Though there are various theories, the exact reason is still unknown. As per a recent study by IIT Kharagpur and Archaeological Survey of India, a weaker monsoon might have been the cause of the decline of Indus Valley Civilization. Environmental changes, coupled with a loss of power of rulers (central administration) of Indus valley to sustain the city life might be the cause (Fariservis Theory). There might be a resource shortage to sustain the population, and then people moved towards south India. Another theory by Dr Gwen Robbins Schug states that inter-personal violence, infectious diseases and climate change had played a major role in the demise of the Indus Valley Civilization.