The first argument that I saw (1, 2) was from one David Frawley an American with an Indian title Pandit Vamadeva Shastri supposedly given by a Hindu organization from Mumbai. Incidentally he also sports the title Dr. for his knowledge in Chinese Medicine. He argues for “Indigenous Aryans” meaning that Aryans did not migrate to India from out side but evolved within the present geographical boundaries of India. He further asserts that dark skin color of South Indians is due to excess Sun Light in South India. Then he has to answer as to why certain communities in South are fair skinned? Or why Bhils in North India are dark skinned? Vedic studies is a business for Frawley and he comes handy to Hindutva politics!
The biggest hurdle is the association of Horses with Vedic Aryans and bone analysis shows that horses entered Indus Valley Civilization only around 2000 BC. To over come this difficulty some Hindutva gentle men created fake Indus seals (3) that depict a horse!
There are gentle men who tried to manipulate genetic studies to say that Aryans (Ancient North Indians or ANI in the terminology of Population Genetics) were living in India since 40000 years. Unfortunately the recent genetic studies say (4) otherwise that is the major mix up of ANI with ASI (Ancient South Indians, a population genetics term for Native Indian) took place around 4000 years before the present or around 2000 BC. Also it is being reported that R1a1 gene marker that is found in some Indian castes (5) has originated in East Europe and came to India between 5200 to 2600 years back.
2000 BC is the period when IVC (Indus Valley Civilization) has collapsed. But why some people are so worried about Aryan arrival? They came and settled here long back and so what? Why these attempts to twist and fabricate evidence? We all know that scientific fraud does not stay for long!
 ANI-ASI Admixture Dating, http://www.harappadna.org/