Various causes have been suggested for the decline of Harappan culture. Consider the causes mentioned below and identify the weakest of them.

The decline of the Harappan culture is attributed to various factors, primarily environmental and geographical. Historians cite constant naturally occurring floods [4], shifts in the course of the Indus River leading to inundation or drying [4], and soil salinity resulting from overuse of the landscape [4]. While Sir Mortimer Wheeler once proposed the 'Aryan Invasion' theory, it is now considered the weakest explanation. Archaeological evidence shows that the Aryans migrated to India around 1500 BCE [2], which is significantly later than the start of the Harappan decline around 1900 BCE [3]. Furthermore, there is a lack of skeletal evidence or destruction layers to support a large-scale massacre or invasion [2]. Modern scholarship emphasizes a gradual transformation and migration toward the east and south due to climate change and ecological degradation rather than a sudden external conquest [3].

Sources

1. [1] History , class XI (Tamilnadu state board 2024 ed.) > Chapter 1: Early India: From the Beginnings to the Indus Civilisation > Decline > p. 14
2. [4] THEMES IN INDIAN HISTORY PART I, History CLASS XII (NCERT 2025 ed.) > Chapter 1: Bricks, Beads and Bones > 9. The End of the Civilisation > p. 17
3. [2] History , class XI (Tamilnadu state board 2024 ed.) > Chapter 2: Early India: The Chalcolithic, Megalithic, Iron Age and Vedic Cultures > SUMMARY > p. 31
4. [3] THEMES IN INDIAN HISTORY PART I, History CLASS XII (NCERT 2025 ed.) > Chapter 1: Bricks, Beads and Bones > Terminologies, Places and Time > p. 1