The peaceful unfolding of life of this great ancient civilization was rather abruptly interrupted sometime between 1800 & 1500 B.C.E.The cause may have either been a natural disaster or by an invasion or may be both.
The invading people were known as Aryans.They came from a northwest direction,from the middle-east of Iran & Tajikistan & invaded the subcontinent.The term ‘Aryan’ designated to people who originally belonged to a region somewhere in Eastern Europe perhaps modern Poland & Ukraine.
Aryans were nomadic & pastoral.A warlike & expansionist people,they lived on the spoils of conquest won from the people the subjugated in the course of their migrations.
Features of early Aryans-
Here,we shall compare the salient features of the two civilizations-Indus valley & Aryans.In brief,while the values of Indus valley civilization stressed renunciation,meditation,rebirth,karma & final goal of liberation;the Aryans stressed on ritual sacrifice,loyalty,wealth,this life,progeny,power & heaven.
Thus,it is clear that the sects of religious attitudes ,practices & values professed by these two ancient civilizations of India were almost diametrically opposite to each other.The present Indian society is dominated by the Aryan values.
But there was a brief period of time,perhaps for two-three centuries,in which Aryans began spreading in the east.This was the time when there was merging of these two civilizations.Hence,the values of Aryans today have been more or less influenced from Indus valley civilization.Everyone in our nation including our surrounding nations such as Nepal,Bangladesh,Bhutan,Pakistan belongs to the Aryan race.