Post by Dr. Jai MaharajGenetics Might Be Settling The Aryan Migration Debate,
But Not How Left-Liberals Believe
By Anil Kumar Suri
Swarajya, swarajyamag.com
Monday, June 19, 2017
How genetics is settling the Aryan migration debate
Tony Joseph
June 16, 2017 23:49 IST
Updated: June 17, 2017 13:16 IST
New DNA evidence is solving the most fought-over question in Indian
history. And you will be surprised at how sure-footed the answer is,
writes Tony Joseph
The thorniest, most fought-over question in Indian history is slowly
but surely getting answered: did Indo-European language speakers, who
called themselves Aryans, stream into India sometime around 2,000 BC –
1,500 BC when the Indus Valley civilisation came to an end, bringing
with them Sanskrit and a distinctive set of cultural practices?
Genetic research based on an avalanche of new DNA evidence is making
scientists around the world converge on an unambiguous answer: yes,
they did.
This may come as a surprise to many — and a shock to some — because
the dominant narrative in recent years has been that genetics research
had thoroughly disproved the Aryan migration theory. This
interpretation was always a bit of a stretch as anyone who read the
nuanced scientific papers in the original knew. But now it has broken
apart altogether under a flood of new data on Y-chromosomes (or
chromosomes that are transmitted through the male parental line, from
father to son).
Lines of descent
Until recently, only data on mtDNA (or matrilineal DNA, transmitted
only from mother to daughter) were available and that seemed to
suggest there was little external infusion into the Indian gene pool
over the last 12,500 years or so. New Y-DNA data has turned that
conclusion upside down, with strong evidence of external infusion of
genes into the Indian male lineage during the period in question.
The reason for the difference in mtDNA and Y-DNA data is obvious in
hindsight: there was strong sex bias in Bronze Age migrations. In
other words, those who migrated were predominantly male and,
therefore, those gene flows do not really show up in the mtDNA data.
On the other hand, they do show up in the Y-DNA data: specifically,
about 17.5% of Indian male lineage has been found to belong to
haplogroup R1a (haplogroups identify a single line of descent), which
is today spread across Central Asia, Europe and South Asia.
Pontic-Caspian Steppe is seen as the region from where R1a spread both
west and east, splitting into different sub-branches along the way.
The paper that put all of the recent discoveries together into a tight
and coherent history of migrations into India was published just three
months ago in a peer-reviewed journal called ‘BMC Evolutionary
Biology’. In that paper, titled “A Genetic Chronology for the Indian
Subcontinent Points to Heavily Sex-biased Dispersals”, 16 scientists
led by Prof. Martin P. Richards of the University of Huddersfield,
U.K., concluded: “Genetic influx from Central Asia in the Bronze Age
was strongly male-driven, consistent with the patriarchal, patrilocal
and patrilineal social structure attributed to the inferred
pastoralist early Indo-European society. This was part of a much wider
process of Indo-European expansion, with an ultimate source in the
Pontic-Caspian region, which carried closely related Y-chromosome
lineages… across a vast swathe of Eurasia between 5,000 and 3,500
years ago”.
In an email exchange, Prof. Richards said the prevalence of R1a in
India was “very powerful evidence for a substantial Bronze Age
migration from central Asia that most likely brought Indo-European
speakers to India.” The robust conclusions of Professor Richards and
his team rest on their own substantive research as well as a vast
trove of new data and findings that have become available in recent
years, through the work of genetic scientists around the world.
What’s happened very rapidly, dramatically, and powerfully in the last
few years has been the explosion of genome-wide studies of human
history based on modern and ancient DNA, and that’s been enabled by
the technology of genomics and the technology of ancient DNA....”
David Reich, Geneticist and professor, Harvard Medical School
Peter Underhill, scientist at the Department of Genetics at the
Stanford University School of Medicine, is one of those at the centre
of the action. Three years ago, a team of 32 scientists he led
published a massive study mapping the distribution and linkages of
R1a. It used a panel of 16,244 male subjects from 126 populations
across Eurasia. Dr. Underhill’s research found that R1a had two
sub-haplogroups, one found primarily in Europe and the other confined
to Central and South Asia. Ninety-six per cent of the R1a samples in
Europe belonged to sub-haplogroup Z282, while 98.4% of the Central and
South Asian R1a lineages belonged to sub-haplogroup Z93. The two
groups diverged from each other only about 5,800 years ago. Dr.
Underhill’s research showed that within the Z93 that is predominant in
India, there is a further splintering into multiple branches. The
paper found this “star-like branching” indicative of rapid growth and
dispersal. So if you want to know the approximate period when
Indo-European language speakers came and rapidly spread across India,
you need to discover the date when Z93 splintered into its own various
subgroups or lineages. We will come back to this later.
So in a nutshell: R1a is distributed all over Europe, Central Asia and
South Asia; its sub-group Z282 is distributed only in Europe while
another subgroup Z93 is distributed only in parts of Central Asia and
South Asia; and three major subgroups of Z93 are distributed only in
India, Pakistan, Afghanistan and the Himalayas. This clear picture of
the distribution of R1a has finally put paid to an earlier hypothesis
that this haplogroup perhaps originated in India and then spread
outwards. This hypothesis was based on the erroneous assumption that
R1a lineages in India had huge diversity compared to other regions,
which could be indicative of its origin here. As Prof. Richards puts
it, “the idea that R1a is very diverse in India, which was largely
based on fuzzy microsatellite data, has been laid to rest” thanks to
the arrival of large numbers of genomic Y-chromosome data.
Gene-dating the migration
Now that we know that there WAS indeed a significant inflow of genes
from Central Asia into India in the Bronze Age, can we get a better
fix on the timing, especially the splintering of Z93 into its own
sub-lineages? Yes, we can; the research paper that answers this
question was published just last year, in April 2016, titled:
“Punctuated bursts in human male demography inferred from 1,244
worldwide Y-chromosome sequences.” This paper, which looked at major
expansions of Y-DNA haplogroups within five continental populations,
was lead-authored by David Poznik of the Stanford University, with Dr.
Underhill as one of the 42 co-authors. The study found “the most
striking expansions within Z93 occurring approximately 4,000 to 4,500
years ago”. This is remarkable, because roughly 4,000 years ago is
when the Indus Valley civilization began falling apart. (There is no
evidence so far, archaeologically or otherwise, to suggest that one
caused the other; it is quite possible that the two events happened to
coincide.)
The avalanche of new data has been so overwhelming that many
scientists who were either sceptical or neutral about significant
Bronze Age migrations into India have changed their opinions. Dr.
Underhill himself is one of them. In a 2010 paper, for example, he had
written that there was evidence “against substantial patrilineal gene
flow from East Europe to Asia, including to India” in the last five or
six millennia. Today, Dr. Underhill says there is no comparison
between the kind of data available in 2010 and now. “Then, it was like
looking into a darkened room from the outside through a keyhole with a
little torch in hand; you could see some corners but not all, and not
the whole picture. With whole genome sequencing, we can now see nearly
the entire room, in clearer light.”
Dr. Underhill is not the only one whose older work has been used to
argue against Bronze Age migrations by Indo-European language speakers
into India. David Reich, geneticist and professor in the Department of
Genetics at the Harvard Medical School, is another one, even though he
was very cautious in his older papers. The best example is a study
lead-authored by Reich in 2009, titled “Reconstructing Indian
Population History” and published in Nature. This study used the
theoretical construct of “Ancestral North Indians” (ANI) and
“Ancestral South Indians” (ASI) to discover the genetic substructure
of the Indian population. The study proved that ANI are “genetically
close to Middle Easterners, Central Asians, and Europeans”, while the
ASI were unique to India. The study also proved that most groups in
India today can be approximated as a mixture of these two populations,
with the ANI ancestry higher in traditionally upper caste and
Indo-European speakers. By itself, the study didn’t disprove the
arrival of Indo-European language speakers; if anything, it suggested
the opposite, by pointing to the genetic linkage of ANI to Central
Asians.
However, this theoretical structure was stretched beyond reason and
was used to argue that these two groups came to India tens of
thousands of years ago, long before the migration of Indo-European
language speakers that is supposed to have happened only about 4,000
to 3,500 years ago. In fact, the study had included a strong caveat
that suggested the opposite: “We caution that ‘models’ in population
genetics should be treated with caution. While they provide an
important framework for testing historical hypothesis, they are
oversimplifications. For example, the true ancestral populations were
probably not homogenous as we assume in our model but instead were
likely to have been formed by clusters of related groups that mixed at
different times.” In other words, ANI is likely to have resulted from
multiple migrations, possibly including the migration of Indo-European
language speakers.
The spin and the facts
But how was this research covered in the media? “Aryan-Dravidian
divide a myth: Study,” screamed a newspaper headline on September 25,
2009. The article quoted Lalji Singh, a co-author of the study and a
former director of the Centre for Cellular and Molecular Biology
(CCMB), Hyderabad, as saying: “This paper rewrites history… there is
no north-south divide”. The report also carried statements such as:
“The initial settlement took place 65,000 years ago in the Andamans
and in ancient south India around the same time, which led to
population growth in this part. At a later stage, 40,000 years ago,
the ancient north Indians emerged which in turn led to rise in numbers
there. But at some point in time, the ancient north and the ancient
south mixed, giving birth to a different set of population. And that
is the population which exists now and there is a genetic relationship
between the population within India.” The study, however, makes no
such statements whatsoever — in fact, even the figures 65,000 and
40,000 do not figure it in it!
This stark contrast between what the study says and what the media
reports said did not go unnoticed. In his column for Discover
magazine, geneticist Razib Khan said this about the media coverage of
the study: “But in the quotes in the media the other authors (other
than Reich that is - ed) seem to be leading you to totally different
conclusions from this. Instead of leaning toward ANI being
proto-Indo-European, they deny that it is.”
Let’s leave that there, and ask what Reich says now, when so much new
data have become available? In an interview with Edge in February last
year, while talking about the thesis that Indo-European languages
originated in the Steppes and then spread to both Europe and South
Asia, he said: “The genetics is tending to support the Steppe
hypothesis because in the last year, we have identified a very strong
pattern that this ancient North Eurasian ancestry that you see in
Europe today, we now know when it arrived in Europe. It arrived 4500
years ago from the East from the Steppe...” About India, he said: “In
India, you can see, for example, that there is this profound
population mixture event that happens between 2000 to 4000 years ago.
It corresponds to the time of the composition of the Rigveda, the
oldest Hindu religious text, one of the oldest pieces of literature in
the world, which describes a mixed society...” In essence according to
Reich, in broadly the same time frame, we see Indo-European language
speakers spreading out both to Europe and to South Asia, causing major
population upheavals.
The dating of the “profound population mixture event” that Reich
refers to was arrived at in a paper that was published in the American
Journal of Human Genetics in 2013, and was lead authored by Priya
Moorjani of the Harvard Medical School, and co-authored, among others,
by Reich and Lalji Singh. This paper too has been pushed into serving
the case against migrations of Indo-European language speakers into
India, but the paper itself says no such thing, once again!
Here’s what it says in one place: “The dates we report have
significant implications for Indian history in the sense that they
document a period of demographic and cultural change in which mixture
between highly differentiated populations became pervasive before it
eventually became uncommon. The period of around 1,900–4,200 years
before present was a time of profound change in India, characterized
by the de-urbanization of the Indus civilization, increasing
population density in the central and downstream portions of the
Gangetic system, shifts in burial practices, and the likely first
appearance of Indo-European languages and Vedic religion in the
subcontinent.”
The study didn’t “prove” the migration of Indo-European language
speakers since its focus was different: finding the dates for the
population mixture. But it is clear that the authors think its
findings fit in well with the traditional reading of the dates for
this migration. In fact, the paper goes on to correlate the ending of
population mixing with the shifting attitudes towards mixing of the
races in ancient texts. It says: “The shift from widespread mixture to
strict endogamy that we document is mirrored in ancient Indian texts.”
So irrespective of the use to which Priya Moorjani et al’s 2013 study
is put, what is clear is that the authors themselves admit their study
is fully compatible with, and perhaps even strongly suggests, Bronze
Age migration of Indo-European language speakers. In an email to this
writer, Moorjani said as much. In answer to a question about the
conclusions of the recent paper of Prof. Richards et al that there
were strong, male-driven genetic inflows from Central Asia about 4,000
years ago, she said she found their results “to be broadly consistent
with our model”. She also said the authors of the new study had access
to ancient West Eurasian samples “that were not available when we
published in 2013”, and that these samples had provided them
additional information about the sources of ANI ancestry in South
Asia.
One by one, therefore, every single one of the genetic arguments that
were earlier put forward to make the case against Bronze Age
migrations of Indo-European language speakers have been disproved. To
recap:
1. The first argument was that there were no major gene flows from
outside to India in the last 12,500 years or so because mtDNA data
showed no signs of it. This argument was found faulty when it was
shown that Y-DNA did indeed show major gene flows from outside into
India within the last 4000 to 4,500 years or so, especially R1a which
now forms 17.5% of the Indian male lineage. The reason why mtDNA data
behaved differently was that Bronze Age migrations were severely
sex-biased.
2. The second argument put forward was that R1a lineages exhibited
much greater diversity in India than elsewhere and, therefore, it must
have originated in India and spread outward. This has been proved
false because a mammoth, global study of R1a haplogroup published last
year showed that R1a lineages in India mostly belong to just three
subclades of the R1a-Z93 and they are only about 4,000 to 4,500 years
old.
3. The third argument was that there were two ancient groups in India,
ANI and ASI, both of which settled here tens of thousands of years
earlier, much before the supposed migration of Indo-European languages
speakers to India. This argument was false to begin with because ANI —
as the original paper that put forward this theoretical construct
itself had warned — is a mixture of multiple migrations, including
probably the migration of Indo-European language speakers.
Connecting the dots
Two additional things should be kept in mind while looking at all this
evidence. The first is how multiple studies in different disciplines
have arrived at one specific period as an important marker in the
history of India: around 2000 B.C. According to the Priya Moorjani et
al study, this is when population mixing began on a large scale,
leaving few population groups anywhere in the subcontinent untouched.
The Onge in the Andaman and Nicobar Islands are the only ones we know
to have been completely unaffected by what must have been a tumultuous
period. And according to the David Poznik et al study of 2016 on the
Y-chromosome, 2000 B.C. is around the time when the dominant R1a
subclade in India, Z93, began splintering in a “most striking” manner,
suggesting “rapid growth and expansion”. Lastly, from long-established
archaeological studies, we also know that 2000 BC was around the time
when the Indus Valley civilization began to decline. For anyone
looking at all of these data objectively, it is difficult to avoid the
feeling that the missing pieces of India’s historical puzzle are
finally falling into place.
The second is that many studies mentioned in this piece are global in
scale, both in terms of the questions they address and in terms of the
sampling and research methodology. For example, the Poznik study that
arrived at 4,000-4,500 years ago as the dating for the splintering of
the R1a Z93 lineage, looked at major Y-DNA expansions not just in
India, but in four other continental populations. In the Americas, the
study proved the expansion of haplogrop Q1a-M3 around 15,000 years
ago, which fits in with the generally accepted time for the initial
colonisation of the continent. So the pieces that are falling in place
are not merely in India, but all across the globe. The more the global
migration picture gets filled in, the more difficult it will be to
overturn the consensus that is forming on how the world got populated.
Nobody explains what is happening now better than Reich: “What’s
happened very rapidly, dramatically, and powerfully in the last few
years has been the explosion of genome-wide studies of human history
based on modern and ancient DNA, and that’s been enabled by the
technology of genomics and the technology of ancient DNA. Basically,
it’s a gold rush right now; it’s a new technology and that technology
is being applied to everything we can apply it to, and there are many
low-hanging fruits, many gold nuggets strewn on the ground that are
being picked up very rapidly.”
So far, we have only looked at the migrations of Indo-European
language speakers because that has been the most debated and argued
about historical event. But one must not lose the bigger picture: R1a
lineages form only about 17.5 % of Indian male lineage, and an even
smaller percentage of the female lineage. The vast majority of Indians
owe their ancestry mostly to people from other migrations, starting
with the original Out of Africa migrations of around 55,000 to 65,000
years ago, or the farming-related migrations from West Asia that
probably occurred in multiple waves after 10,000 B.C., or the
migrations of Austro-Asiatic speakers such as the Munda from East Asia
the dating of which is yet to determined, and the migrations of
Tibeto-Burman speakers such as the Garo again from east Asia, the
dating of which is also yet to be determined.
What is abundantly clear is that we are a multi-source civilization,
not a single-source one, drawing its cultural impulses, its tradition
and practices from a variety of lineages and migration histories. The
Out of Africa immigrants, the pioneering, fearless explorers who
discovered this land originally and settled in it and whose lineages
still form the bedrock of our population; those who arrived later with
a package of farming techniques and built the Indus Valley
civilization whose cultural ideas and practices perhaps enrich much of
our traditions today; those who arrived from East Asia, probably
bringing with them the practice of rice cultivation and all that goes
with it; those who came later with a language called Sanskrit and its
associated beliefs and practices and reshaped our society in
fundamental ways; and those who came even later for trade or for
conquest and chose to stay, all have mingled and contributed to this
civilization we call Indian. We are all migrants.
Tony Joseph is a writer and former editor of BusinessWorld. Twitter:
@tjoseph0010
https://t.co/2kB45iXJsO
--
Steve Hayes
http://www.khanya.org.za/stevesig.htm
http://khanya.wordpress.com