What was the reason of extinction of the Indus Valley and Harappan civilization?

The extinction of the Indus Valley Civilization, also known as the Harappan Civilization, is a topic of ongoing debate among scholars. Several factors are believed to have contributed to its decline, which occurred around 1800 BCE. Here are some of the key reasons:

Causes of Decline

1. Climate Change and Environmental Factors:

   • Decrease in Monsoons: A significant reduction in summer monsoons around 2500 BCE led to droughts, making agriculture difficult for a society heavily reliant on river floods for irrigation1.
   • Drying of the Saraswati River: The progressive decrease in water flow along the Saraswati River system, possibly due to tectonic activity in the Himalayas, affected agricultural production and settlement viability25.
   • River Course Changes: Shifts in river courses, such as the Hakra River, led to desertification and abandonment of settlements4.

2. Geological Events:

   • Tectonic uplift and earthquakes disrupted trade networks and caused the displacement of seaports, further destabilizing the civilization4.

3. Human Activities and External Pressures:

   • Invasions and Trade Disruptions: Although the theory of Aryan invasions is now largely discredited, external pressures and disruptions to trade networks may have played a role34.
   • Epidemics: Urban conditions may have facilitated the spread of diseases like malaria and cholera, weakening the civilization's administrative structures5.

4. Societal and Administrative Factors:

   • The lack of strong centralized institutions and potential internal conflicts could have contributed to the civilization's transformation and eventual decline5.

Conclusion

The decline of the Indus Valley Civilization likely resulted from a combination of these factors rather than a single cause. The civilization did not disappear suddenly but transformed over time, with many of its cultural elements continuing in later societies45.