An Aryan Invasion dated back to 1500 BC was proposed by Max Muller in colonial period intentionally or unintentionally with no archeological or scientific basis and purely on linguistic basis. Problem with linguistic basis is that it was speculative and based on extrapolation from time of Buddha (500 bc) based on stages of development of vedas, considering 200 years at every stage. While it can be said to be good start in Indian historiography when little was known about Indian past. But problem was such a vague prediction was considered to be a universal truth and even after discovery of harrapan sites, it was fitted in old theory instead of questioning the Aryan Invasion theory.
Selective reading of Vedas and Purana/Upanishad resulted into interpretation of war mentioned between deva and asurs as between attackers from Central Asia and indigenous people. When more sites were discovered as far as Rakhigarhi in Haryana and lothal in Gujrat, Aryan invasion theory was rejected by most of historian in favour of Aryan immigration. Aryan Invasion theory was developed in period of colonization and in this period all other cultures other than European was considered as lower to the European Greek/Rome culture and race was a central idea. Aryan invasion was used to justify English invasion on India. Part of this misinterpretation was because of background of historians who belonged to the monolithic culture and were unable to understand the plurality of past civilizations (Indian, Mesopotamian) and coherent existence of many ideas within same society was alien to them. So they tried to divide Indian society where Aryans had language Sanskrit and had Vedic culture that contradicted with indigenous Indian culture and in war that followed Aryan were able to subjugate the indigenous. Also reading of spiritual text with material angle resulted in vague interpretation .For reason unknown (may be fear of creation of majority identity assertion) left historian continued the colonial proposed theory, instead of drawing more logical conclusion. But in this process they denied even the well known facts. From ancient knowledge of astronomy to various mathematical and scientific discoveries all were discarded as myth. And Indian ancient discoverers/inventors were never given their due place. From Yoga to knowledge of Vedas they were accepted in India only after west recognized them as important knowledge.
Crucial part ignored in this whole Aryan Invasion/immigration theory is Sarswati River. Earlier denied as a mystical river now more proof are coming of its existence and subsequently drying up or changing the course. Rivers can change course due to many reasons. As recent as in 1950 Brahmaputra changed its course. Sarswati is said to be a present day Ghaghar river. Presence of river Sarswati seems plausible as many big archeological sites are found in areas that are presently desert or dried, while its highly improbable scenario because all historical civilizations were developed on river banks. And these sites were not peripheral sites; in fact Rakhigarhi of Haryana is bigger than Mohenjo-Daro and Harappa. Many scholars today both in India and the West, have proposed in wake of this that that the Harappan or Indus Valley civilization, should be renamed the Rakhigarhi or Sarasvati civilization. Change of course of river can be predicted from ancient text also, as in popular culture Ganga-Yamuna confluence in Allahabad is known as Triveni sangam of Ganga, Yamuna and Sarswati. A story is also popular that Sarswati in Prayag dried due to “Shraap” of Maa Sita. So it is highly possible that somewhere between 2000-1000 BC Sarswati changed its course and instead of Arabian Sea moved towards Bay of Bengal and later dried. This sudden shift in course may resulted in slow migration of people from Indus water system to Ganga-Yamuna river system as the fertile land along the Sarswati was now unsuitable for agriculture and situation of drought developed. Often question is raised about degradation of civilization from Indus Urban system to primitive Ganga Yamuna civilization. But one must remember that urban civilizations flourish when there is excess food produce and some people are free to take other activities of art and trade. In such a large scale migration to totally new place, agricultural land will have to be developed by clearing forests, developing canal systems, rearing animals. This will surely take time and labour. Thats why in this period large scale urban cities were not seen and instead small urban centres like Dwarka were developed. Also one must simultaneously study socio –political development in Middle East with whom Indus valley people traded that may have resulted in decline of trade with them and thus rendered creation of large urban centre for trade futile.
With these new developments it is better that self-contradicting Aryan–Invasion/immigration theory must be discarded and it should be studied with fresh approach with simultaneously taking into account literary and archeological evidences.