Who proposed the theory that Harappan Civilization declined due to Aryan invasion?

The Harappan Civilization, also known as the Indus Valley Civilization, was one of the world's earliest urban civilizations. It flourished from approximately 2600 BCE to 1900 BCE in the Indus River valley. Major cities include Harappa (Punjab, Pakistan), Mohenjo-daro (Sindh, Pakistan), Lothal (Gujarat, India), and Dholavira (Gujarat, India).

Harappan civilization had advanced town planning: grid-pattern streets, two-story brick houses, well-planned drainage system (most advanced in ancient world), granaries, and public baths. The Great Bath at Mohenjo-daro was approximately 12m x 7m and is considered a ritual bathing area. Town planning is a key feature asked in UPSC and SSC exams.

Harappan people engaged in agriculture (wheat, barley, cotton), animal husbandry, crafts (pottery, bead-making, metallurgy), and trade. They had extensive trade with Mesopotamia as evidenced by seals found in both regions. Lothal had a dockyard suggesting maritime trade. They used standard weights and measures showing organized commerce.

The Harappan script was a pictographic writing system with about 400 signs. It is written from right to left. The script has NOT been deciphered yet, making Harappan civilization one of the few ancient civilizations whose language remains unknown. This undeciphered script is a frequently asked fact in UPSC and SSC competitive exams.

The decline of Harappan Civilization around 1900-1500 BCE is attributed to multiple theories: climate change and drying of the ancient Saraswati River leading to droughts, floods and waterlogging, soil exhaustion, and disruption of trade networks. The collapse was gradual, not sudden, shown by declining civic standards in smaller settlements.