The study
Titled ‘The Genomic Formation of South and Central Asia’, the study looks
at “ancient DNA” from 357 individuals from Central and South Asia
to say that there was indeed some kind
of migration into India around the 2nd millennium BCE, towards the end of the
Indus Valley Civilisation. Overall, the dataset included 612 ancient
individuals that were then co-analysed with genome-wide data from present-day
individuals. The study which is yet to be peer-reviewed does not use the term ‘Aryan’. It says Steppe pastoralists around the Volga and Don rivers in Russia moved
towards India encountering the Indus Valley population. “[T]hey mixed with
a more southern population that we document at multiple sites as outlier
individuals exhibiting a distinctive mixture of ancestry related to Iranian
agriculturalists and South Asian hunter-gatherers,” the study states.
Mixing of population groups
The study is based on the
understanding that present-day South
Asians have descended from a mixture of two highly divergent populations:
Ancestral North Indians (ANI) and Ancestral South Indians (ASI). The
research reveals a complex set of genetic sources that combine three potential
groupings that mixed together in various ways to create the ANI and ASI. The
first are the South Asian hunter-gatherers, who are described in the study as
AASI or Ancient Ancestral South Indians.
These were the Onge or the
indigenous population of the Andaman Islands. Second, is the Iranian agriculturalists, represented
by 8th millennium BCE pastoralists from the Zagros mountains, who were known to have come to the subcontinent.
Then, there are the Steppe pastoralists, often loosely referred to as the ‘Aryans’,
who inhabited the vast Central Asia grasslands. The study reveals that in the beginning, the Indus Valley
population was a result of the mixing of first and second groups. Then the Steppe pastoralists moved
Southwards and mixed with the Indus Valley population. Further, people from Indus Valley moved southwards to merge with the
South Asian hunter-gatherers to form the ASI. In the meantime, a genome admixture took place in the north
between the population from the Steppe and the Indus Valley to create the ANI
population stock. Later, the ANI and ASI continued to mix with each other
to create almost the entire ancestry of South Asian population. The study works
with the Indus Valley Periphery data and uses data of individuals from Central
Asian sites that they believe to be related to the Indus Valley people, even as
genetic data from the Harappan sites are yet to be released.
Another finding is the connection between the Steppe pastoralists
and the priestly castes, and cultures of North India. The research finds
that 10 out of 140 Indian groups studied
have a higher amount of Steppe ancestry than Indus Valley ancestry, the highest two were ‘Brahmin-Tiwari’ and
‘Brahmin-UP’. The study points out that “although the enrichment for Steppe ancestry is not found in southern Indian groups,
the Steppe enrichment in the northern groups is striking as Brahmins and
Bhumihars are among the traditional custodians of texts written in early
Sanskrit”.
Significance
According to author and former
Businessworld editor Tony Joseph, who has written extensively on early Indians,
the study is “pathbreaking” because DNA from 612 ancient individuals were
co-analysed with DNA from present-day individuals and “this is what makes this
study dramatically different from previous studies”. “In the last five years, the techniques for extracting and analysing
ancient DNA has improved by leaps and bounds, and this is helping us understand
our prehistory far better, not just in South Asia, but around the world.
For example, in the last five years, we have learnt that Europe went through
two major mass migrations that changed their demography, and in the same
period, we have also learnt that the Americas,
before European arrivals, were peopled by at least four migrations from Asia.
So the findings about South Asia are just one part of the revolution that
ancient DNA is bringing to prehistory across the world.”
Essentially, Joseph points out,
the study shows that there are no “pure”
people anywhere — except perhaps in some very isolated and remote places
such as some of the Andaman and Nicobar islands. “We are all mixed. Almost all parts of the world have seen
repeated mass migrations that have deeply impacted their demography and India
is no exception. The genetic studies should be liberating in a way because
it should make us aware that we are all interconnected.”
David Reich, a geneticist at
Harvard Medical School and one of the authors of the study, too, points this
out in his new book, Who We Are and How We Got Here. Writing in the context of
a previous study that he worked on, in which he classified present-day Indians
as the outcome of mixtures between ANI and ASI, he said, “The ANI are related
to Europeans, central Asians, Near Easterners, and people of the Caucasus, but
we made no claim about the location of their homeland or any migrations. The
ASI descend from a population not related to any present-day populations
outside India. We showed that the ANI and ASI had mixed dramatically in India.
The result is that everyone in mainland India today is a mix, albeit in different
proportions, of ancestry related to West Eurasians, and… more closely related
to diverse East Asian and South Asian populations. No group in India can claim
genetic purity.”
Criticism
However, the study has invited
criticism from some. ICHR member and
guest professor at IIT Gandhinagar, Michel Danino, said that the study is
“steeped in circularity”. “It accepts the Indo-European migrations into Europe
and into South Asia as a fact, then repeatedly fits the genetic evidence to
this ‘fact’. This is faulty methodology…,” he said. He pointed out that “No
ancient Harappan DNA has been analysed, which could have provided some secure
comparison for contemporary samples in Central Asia and elsewhere.”
Danino also says that the study assumes that South Asia was more or
less empty of population in the pre-Harappan era. “It sweeps aside the subcontinent’s Mesolithic and Neolithic populations
which undoubtedly have substantial contributions to the South Asian genome.
It considers such Mesolithic and Neolithic populations only in the context of
Central Asia and Europe! This is one example [among others] of a strong
Eurocentric bias in the study,” he says.
Credit: Indian Explain Explained
(http://indianexpress.com/article/explained/the-long-walk-did-the-aryans-migrate-into-india-new-genetics-study-adds-to-debate/)
No comments:
Post a Comment