Origin of The Vedic Civilization: Native Aryans or Aryan Invasion?

Hinduism, whose basis is mainly the Vedas, originated in the Indus-Saraswati basin. But the origin of the people who wrote the Vedas, or the ancient Aryans, is hard to say.

There are three different theories:
1. The ancient Aryans migrated to India wiping out the Indus Valley Civilization (IVC) and brought their religion to the subcontinent.
2 The IVC was wiped out due to natural calamities some time during 1500 BC. The Aryan Migration happened much later.
3. The Aryans were native to India and the Vedic religion originated here.

The problem with all these theories is the lack of archaeological and contradicting literary(mainly the Vedas, which has a lot of description of the geography and the culture of the subcontinent) and other evidences . Let's look these theories, in detail, along with the evidences supporting and contradicting them:

Theory 1 & 2: Archaeologists have found a lot of evidence to support the existence of the IVC which flourished along the banks of river Indus around 3000 BC - 1500 BC. However, they haven't found any archaeological evidence which can point towards the reasons for it's decline. There is also no evidence of an Aryan invasion. The Aryan invasion theory is based entirely on comparative philology.  However, one thing is certain from the archaeological evidences i.e. the Indus valley civilization did exist and it was quite different from Vedic civilization. All the archaeological evidences in hand, suggest that the Indus valley people and the Vedic people never came into contact. But, there is also no evidence of a Vedic civilization as such. In other words, most of the archaeological data that we have is either related to IVC or to the period after the start of Mauryan Dynasty (the timing of which is also debatable but is widely accepted to be around 350 BC), by which time the Vedic religion was mature and strongly assimilated into the society. So one cannot derive the origin of the Vedic religion or it's originators i.e. the Aryans, just based on just archaeology. Also note that the Vedas claim that the Vedic people are natives of India and there is no mention of any migration, neither do they hint the existence or ruins of any other civilization similar to that of IVC.

Theory 3: This is the most favorable theory based on literary, geological, genetic and astronomical evidences but lacks major archaeological support.

Geological and literary evidences:
Vedas regard the river Saraswati to be the most important one, even more than Indus. However, it doesn't exist anymore as it dried up long time ago. It was the mightiest river during the Vedic times, with some hymns of Rigveda even mentioning that at one place the river stretched 14 kms wide. This river, if you go by literary evidence, began to dry up during the time of Mahabharata  Geologists have confirmed, using satellite imagery, that this river did exist in almost the same location as mentioned by the Vedas, and dried up completely around 1900 BC. This literary and geological evidence creates a lot of controversy as it suggests that the Vedas originated much before 1900 BC. Also, there have been significant discoveries of ruins of ancient cities that existed on the banks of this rivers.

Astronomical evidences:
Ancient Aryans were intensely fascinated with the celestial objects. Most of the literary works have a lot of mentions of planets, stars, and other celestial events. Prof. Narahari Achar, a famous astrophysicist from University of Memphis, simulated the celestial events mentioned in the Mahabharata and placed it's time around 3000 BC. Just for the sake of argument, if Mahabharata was indeed true and if it happened around that time then this puts the Vedic civilization and the Vedas much more behind in the history.

Genetic Evidences:
Some of the studies conducted by highly notable people in this field: Oppenheimer (2003), Cavalli-Sforza et. al.(2003), Sahoo et al.(2006) etc suggest that there was a migration out of India, rather than into India. Sahoo even goes on to state that : "It is not necessary, based on the current evidence, to look beyond South Asia for the origins of the paternal heritage of the majority of Indians at the time of the onset of settled agriculture. The perennial concept of people, language, and agriculture arriving to India together through the northwest corridor does not hold up to close scrutiny. Recent claims for a linkage of haplogroups J2, L, R1a, and R2 with a contemporaneous origin for the majority of the Indian castes’ paternal lineages from outside the subcontinent are rejected, although our findings do support a local origin of haplogroups F* and H. Of the others, only J2 indicates an unambiguous recent external contribution, from West Asia rather than Central Asia."

Conclusion:
The Vedic religion originated in the Indus Saraswati basin but the origin of the people who created this religion and time of creation is highly debatable. The archaeological evidence can only prove the existence of Indus Valley Civilization and cities on the banks of river Saraswati, but it can neither prove the Aryan Invasion theory nor the connection of Vedic and Indus civilization. One can only speculate the invasion/migration of the Aryans based on comparative philology. However, some of the more recent genetic studies indicate that there was indeed a migration but not into India, but out of India. The literary evidences and recent geological studies indicate that the river Saraswati did exist and dried up around 1900 BC suggesting that the Vedas originated much before 1900 BC.

I leave it up to the reader to decide whether the Aryans were native to India or migrated from the Central Asia, and the time of composition of the Vedas.

References:

Puri (2001) : Origin and course of Vedic Sarasvati River in Himalaya, Geo. Survey of India.

Tripathi, Bock, Rajamani, Eisenhauer (2004):Is River Ghaggar, Saraswati? Geochemical constraints, Current Science Vol 87. No. 8 :

http://www.iisc.ernet.in/~currsci/oct252004/1141.pdf

Frawley David, Science of the sacred, 2010:

http://gosai.com/sites/gosai/files/books/science-of-sacred-2010.pdf

Achar Narahari(2003), Date of the Mahabharata War based on Simulations using Planetarium Software.:

http://www.omilosmeleton.gr/pdf/en/indology/narahari01.pdf

Sahoo. et al. (2006), A prehistory of Indian Y chromosomes: Evaluating demic diffusion scenarios, PNAS: http://www.pnas.org/content/103/4/843.full

Cavalli-Sforza et al. (2003), Application of molecular genetic approaches to the study of human evolution, Nature Genetics: http://www.facstaff.bucknell.edu/sdjordan/PDFs/Cavalli%20Sforza%202003%20Nat%20Gen.pdf

Oppenheimer, Stephen (2003): The Real Eve: Modern mans journey out of Africa.

Griffith Ralph, Translation of Rig Veda:

http://www.sacred-texts.com/hin/rigveda/