Question

Discuss the reasons for the Downfall of the Harappan Civilization.

Answer 1

Step 1: Environmental/climatic theories:
A major reason proposed is climate change -- weakening monsoons and increasing aridity over the Indus region -- which reduced agricultural surplus needed to sustain large cities.

Step 2: Hydrological/tectonic theories:
Tectonic shifts are believed to have altered river courses: the Ghaggar-Hakra (identified by many with the Saraswati) is thought to have dried up, while the Indus possibly changed course and caused destructive flooding at sites like Mohenjodaro.

Step 3: Aryan invasion theory (and its rejection):
An older theory attributed the decline to invasions by Indo-Aryan-speaking peoples, based on skeletal evidence at Mohenjodaro; most modern historians now reject an 'invasion' as the primary cause, citing lack of conclusive archaeological/genetic support for a violent conquest.

Step 4: Economic and internal factors:
Decline of long-distance trade with Mesopotamia, overexploitation of land and deforestation, and possible administrative/social breakdown of the standardised urban system are also cited.

Step 5: Conclusion:
Most historians today favour a combination of factors -- gradual climatic and river-course change leading to declining agriculture and trade, causing progressive de-urbanisation -- rather than a single sudden catastrophe or invasion.

Final Answer:
\[ \boxed{\text{A combination of climate change, river-course shifts (drying Ghaggar-Hakra), declining trade and agriculture -- not a sudden Aryan invasion -- caused the gradual decline}} \]