The Civilization of the Indus Valley was in the Copper Age preceding the Iron Age. Archeological evidence points to the Indus Valley Civilization’s upper date limit in around 3000 B.C. And Sir Mortimer Wheeler set the lower limit around 1500 B.C. based on archaeological data and the Rig Veda date. So, the Indus Valley Civilization may have dated from 3000 B.C. and lasted until 1500 B.C.
The causes of decay: the end of the civilization of the Indus valley:
It is very difficult to discern the causes of the decay of this culture at the present state of our understanding. Based on the available information, however, some efforts may be made to figure out the causes of the decline of Indus Valley civilization.
(1) Climate change and human migration: It is known from estimates of animals such as rhinoceros, elephants, tigers, etc., that the valley in Indus had more rains and that the land was swampy with jungles. But the amount of rainfall declined over time, and the valley became a desert. So people fled from the region under the teeth of this inhospitable environment.
(2) Deforestation and neglect in order to protect dams: excessive deforestation by tree felling’s and poor preservation of dams and irregularities, and a drop in agriculture are some reasons that have contributed to the land being destroyed.
(3) Degeneration of Civic Standard: in later phases of Indus Valley civilization, there is a pronounced degeneration of municipal standard. In all appearances, cities appear in the forms of decay like abandoned towns.
(4) Influence of the Indus Flood: there was definitely an increasing danger of an Indus flood causing decay. The catastrophic floods washed over the city at least three times. From the excavations, the houses have been built and established to prevent the risk of flooding.
(5) External invasions as the ultimate factor: the ultimate extinction of the Indus Valley civilization is due to the invasion of people, possibly Aries, from the outside. The disastrous end of Indus civilization came approximately 1500 B.C. when the Aryans invaded the Land of the Seven Rivers.
(6) Circumstantial proof: There is also some circumstantial evidence to support the Aryan invasion theory. And the Aryans were accused of destruction of the Indus Valley or Harappa civilization in the light of the chronology.