I shall interpolate (in a way) a theory concerning the time of the Mahabharata War (5561 BC) and the rise of Cain, otherwise known as Sargon of Akkad, around 3800 BC.
If it is true that the Yamuna and Ganges Aryans (Pandavas) fought the natives (led by the Kauravas) in the 6th millennium BC--and that horrifically destructive weapons were used in the "Great Rebellion"--then Bharata became a devastated land.
Let's move some one thousand and five hundred years up to 4004 BC, the date that Yahweh Elohim formed the man (Adam) for a living soul--and taking some of Adam's DNA to form Eve. India was then given an ample amount of time to recover--a seemingly interminable period of darkness that slowly saw things return to normal. I've heard that Baghdad didn't recover from its pillage by the Mongols (in terms of population) until the time of Saddam Hussein. That's about seven hundred years; just imagine the aftermath of the Mahabharata war, if it took over 1,500 years for India to recover from that.
Cain, whose father was Satan (Heylel), was born some time after 4004 BC. He came to prominence circa 3800 BC in the land of Nod (modern Iraq). He proceeded to build the First Babylonian Empire, entering history as Sargon.
Sargon concentrated his efforts in the west. He reached the Mediterranean and established Knossos (Gnosis) on Crete. It is interesting that he did not move towards the east: perhaps Bharata was still recuperating from the war of Great Bharata: Sargon did not find that area attractive and so only had some (indirect) involvement there.
Another apparent piece of evidence that supports an earlier date for this war would be that China is conspicuously missing from the account of the Great Rebellion. That's because no nation by that name existed in the 6th millennium. (The Mahabharata names all the neighbors of the epic Aryans immediately north of the Himalayas.)
China was founded by Cain in the 4th millennium. Thus Cain, as far as the east was concerned, sailed to the land that would become known as "China," bypassing India.
(I speak of the Epic (Yamuna and Ganges) Aryans--as opposed to the Vedic Aryans to the west (who authored the older (for the most part) Rig Vedas. It was the Vedic Aryans who fought the Battle of the Prusni (Ravi) River. The Vratyas may have been even older Aryans (Aryas or Iranians) who, before they entered India (as conquerors) from Tibet, pledged an oath to each other.)