Decline of Indus Valley Civilization, Causes, Theories

The Indus Valley Civilization (IVC), also known as the Harappan Civilization, was a Bronze Ageurban culture that flourished in the Indus River basin of modern-day Pakistan and northwest India from around 3300 BCE to 1700 BCE. It was one of the earliest and most advanced civilizations, with well-planned cities, a sophisticated drainage system, and a writing system that remains undeciphered.

The IVC began declining around 1900 BCE, the archaeological evidence indicates a gradual, rather than abrupt, collapse; historians present various factors that caused the decline of this civilization.

Theories of Decline

Various theories attempt to explain the sudden decline of the Indus Valley Civilization (IVC) around 1900 BCE, however, scholars debate which factors resulted in the civilization’s demise. Some theories suggest environmental changes, invasions, and the drying up of rivers could have caused the decline. 

Natural Disasters

Some theories suggest that natural disasters like floods and earthquakes could have led to the destruction and disintegration of urban centres. 

• Evidence: 
  • Flood: 
    • Occupation levels divided by silt deposits.
    • Houses and Streets covered by silt deposits up to 30 ft above ground level. 
    • Houses built on silt-covered debris.
  • Earthquake: 
    • Indus area is a disturbed earthquake zone. Earthquakes raised the level of flood plains blocking the passage of river water to the sea, forcing water into cities. 
    • Earthquakes caused shift of land away from sea coast affecting commercial cities.
• Criticism: Decline of settlements outside the Indus Valley will not be explained by this theory. A river cannot be dammed by tectonic effects.

Change in course of the Indus River

The Indus River, a crucial water source for civilization, may have shifted its course away from the major urban centres, leading to water scarcity and the inability to sustain the cities.

• Evidence: Silt is there in Harappa because of wind action which brought sand and silt. Sand silt not due to floods. 
• Criticism: This can explain only the desertion of Mohenjodaro but not its decline.

Climate Change

Environmental changes like increased aridity and the drying up of the Ghaggar-Hakra river system (ancient Saraswati River) could have impacted agriculture and water availability, leading to the decline of civilization. 

• Evidence: Middle of 2nd Millennium B.C. a period of increased arid conditions. In such a situation a semi-arid region (like Harappa) would be affected most. the decline of agriculture would result. Tectonic movement would affect river systems which would dry up. 
• Criticism: Not fully worked out, drying up of river Ghaggar not dated yet. 

Aryan Invasion Theory:

Some scholars suggest that the civilization was invaded and conquered by a nomadic Indo-European group known as the Aryans, leading to its downfall. Archaeological evidence of destruction layers at sites like Mohenjo-Daro and Harappais cited to support this theory.

• Evidence: - Human skeletons have been found lying on the streets. Rig Veda refers to fortresses of 'Dasas' which the god Purandra destroys. The geographical area of Rig Veda Aryans includes the Punjab-Ghaggar region. Vedas mention a place called Hariyapiya on Ravi River where Aryans fought a battle. Name similar to Harappa. 
• Criticism: Decline of Harappa around 1800 B.C. whereas Aryans not earlier than 1500 B.C. So Harappans and Aryan's clash seems difficult to accept.

Theory of Gradual Decline

The theory of Ecological Imbalance suggests the gradual decline of the Indus Valley Civilization was caused by deforestation, overexploitation of resources, climate change leading to aridity, drying up of the Saraswati River, and unsustainable practices that degraded the environment and disrupted the agricultural base over time.

• The Harappans may have migrated toward the Ganges basin in the east, where they could have established villages and isolated farms. 

 The Tradition survives 

Scholars now focus on continuity rather than decline causes, realizing Indus traditions persisted after cities declined. The traditions of the IVC survived and influenced the cultural developments that followed in South Asia.

• Continuity can be seen in settlement patterns, with some IVC sites remaining inhabited. 
• Religious iconography, like female figurines and yogic postures, may have influenced later Hindu practices. 
• Crafts such as bead-making, pottery, and metallurgy continued, indicating knowledge transfer. 
• Artistic styles and motifs from IVC seals and artefacts are traceable in later Indian art and architecture. 
• Advanced urban planning principles and architectural styles of IVC cities inspired city planning in subsequent civilizations. 
• Agricultural practices like wheat, barley, and cotton cultivation persisted. 

While the cities declined, the IVC's cultural legacy was absorbed and carried forward by successive civilizations in the Indian subcontinent.

Decline of Indus Valley Civilization UPSC PYQs

Question 1: To what extent has the urban planning and culture of the Indus Valley Civilization provided inputs to present-day urbanization? Discuss. (UPSC Mains 2014)

Question 2: Which one of the following ancient towns is well-known for its elaborate system of water harvesting and management by building a series of dams and channelling water into connected reservoirs? (UPSC Prelims 2021)

1. Dholavira
2. Kalibangan
3. Rakhigarhi
4. Ropar

Answer (a)

Decline of Indus Valley Civilization

Q1. What are the reasons for the decline of the Harappan civilization?

Ans. The decline of the Harappan civilization was influenced by factors such as floods, droughts, deforestation, Aryan migration, and climate change, leading to societal shifts and the eventual abandonment of cities.

Q2. What is the theory of the gradual decline of Harappan civilization?

Ans. The theory of gradual decline suggests the Harappan civilization declined over time due to factors like environmental degradation, climate change, resource depletion, and unsustainable practices.

Q3. What was the role of climate in the decline of the Indus Valley Civilization?

Ans. Climate change leading to increased aridity, droughts, and drying up of rivers like the Saraswati played a significant role in the decline of the Indus Valley Civilization.