What is the Sarasvati river mentioned in the Vedas?

There has been much discussion about the Ghaggar-Hakra and its relation to the Saraswati river mentioned in the Rig Veda.  The Saraswati is mentioned in every mandala of the Rig Veda except the fourth. The subject matter in RV 6.61,  7.95 and 7.96 is entirely devoted to Saraswathi. The majority of Indus settlements that have been excavated has been along the Ghaggar-Hakra river rather than along the Indus. 

RV 7.95.2 says,  “Sarasvati, chief and pure of rivers, flowing from the mountains to the ocean, understood the request of Nahuṣa, and distributing riches among the many existing beings, milked for him butter and water.”

 It is believed that the Ghaggar was a tributary of the Sutlej and the Yamuna in the pre-Harappan era about 8000 years ago.  Geological changes caused the Sutlej to change course and move west to join the Indus. The Yamuna changed course and moved east to join the Ganga. By the second millennium, the Ghaggar was no longer a perennial river but depended on monsoon rains. 

In the earlier books of the RV, the Sarasvati is called naditame (the best of the rivers), which surpasses in majesty all the other rivers, is fierce, comes down with a tempestuous roar etc.  Later Vedic texts say that the Sarasvati disappears in the desert in a place called Vinasana. 

Rajesh Kochhar believes that the earlier mandalas refer to a river that he calls Naditame Sarasvati while the later mandalas and post Vedic literature which says that the Sarasvati disappeared in the desert refers to another river which he calls Vinasana Sarasvati. 

It is possible that the Saraswati of the earlier mandalas refers to the Haraxvati river, now known as Helmand in Afghanistan. There is a similarity between the description of Haraxvati in the Yasht (hymns in Zoroastrianism) in Avestan language and the description of Sarasvati in the Rig Veda. Rajesh Kochhar describes the similarity in detail. 

Noted historian Romila Thapar notes that the description of the Sarasvati shown above does not agree with the fact that the Ghaggar does not flow from the mountains into the sea

There is also a belief that Sarasvati flows underground and joins the Ganga and Yamuna at Prayagraj at Triveni Sangam. At Sirsa, Haryana, the Ghaggar flows south-west into Rajasthan. Prayagraj is over 900 kms to the south-east of Sirsa.

However it is not clear why the Rig Veda would describe a river that is about 1000 kms to the west of the Ghaggar-Hakra river where the Vedas may have been composed.

What is the Nasadiya Sukta?

The Nasadiya Sukta  is a hymn in the Rig Veda. It is famous for the questions it asks about the origin of our  Universe. 
It is in RV 10.129 

For example RV 10.129.6 says -

The gods themselves are later than creation,
so who knows truly whence it has arisen?

This is in contrast to the belief in most religions that God created the Universe.

Given below are the verses from the Nasadiya Sukta and their English translation.

10.129.1
नास॑दासी॒न्नो सदा॑सीत्त॒दानीं॒ नासी॒द्रजो॒ नो व्यो॑मा प॒रो यत् ।
किमाव॑रीवः॒ कुह॒ कस्य॒ शर्म॒न्नंभः॒ किमा॑सी॒द्गह॑नं गभी॒रं ॥

Then even nothingness was not, nor existence,
There was no air then, nor the heavens beyond it.
What covered it? Where was it? In whose keeping
Was there then cosmic water, in depths unfathomed?

10.129.2
न मृ॒त्युरा॑सीद॒मृतं॒ न तर्हि॒ न रात्र्या॒ अह्न॑ आसीत्प्रके॒तः ।
आनी॑दवा॒तं स्व॒धया॒ तदेकं॒ तस्मा॑द्धा॒न्यन्न प॒रः किं च॒नास॑ ॥

Then there was neither death nor immortality Nor was there then the torch of night and day. The One breathed windlessly and self-sustaining. There was that One then, and there was no other.

RV 10.129.3

तम॑ आसी॒त्तम॑सा गू॒ळ्हमग्रे॑ऽप्रके॒तं स॑लि॒लं सर्व॑मा इ॒दं ।
तु॒च्छ्येना॒भ्वपि॑हितं॒ यदासी॒त्तप॑स॒स्तन्म॑हि॒नाजा॑य॒तैकं॑

At first there was only darkness wrapped in darkness.
All this was only unillumined water.
That One which came to be, enclosed in nothing,
arose at last, born of the power of heat.

RV 10.129.4
काम॒स्तदग्रे॒ सम॑वर्त॒ताधि॒ मन॑सो॒ रेत॑: प्रथ॒मं यदासी॑त् ।
स॒तो बन्धु॒मस॑ति॒ निर॑विन्दन्हृ॒दि प्र॒तीष्या॑ क॒वयो॑ मनी॒षा ॥

In the beginning there was desire,
which was the first seed of mind
sages having meditated in their
hearts have discovered by their wisdom
the connection of the existent with the non-existent

RV 10.129.5
ति॒र॒श्चीनो॒ वित॑तो र॒श्मिरे॑षाम॒धः स्वि॑दा॒सी३दु॒परि॑ स्विदासी३त् ।
रे॒तो॒धा आ॑सन्महि॒मान॑ आसन्त्स्व॒धा अ॒वस्ता॒त्प्रय॑तिः प॒रस्ता॑त् ॥

And they have stretched their cord across the void,
and know what was above, and what below.
Seminal powers made fertile mighty forces.
Below was strength, and over it was impulse

RV 10.129.6
को अ॒द्धा वे॑द॒ क इ॒ह प्र वो॑च॒त्कुत॒ आजा॑ता॒ कुत॑ इ॒यं विसृ॑ष्टिः ।
अ॒र्वाग्दे॒वा अ॒स्य वि॒सर्ज॑ने॒नाथा॒ को वे॑द॒ यत॑ आब॒भूव॑ ॥

But, after all, who knows, and who can say
Whence it all came, and how creation happened?
The gods themselves are later than creation,
so who knows truly whence it has arisen?
 

RV 10.129.7
इ॒यं विसृ॑ष्टि॒र्यत॑ आब॒भूव॒ यदि॑ वा द॒धे यदि॑ वा॒ न ।
यो अ॒स्याध्य॑क्षः पर॒मे व्यो॑म॒न्त्सो अ॒ङ्ग वे॑द॒ यदि॑ वा॒ न वेद॑ ॥

Whence all creation had its origin,
he, whether he fashioned it or whether he did not,
he, who surveys it all from highest heaven,
he knows - or maybe even he does not know. 

What are the Indo European languages?

The Indo-European languages are a family of languages spoken in Europe, Iran and the northern part of South Asia including Afghanistan, Pakistan and North India. 

Linguists have classified the Indo-European languages into 10 families  - Albanian, Armenian, Indo-Iranian, Greek, Italic, Germanic, Celtic, Balto-Slavic, Anatolian and Tocharian. 

There are several papers in peer reviewed journals that show the grammatical similarity between Sanskrit and other Indo European languages.  The interested reader can start with the Wikipedia page on Indo European languages and follow the references from there.

By contrast, Dravidian languages are linguistically isolated from other language families. The Dravidian languages include Kannada, Tamil, Telugu and Malayalam spoken in South India and some parts of northern Sri Lanka, Brahui spoken in Baluchistan and Gondi spoken in Central India. Inscriptions in Tamil-Brahmi script have been dated from the 2nd century to the 6th century BCE in Keeladi in Tamil Nadu. 

Who are the Andamanese Hunter Gatherers? 

In the paper by Narasimhan et al in Science the authors state that the Andamanese Hunter Gatherers (AHG) are represented by present day tribes in the Andaman Islands. They hypothesize that they are related to indigenous unsampled South Asians. They are also referred to as Ancient Ancestral South Indians (AASI)

In the paper by Shinde et al in Cell, the AHG represent the hunter-gatherer population of South Asia. They write that present day South Asians have "ancestry deeply related to Andamanese hunter-gatherers"

The present day population of Indians derive their ancestry from Ancient South Indians (ASI) who have a mixture of AASI and hunter gatherers from Iran and Ancient North Indians who have a mixture of AASI, hunter gatherers from Iran and pastoralists from the Steppe region.  See Fig.36 in the chapter titled Mehrgarh. 

Why do experts in the field believe that the AHG represent Ancestral South Indians? 

In the chapter on Paleogenetics, we discussed the Out of Africa migration about 65,000 to 70,000 years ago.  Homo Sapiens crossed the Bab El-Mandeb strait to the Arabian peninsula and made their way to the Indian sub continent on their way to South East Asia and traveled as far as Australia. Some of these migrants made their way to the Andaman and Nicobar Islands in the Bay of Bengal, more than 1000 kms from the Indian mainland. 
How could this migration across 1000 kms of the ocean have happened? It is believed that this happened at the end of the Last Glacial Period about 20,000 to 25,000 years ago when sea levels were much lower,  reducing the distance to be traveled over water. 

There are several tribes in the Islands. These include the Great Andamanese, the Jarawa, the Onge and the Sentinelese. The Jarawa and the Sentinelese maintain a forest dwelling lifestyle. The Great Andamanese and the Onge receive aid from the Indian Government.

In a study titled, Genetic Affinities of the Andaman Islanders, a Vanishing Human Population, published in 2003, the authors analyzed the mtDNA and Y haplogroups from  blood samples from 68 Onge, 20 Great Andamanese, and 14 Nicobarese and 47 hair sampled collected at the beginning of the 20th century.  

The Onge and Jarawa had the Y-haplogroup D seen in Asia. The Nicobarese had Y-haplogroup  O seen in Southeast Asia. The Great Andamanese had O, L, K and P haplogroups.  This is due to their forced coexistence by the British with labourers and convicts from mainland India. 

All the Onge, Jarawa and all but two of the Great Andamanese had the M mtDNA haplogroup. The Nicobarese had mtDNA haplogroup B and F. The authors conclude that the Andamanese have more affinity with Asians than with Africans. They have low genetic variability because of their small population and reproductive isolation. The Nicobarese have genetic affinities to populations distributed throughout Asia. The authors state that the Nicobarese  "resemble  the Burmese in physical appearance and speak languages of the Austroasiatic family of mainland Southeast Asia" and have genetic affinity with Southeast Asians.

In a paper titled, Reconstructing the Origins of Andaman Islanders published in 2005, the authors analyzed the complete mtDNA sequence of five Onge, five Great Andamanese, and five Nicobarese individuals. It was known from a previous study that they had M2 and M4 mtDNA haplogroups. The Onge and Great Andamanese showed two new haplogroups, M31 and M32.  The authors believe these two haplogroups developed in situ on the islands.  The Nicobarese mtDNA haplogroup clade F1a1a1 has been seen in China, Malaysia and Thailand, pointing to their affinity with Southeast Asians. 

 The low genetic diversity, the presence of the mtDNA haplogroup M2 which is believed to be about 50kya old and is predominantly found among those speaking Dravidian languages and tribal populations of India and the Y haplogroup D that is about 70kya old  have suggested to geneticists that the AHG can be used as a proxy for AASI. 

In an interview, Narasimhan had this to say - "There is the misconception that, when we describe ancestral sources, it implies one population moved to another part of the world. Here we use “related” to refer to the fact that two populations descend from a common ancestor. In this case, the ancestry in modern Indians is very deeply related to the Andamanese hunter-gatherers. By deeply, I mean this ancestry type diverged about 30,000 years ago from the Andamanese hunter-gatherers today. We use the Andamanese hunter-gatherers as a proxy because we don’t have any source populations for that ancestry type which are not mixed with any other group. Thus, the Andamanese hunter-gatherers are used as a proxy population to reflect what the ancestry of the first hunter-gatherers of India used to look like. So, this particular ancestry refers to the first group of people who peopled the southeast of India at some point of time. We don’t know when exactly, but it is a substrate that permeates through most of India. "

How can the analysis of DNA from a few dozen or hundred samples be sufficient to arrive at important conclusions on the origins of Indians or the peopling of the world?

The paper in Cell was based on the study of one skeleton found in Rakhigarhi and DNA from 11 samples from Gonur in Turkmenistan. The paper in Science was based on more than 800 samples. Still, this is not a large sample. How can this be sufficient?
The answer lies in the fact that the genome from a few individuals is representative of the population. For example, Steppe ancestry has been seen in some communities like Brahmins and Bhumihars. If we look at the DNA of hundreds or thousands of Brahmins, we would see the same Steppe ancestry signature, perhaps in different proportions but that does not detract from the argument. Similarly, the DNA of people from the Irula or Panniyar tribes in South India have little or no  Steppe ancestry. It is not necessary to look at the DNA of everyone in that community. In addition, the endogamous nature of Indian society, where people married only within their caste or community, has reduced genetic diversity, removing the need to sample everyone.

As an aside, endogamy makes it difficult to trace ancestry across populations which depends on identifying shared variants across different groups

In the same interview, Narasimhan had this to say - "People are too concerned about it being a single sample and I want to talk about this directly. There are again misconceptions here. The first [thing to know] is that a single genome not just integrates information across thousands of that person’s ancestors, it is actually extremely informative about the genetics of the population. It is not necessary to sample hundreds of individuals, you actually end up just getting repeat information in many cases. "

"Taken together, these 11 samples and the single individual from Rakhigarhi are the source population for 110 samples that we have access to from the Swat Valley in Pakistan and thousands and thousands of samples that we have access to from modern-day India. In fact, we show that they are the only possible source population from over five hundred samples that we have from Central Asia and Iran which are geographically proximate to India. That these others are not the source populations and only these samples are the source populations is telling you that this must be reflecting a type of ancestry that must have been present across northwestern India in the Bronze Age. Therefore, these 11 samples along with the single individual from Rakhigarhi confine the ancestry in a way. Even with additional sampling it is likely that we are only going to be sampling from this genomic distribution "