What led to the decline of the Harappan civilization?

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Dear student, ● Several contesting theories are related to the decline of Harappan civilization: ◇Some scholars hold that they were destroyed by invading barbaric tribes. Such theories of a violent end, have been partly proved by the discovery in Mohenjodaro of human remains that indicated a violent cause of death. Evidences were not consistent with the above theory as most other cities showed an absence of a massacre. Then there are theories of climatic factors like flooding of plains and cities; or the shift in the course of River Indus.