Today i came across a very handy website filled with some very interesting articles from genetics.
Genetic Links in the Indus Valley
 

  This month’s feature article explores genetic links in the Indus Valley, the location of the Bronze Age Harappan Civilization. The historical background section includes a discussion of emerging new models of South Asian prehistory. This new research challenges the traditional academic theory of a "Vedic invasion"  from outside of India, and suggests instead local continuity in South Asia dating to the expansion of Neolithic cultures from West Asia.

 The Old Theory (Vedic Invasion): Despite this vivid archaeological record of Harappan life, the
ancient Harappan language (or languages) is unknown, because the Indus Script remains undeciphered.
When the ancient cities of Harappa were excavated, Western archaeologists generally assumed that the
ancient Harappan culture had been replaced by invaders from the Eurasian Steppe and Central Asia at the
end of the Harappan period around 1700-1300 BCE. The new Central Asian invaders were thought to be
the composers of the Rigveda and other Vedic literature written in the Sanskrit language, ancestral to
Hindi and other languages spoken throughout South Asia to the present day.
This “invasion theory” remains the traditional academic model for Indian prehistory, in part
because it explains the similarity of Sanskrit to ancient Greek and Latin. However, archaeologists have
not found clear evidence for a culture from the Eurasian Steppe or Central Asia that influenced South
Asia in the relevant period. The best effort to address this lack of archaeological evidence is currently the
“Kulturkugel” model, in which invaders spread a new Indo-European language without noticeably
impacting the material culture of South Asia. Similarly, linguistic evidence for any pre-Vedic “substrate”
language of the Indus Valley is somewhat limited.

 A New Model (Vedic Harappans): To address this lack of evidence for Vedic invaders from
Central Asia, some scholars are beginning to explore evidence for greater antiquity of the Vedic culture
(dating to the Harappan period) and a South Asian geographical setting for the Rigveda and other texts.
Proposed evidence for the antiquity of Vedic cultures has included astronomical references in
Vedic texts that date to 2,500 BCE and possibly older based on changed star positions (due to the
precession of the equinoxes). Geographical terms in the Rigveda suggest a South Asian setting, including
areas near the Indus Valley and as far east as the lower Ganges. Similarly, river names in the Punjab
suggest the local antiquity of Sanskrit speaking cultures in northern India.2
Most importantly, the Rigveda itself does not mention any migration to northern India. In
contrast, related Zoroastrian texts from Central and West Asia do mention a migration from an earlier
homeland (possibly near the Hindu Kush Mountains). Early evidence from outside of India also includes
West Asian Mitannian and Kassite cultures (contemporary with the Harappan Civilization), which used
Rigvedic like deity names and the peacock (a South Asian animal) as an artistic motif. Taken together,
this suggests the possibility that Vedic cultures were indigenous South Asians (possibly one of several
Harappan cultures), appearing in West Asia through the trade links known to archaeologists.

 The Language Puzzle and Evidence for Early Migrations: A new model of “Vedic
Harappans” would however, create a new puzzle: if there was no Vedic invasion, how did Indo-European
languages find their way to both Europe and South Asia? Archaeological evidence supports two major
expansions into South Asia: (1) a Neolithic expansion (possibly from West Asia) between 6,000-4,500
BCE; and (2) an Iron Age expansion (possibly from Central Asia) between 800-200 BCE.
Neolithic (Pre-Harappan) Expansion: One possibility is that food producing cultures of West
Asia brought Indo-European languages to South Asia during the Neolithic expansion (6,000-4,500 BCE).

 This early date for the languages ancestral to Sanskrit would not contradict the Neolithic date for the
Proto-Indo-European language that has been proposed by some linguists

 It was going nice unill got struck by this funny and idiotic assumption-

 Iron Age (Shakya) Expansion: The second expansion dating to 800-200 BCE has been
associated with Shakya or Saka (Scythian related) cultures from Central Asia that influenced early
Buddhist culture in India. For instance, the Sanskrit scholar Michael Witzel has suggested Central Asian
links for some Shakya customs, such as the use of burial mounds (stupas) and Zoroastrian concepts in
Buddhist literature.
First emerging in Śākyamuni’s native kingdom of Lumbini (in present day Nepal), Buddhism
eventually spread outward from the Indian Subcontinent and flourished in the mercantile Silk Road oasis
settlements of Central Asia. In the context of a “Vedic Harappans” model, these Shakyas might have been
peripheral Harappan or Vedic influenced cultures from Central Asia that returned to the core Vedic
location of India during the Iron Age.

This shakya-saka connection theory is an old one with recently regenerated by Indologists like Michael Witzel but has no real base at all. Now just see the vital conclusion-

 Both STR and SNP based analyses indicated substantial genetic links between the Indus Valley
and both the interior of the Indian Subcontinent and West Asia. Archaeological evidence for a population
expansion (possibly from West Asia) between 6,000 and 4,500 BCE might relate to genetic links with the
Mesopotamian region (STR) and Caucasus-Anatolian region (SNP). Expansions of food producing
cultures during this period might have provided an opportunity for the Indo-European languages
(ancestral to Vedic Sanskrit) to reach the Indian Subcontinent.
In contrast, genetic links with Siberian populations were smaller. These included relatively small
Altaian (STR), Baltic-Urals (SNP), and Mongolian (SNP) genetic components. These genetic links might
express later and less extensive population expansions from the Eurasian Steppe and Central Asia, such as
possible Shakya migrations during the Iron Age.
In addition, results also suggested genetic expansions from India to Central Asia. This included
South India components identified in Kalash, Tajik, and Turkmen populations near the periphery of the
Indus Valley region. These genetic links might express population expansions from South Asia, such as
during the period of the Bronze Age Harappan Civilization. Future research might explore South Asian
genetic links in more distant locations (such as the BMAC and Urals), where evidence for Vedic
influences in material culture have been suggested by archaeologists.
In summary, results are consistent with emerging alternative models of South Asian prehistory, in
which the Vedic cultures were descended from indigenous Harappans already resident in South Asia.
Rather than a putative “Indo-European invasion” from Central Asia in the late Bronze Age, results
suggest the possibility of an earlier and more peaceful “Indo-European diffusion” of food producing
cultures from West Asia during the Copper Age.

yog

 My conclusion:

Atleast the age of Indo-European language here is getting older which i think is correct and yes Rikved should be pushed 6-5 centuries deeper than its current date of around 1700-1100 B.C.

  About the 800 B.C. intrusion( should be close to 600b.c. instead of 800b.c. See the BMAC post link) i think they were related to the Parthians or to the  Dasa-Dasyu people mentioned frequently in the Rikved  rather than the saka people.

As we should know the scythian related people started to venture here only from the middle 2nd century b.c.

We should also remember that Chandragupta  with the help of his teacher Chanakya  aka Vishnu Gupta aka kautilya  estabilished an unified Indian empire the legacy of which lasted  untill 185 B.C. starting from 322B.C. so i don't see  much of intrusional admixtures happening during that period!

so the 800-200 b.c. idea is not that promising at all.

And at the last the age of the components is more vital than the proportion on certain populations.