<P> Around 1800 BCE signs of a gradual decline began to emerge, and by around 1700 BCE most of the cities had been abandoned . Recent examination of human skeletons from the site of Harappa has demonstrated that the end of the Indus civilisation saw an increase in inter-personal violence and in infectious diseases like leprosy and tuberculosis . </P> <P> In 1953 Sir Mortimer Wheeler proposed that the invasion of an Indo - European tribe from Central Asia, the "Aryans", caused the decline of the Indus Civilisation . As evidence, he cited a group of 37 skeletons found in various parts of Mohenjo - daro, and passages in the Vedas referring to battles and forts . However, scholars soon started to reject Wheeler's theory, since the skeletons belonged to a period after the city's abandonment and none were found near the citadel . Subsequent examinations of the skeletons by Kenneth Kennedy in 1994 showed that the marks on the skulls were caused by erosion, and not by violence . </P> <P> Suggested contributory causes for the localisation of the IVC include changes in the course of the river, and climate change that is also signalled for the neighbouring areas of the Middle East . As of 2016 many scholars believe that drought and a decline in trade with Egypt and Mesopotamia caused the collapse of the Indus Civilisation . </P> <P> The Ghaggar - Hakra system was rain - fed, and water - supply depended on the monsoons . The Indus Valley climate grew significantly cooler and drier from about 1800 BCE, linked to a general weakening of the monsoon at that time . The Indian monsoon declined and aridity increased, with the Ghaggar - Hakra retracting its reach towards the foothills of the Himalaya, leading to erratic and less extensive floods that made inundation agriculture less sustainable . </P>

What led to the end of indus valley civilization