoralists had needs that exceeded the communities’ meagre production capability.

Impact on Landscape

  • The expanding human and animal population, struggling with scarce resources, wore down the landscape.


  • The gradual disappearance of forests and grasslands.
  • Increase in flooding, droughts, and soil salinity.

Moving away from Indus

River Course Changes as Contributing Factor

  • Lambrick proposes that changes in the course of the Indus River may have played a role in the collapse of the Indus Valley civilization.

Unstable Bed of the Indus River

  • The Indus River is characterized by a network of waterways with an unstable bed.

Shift Away from Mohenjodaro

  • Reportedly, the Indus River shifted approximately thirty kilometres away from Mohenjodaro.

Consequences for Mohenjodaro

  • The shift led to a lack of water in Mohenjodaro, prompting city residents and surrounding agrarian villages to move away.

Repetitive Nature of River Shifts

  • Changes in the river’s course happened multiple times during Mohenjodaro’s existence.

Sand and Silt Accumulation

  • The wind carried significant amounts of sand and silt into the city, contributing to the silt deposits visible in Mohenjodaro.

Misidentification of Silt

  • The combination of this silt with buildings made of crumbling mud, mud brick, and baked brick led to its mistaken identification as river silt.

Climatic Change

Impact of Natural Floods on Mohenjodaro

  • Natural floods may have contributed to the wearing down of Mohenjodaro.

Desiccation in Ghaggar-Hakra Region

  • Harappan sites in the Ghaggar-Hakra region experienced progressive desiccation, according to D.P. Agarwal and Sood.

Destruction of the Harappan Civilization

  • Agarwal and Sood assert that the Harappan civilization ended when the Ghaggar-Hakra waterway dried up, leading to increased aridity in the area.

Expansion of Dry Weather

  • They found that the amount of dry weather had increased by the middle of the second millennium B.C.

Impact of Reduced Moisture in Semi-Arid Regions

  • Even a small moisture and water supply reduction in semi-arid regions like Harappa could have catastrophic effects.

Effects on Agricultural Output

  • Reduced moisture would affect agricultural output, putting strain on the economies of cities.

These points highlight the role of desiccation in the Ghaggar-Hakra region, as proposed by Agarwal and Sood, as a contributing factor to the decline of the Harappan civilization. The drying up of waterways and increased aridity had significant implications for the region’s agricultural sustainability and economic stability.

Causes of Decline of Harappan Civilization Summary

The downfall of the Harappan Civilization, also recognized as the Indus River Valley Civilization, is linked to various factors:

Environmental Shifts

Some experts propose that alterations in the environment, like changes in weather patterns leading to agricultural disasters, may have triggered the decline of the civilization. This could result from heightened environmental stress due to population growth and resource overexploitation.

Natural Disasters

Events like tectonic activities causing the flooding of Mohenjo-Daro, the drying up of the Saraswati River, or other calamities are also considered potential causes.


The incursion of tribes from the western hills of the Indus Valley, potentially Indo-Aryans, might have played a role in the breakdown of Harappan urban society.


An epidemic outbreak or a similar devastating agent is also a suggested factor.

Improper Land Use and Deforestation

The excessive use of wood for brick-making may have led to deforestation, compelling the Harappans to migrate.

Shift in Climate

Another hypothesis for the civilization’s downfall is a significant drought in the northern hemisphere approximately 4200 years ago.

It’s crucial to understand that while these reasons may apply to specific areas, they don’t fully elucidate the collapse of the entire civilization. The decline likely unfolded in multiple stages, spanning perhaps over a century or more.

Source: StudyIQ, Poonam Dalal Dahiya Ancient History

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