A recent study claims that the Indus Valley Civilisation (IVC) declined not due to one catastrophic event, but due to centuries-long, recurring droughts that progressively weakened its cities, rivers, agriculture, and social structures.
Key Findings from the Study
- Central Conclusion:
- The study indicates that the IVC did not collapse suddenly due to one catastrophic event.
- Instead it reveals Harappa and other major IVC settlements were affected by a series of multi-decadal droughts between 3000–1000 BCE.
- Climate Reconstruction: Researchers used paleoclimate records (stalactites, stalagmites, lake levels) and climate model simulations to reconstruct rainfall and temperature patterns of the period.
Reasons for Decline of Civilisation
- Recurring Drought Cycles: Four major drought events, each lasting over 85 years, occurred between 2425–1400 BCE.
- The most severe drought peaked around 1733 BCE, lasted ~164 years, and impacted the entire region.
- Hydrological Collapse: Prolonged drought led to Shrinking lakes and playas, Declining river flows, Soil desiccation, Reduced navigability, hurting trade.
- Climate Shift in the Pacific:
- Early IVC prosperity coincided with La Niña-like conditions (3000–2475 BCE), causing wetter-than-modern monsoon seasons.
- As the tropical Pacific warmed, annual rainfall dropped by 10–20%, and temperatures rose by 0.5°C, amplifying arid conditions.
Social and Economic Consequences
- Agricultural Stress: Drought made farming difficult, especially for settlements far from perennial rivers.
- Adaptive Agricultural Practices: Harappans responded by switching crops, diversifying production, and shifting to drought-resilient farming.
- Archaeo-botanical evidence shows a shift from wheat and barley to drought-resistant millets, indicating attempts to cope with aridity.
- Migration and Dispersal: Communities were forced to relocate repeatedly, reshaping the distribution of settlements along the Indus and its tributaries.
- They diversified trade routes and moved settlements to more water-secure areas.
- Governance Strain: Reduced food supply and weak political structures combined with climatic pressures, pushing society toward decline and fragmentation.
- De-urbanisation: The final century-long drought (3531–3418 BCE) coincides with archaeological evidence of large cities being abandoned and populations dispersing into smaller rural clusters.
Theories of Decline of the Indus Valley Civilization
| Natural Disaster Theory |
Floods as a Cause:
- Some scholars argue that major floods may have contributed to the destruction and collapse of urban centres in the Indus Valley.
- Evidence supporting this view includes:
- New houses constructed on top of silt-covered debris, indicating rebuilding after flood damage.
- Houses and streets buried under silt as deep as 30 feet above ground level.
Earthquakes as a Contributing Factor:
- The Indus region lies in a tectonically active earthquake zone, leading to the possibility that earthquakes altered the landscape.
- Earthquakes may have raised floodplains, blocking the natural flow of rivers to the sea and forcing water into urban areas.
|
| River Course Shift |
- It is proposed that the Indus River may have shifted away from major cities, causing water scarcity and reducing agricultural sustainability.
- Such a shift would have made it difficult for cities to survive.
- Evidence: The presence of wind-blown sand and silt in Harappa, might be blown in by the winds
|
| Climate Change Theory |
- Some scholars attribute the decline to climatic deterioration, including rising aridity and the drying up of the Ghaggar–Hakra river system (identified with the ancient Saraswati River).
- Increased aridity in the mid–2nd millennium BCE would have severely affected agriculture in semi-arid Harappan regions.
|
| Aryan Invasion Theory |
- Some early scholars suggested that Harappan cities were attacked and destroyed by Indo-European Aryans, leading to the civilization’s downfall.
- Evidences cited:
- Human skeletons found on streets in Mohenjodaro, interpreted as signs of violent death.
- References in the Rig Veda to the destruction of Dasa fortresses by the god Purandara.
- The theory has been widely rejected by modern archaeology.
|
2 Dec 2025
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