[The study, presented here last week at the meeting of the American Association of Physical Anthropologists and in a preprint on the bioRxiv server, sheds light on where these populations came from and when they arrived in South Asia. It also strengthens the claim that Proto-Indo-European (PIE)—the ancestral language that gave rise to modern languages from English to Russian to Hindi—originated on the steppes of Asia.]
By Lizzie
Wade
 |
|
Three
ancestral groups gave rise to the diverse people of South Asia today. Mary
Doggett/Alamy Stock Photo
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AUSTIN — Today,
the population of South Asia is divided into dozens of ethnic, linguistic, and
religious groups that live side by side—but not always in harmony. A
contentious border separates India and Pakistan; political movements draw stark
lines between India’s Muslim and Hindu populations. Groups don’t mix much, as
people tend to marry those who share their ethnicity and tongue.
Now,
a study of the first ancient DNA recovered from South Asia shows that
populations there mingled repeatedly thousands of years ago. Nearly all of the
Indian subcontinent’s ethnic and linguistic groups are the product of three
ancient Eurasian populations who met and mixed: local hunter-gatherers, Middle
Eastern farmers, and Central Asian herders. Three similar groups also mingled
in ancient Europe, giving the two subcontinents surprisingly parallel
histories.
The
study, presented here last week at the meeting of the American Association of
Physical Anthropologists and in a preprint on the bioRxiv server, sheds light
on where these populations came from and when they arrived in South Asia. It
also strengthens the claim that Proto-Indo-European (PIE)—the ancestral
language that gave rise to modern languages from English to Russian to Hindi—originated
on the steppes of Asia.
“It’s
first-rate work,” says Partha Majumder, a geneticist at the National Institute
of Biomedical Genomics in Kalyani, India. He found hints of similar genetic
patterns in his previous studies, but the addition of ancient DNA makes the new
conclusions stronger, he says. “It’s absolutely stunning.”
Priya
Moorjani, a geneticist at the University of California, Berkeley, studies how
South Asian populations relate to each other and to others around the world. In
previous work, she analyzed the genomes of nearly 600 modern Indians and
Pakistanis from 73 ethnolinguistic groups in South Asia. Her team found that
almost all people living in India today carry ancestry from two ancient
populations: Ancestral North Indians, who were more related to people from
Central Asia, the Middle East, the Caucasus, and Europe; and Ancestral South
Indians, who were more related to indigenous groups living in the subcontinent
today. But without DNA from ancient people, Moorjani couldn’t be sure who gave
rise to those ancestral populations, or when.
Moorjani,
David Reich of Harvard University, and Kumarasamy Thangaraj of the Centre for
Cellular and Molecular Biology in Hyderabad, India, spent years searching for
ancient DNA in South Asia, where hot climates might degrade it. Finally, their
team recovered and analyzed ancient genomes from 65 individuals who lived in
northern Pakistan between 1200 B.C.E. and 1 C.E. They also analyzed 132 ancient
genomes from Iran and southern Central Asia, and 165 from the steppes of
Kazakhstan and Russia, and compared them with published ancient and modern
genomes. These data allowed them to reconstruct when different populations
arrived in South Asia and how they interacted.
Between
4700 and 3000 B.C.E., farmers from Iran mixed with hunter-gatherers indigenous
to South Asia, Moorjani said. This combination of ancestries was found in the
DNA of skeletal remains from sites in Turkmenistan and Iran known to have been
in contact with the Indus Valley civilization, which thrived in Pakistan and
northwest India starting around 3300 B.C.E. The researchers dub this population
“Indus periphery.” The 65 ancient people from Pakistan also show this
combination, although they all lived after the Indus civilization declined. The
researchers suspect that “Indus periphery” people actually may have been the
founders of Indus society, although without ancient DNA from Indus Valley
burials, they can’t be sure.
Still,
Moorjani’s team sees this ancient mixture of Iranian farmers and South Asian
hunter-gatherers all over South Asia today. As the Indus Valley civilization
declined after 1300 B.C.E., some Indus periphery individuals moved south to mix
with indigenous populations there, forming the Ancestral South Indian
population, which today is more prominent in people who speak Dravidian
languages such as Tamil and Kannada, and in those belonging to lower castes.
Meanwhile,
herders from the Eurasian steppe moved into the northern part of the
subcontinent and mixed with Indus periphery people still there, forming the
Ancestral North Indian population. Today, people who belong to higher castes
and those who speak Indo-European languages such as Hindi and Urdu tend to have
more of this ancestry. Shortly after, these two already mixed groups mixed with
each other, giving rise to the populations living in India today.
“Strikingly,
this is very similar to the pattern we see in Europe,” Moorjani said. Around
7000 B.C.E., agriculture spread into both Europe and South Asia with farmers
from Anatolia and Iran, respectively, who each mixed with local hunter-gatherer
populations. After about 3000 B.C.E., Yamnaya pastoralists from the Central
Asian steppe swept both east and west, into Europe and South Asia, bringing the
wheel and perhaps cannabis.
Earlier
genetic work had linked the arrival of these herders to the spread of
Indo-European languages in Europe. But other researchers, including
archaeologist Colin Renfrew of the University of Cambridge in the United
Kingdom, had argued that the earlier Anatolian farmers were the original PIE
speakers. The new data “make a strong case” for the Yamnaya as carriers of Indo-European
languages, Renfrew says. But he still thinks Anatolian farmers could have
spoken the earliest language in that family.
@
Science
