I do not intend to question the genetics findings of the Vagheesh et al paper because I am not a genetics researcher and I have myself not gone through all the details of the paper to critique its methodology. Obviously as in all science, the paper will get validated or rebutted via future papers from other researchers.
So I start with tacit acceptance of the finding of steppe genes as a marker for Indians.
My only point of contention is whether the steppe migrants implied in the paper carried Indo-European languages with them to India. I am in no way questioning the migration-language connection between steppe and Europe as made in the paper. But similarity between steppe migration to Europe and to India does not mean that IE languages first arrived in India with this wave of migrants. I believe that it is not sufficient to claim this particular migration to India as a source of IE in India
There are two important preconditions to make a claim that people from place A took their language to place B and introduced that language for the first time in place B. First there must be incontrovertible evidence that the migrants from place A actually used to speak the language that they took to place B in the pre-historic era that they migrated. Second, there must be evidence that the language they carried with them did not already exist in the "place B" to which they migrated. Anything less is conjecture. Not science. I will take these two points in reverse order.
Any migration carrying IE language to India for the first time has to be shown to have occurred before 2500 BCE because there is powerful evidence of IE language having been in India by 2500 BCE and most likely for millennia prior to that. I will try and be as brief as possible about the evidence which in detail is enough to fill a book chapter.
The evidence for IE in India prior to 2500 BCE falls under 2 main heads
2. Records of hydronyms, toponyms and climate related events
I am only going to deal with the latter
The presence of Vedic Sanskrit in India was attested in text form as recently as 150 AD or so and if attestation is the metric then all talk of Sanskrit as an ancient language is moot. However it was dubbed as ancient by Max Muller who surmised that the post Vedic texts were contemporaneous with the Buddha who was thought to have lived around 600 BC. Muller then worked backwards, assuming about 200 years for the composition of each class of post Vedic and Vedic texts and arrived at a date of 1200 to 1000 BC for the Rig Veda. However many factors have called these "guesstimated" dates into question.
1. Rig Veda 7.95.2 speaks of a mighty river called the Saraswati flowing from mountains to the sea (RL Kashyap, Rig Veda Samhita, Mandala 10, Sakshi trust 2012)
2. More information about the location of the "Saraswati" comes from Macdonell & Keith "Vedic Index of names and Subjects" 1912: In the enumeration of rivers (evidently from east to west) in Rv. x. 75, 5, Ganga, Yamuna, Sarasvati, Sutudri, the Sarasvati comes between the Jumna and the Sutlej, the position of the modern Sarsuti (SaraswatI). which, flowing to the west of Thanesar, is joined in Patiala territory "
These passages give a rough idea of some ancient river, real or imagined, called the Saraswati that was situated between the Yamuna river (that passes through Delhi) in the east and the Sutlej river in the west
3.Still more geographical information comes from Macdonell and Keith:
a. Madhyadesa, the ‘Middle Country,' is, according to the Manava Dharma Sastra, the land between the Himalaya in the north, the Vindhya in the south, Vinasana in the west, and Prayaga (now Allahabad) in the east that is, between the place where the Sarasvati disappears in the desert, and the point of the confluence of the Yamuna (Jumna) and the Ganga (Ganges)
b. The Baudhayana Dharma Sutra defines Aryavarta as the land east of Vinasana ; west of the Kalakavana, ‘ Black Forest,' or rather Kanakhala, near Hardvar; south of the Himalaya; and north of the Pariyatra or the Paripatra Mountains.
c. Vinasana, 'disappearance,' is the name of the place where the Sarasvati is lost in the sands of the desert.
Here we have references to "Vinasana" a place where a "Saraswati river" disappears in the desert. This information comes from post-Vedic texts - most likely composed centuries after the Vedas. The Himalayas in the north are mentioned. In the south are the Vindhya mountains, the traditional barrier between north and south India. The Paripatra mountains are the westernmost reaches of the Vindhyas. To the east is the Yamuna river which corresponds to what the Vedas record as being to the east of the Saraswati. West of that is the place where the Saraswati "disappears in the desert"
So here we have mention of a river that does not exist today but located in a recognizable geographic location. The Vedas call it a mighty river that reaches the sea and later texts claim that the river dries up in the desert
4.Now we come to more recent events and discoveries. To a man called RD Oldham must go the credit for identifying the site in the Rajasthan desert that was apparently the ancient Saraswati river. However it was his compatriot - a similarly named CF Oldham who wrote:
“..local legends assert ( that Sarasvati ) once flowed through the desert to the sea . In confirmation of these traditions , the channel referred to , which is called Hakra or Sotra , can be traced through the Bikanir and Bhawulpur states into Sind , and thence onwards to the Rann of Kach . . . attested by the ruins everywhere overspread what is now an arid sandy waste . Throughout this tract are scattered mounds , marking the sites of cities and towns . And there are strongholds still remaining... Amongst these ruins are found, not only the huge bricks used by the Hindus in the remote past , but others of a much later make..”
5. Next it was a British geologist called Aurel Stein who wrote, in 1942, a monograph entitled “A survey of ancient sites along the`lost' Sarasvati River” in which he identified the Ghaggar river in north India as the remnant of the Saraswati, and said that for over a distance of 100 miles (160 km) the river bed of the Ghaggar is more than 2 miles (3.2 km) wide and in many places over 4 miles (6.4 km) wide. He noted the scanty flow in the modern Ghaggar and wide ancient river bed meant that there had been a much mightier river in the remote past. Aurel Stein also noted findings of ancient settlements by the sides of this old Saraswati river bed that he connected up with the Indus Valley civilization.
6. There is no doubt that a river existed in the site of the Saraswati as noted in old texts. But was it a mighty river that reached the sea? For that I refer you to a 2017 paper that has done isotopic analyses of cores from the Rann of Kutch.
Tracing the Vedic Saraswati River in the Great Rann of Kachchh, Nitesh Khonde, Sunil Kumar Singh , D. M. Maurya , Vinai K. Rai , L. S. Chamyal &
Liviu Giosan https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5511136/
This study shows that until 10,000 ybp (8000 BCE) there was a great river in that area that drained into the sea. Progressive drying started after that but the paper states that their method would not be able to detect how long the river flowed all the way to the sea after that
7. Another paper: Adaptation and human migration, and evidence of agriculture coincident with changes in the Indian summer monsoon during the Holocene Anil K. Gupta , David M. Anderson , Deep N. Pandey and Ashok K. Singhvi. http://repository.ias.ac.in/21932/
This paper documents a massive in crease in rainfall over the entire Indian subcontinent from 10000 ypb to 7000 ybp (8000 - 5000 BCE) and mentions the effect this had on crops in Mehrgarh. Aridity started increasing after 5000 ybp.
So what are the facts we have? The Vedas mention a mighty Saraswati river that reached the sea. Later texts clarify its location but observe that it dries up in the desert. That location correlates perfectly with the finding of a massive river bed with IVC settlements alongside. Modern isotopic studies, palaeoclimatology and palynological studies indicate a mighty river in that location, which flowed into the sea up to 8000 BCE and possibly for a little longer. Heavy monsoons swelled subcontinental rivers from 8000 BCE to 5000 BCE. Aridification started after that. These facts correspond well with the ancient records that survived in the Vedas and post-Veda texts.
All the ancient records of events and geography, ostensibly from 8000 BCE are preserved in an "Indo-European language". That language, by the estimate of Indologist-Philologists has 96% IE words with minimal substrate of any other language. No other IE language to my knowledge has such a large proportion of IE derived words.
The pointers towards a very ancient presence of IE language in India, long before influx of the steppe people described in this paper is strong. In a separate post I will deal with the alleged area of origin of IE language coming to India, the steppe region.