The archaeologists had to depend on various stray materials and evidences to determine the origin of Harappan Civilization.
The comparative analysis of the ruins found at different places of the Indus valley and Mesopotamia gives us an account of origin and Extent of Harappa Civilization.
Some archaeologists are of opinion that the date of Indus Valley Civilization was between 3250 B.C. and 2750 B.C. But some recent discoveries have led the archaeologists and the historians to advance the timeline of Indus Valley civilization. In their opinion, it was not prior to the period between 2400 B.C. and 1800 B.C. that India and Mesopotamia did come in contact with each other.
Further, documents found at Akkad, (situated in the north-east of ancient Mesopotamia) point to the commercial relations they established With the Indus people. The Indus cities had their highest development in the period between the third and second millennia B.C. India had at that time carried on efficient trade with foreign lands.
Again, a similarity between the earthen containers of Clossus of Crete and those of Harappa has been discovered. This made time scholars assume that Harappan civilization lasted at least till sixteenth century B.C. In other words, the Harappan culture extended over a period between 3000 B.C. and 1600 B.C.