WASHINGTON, Sept 6, 2019 (BSS/AFP) – For decades, researchers have debated
how Indo-European languages came to be spoken from the British Isles to South
Asia.
Now, the largest-ever study of ancient human DNA suggests that the answer
may lie with a mass migration of Bronze Age herders from the Eurasian
Steppes, starting 5,000 years ago, westward to Europe and east to Asia.
Vagheesh Narasimhan, co-first author of the paper published in the journal
Science on Thursday, told AFP that the role of population movements over the
past 10,000 years was key to understanding linguistic changes and the
transition from hunter-gatherer activities to farming.
“There’s been a lot of DNA work, as well as archeological work, about both
of these processes in Europe,” the postdoctoral fellow at Harvard Medical
School explained, but these transformations are less understood in Asia.
A global team of geneticists, archeologists and anthropologists analyzed
the genomes of 524 never-before-studied ancient individuals from Central and
South Asia, increasing the worldwide total of published ancient genomes by
about 25 percent.
By comparing the genomes to one another and to previously discovered
remains, and by placing that information into its historical context through
archeological and linguistic records, the team was able to fill the gaps in
our current understanding.
A 2015 paper indicated that Indo-European languages — the world’s biggest
language group that includes Hindi-Urdu, Farsi, Russian, English, French,
Gaelic and more than 400 others — arrived in Europe via the steppes.
Despite being spread over a vast area encompassing myriad cultures, these
languages share uncanny similarities in syntax, numbers, basic adjectives and
numerous nouns including those related to kin, body parts and more.
The path of the proto-Indo European languages to Asia was less clear: one
school of thought held they spread from farmers from Anatolia (present-day
Turkey).
But the paper found that present-day South Asians have little if any shared
ancestry with these ancient Anatolian farmers.
“We can rule out a large-scale spread of farmers with Anatolian roots into
South Asia, the centerpiece of the ‘Anatolian hypothesis’ that such movement
brought farming and Indo-European languages into the region,” said co-author
David Reich, also at Harvard Medical School.
“Since no substantial movements of people occurred, this is checkmate for
the Anatolian hypothesis.”
– Indus Valley Civilization –
There are two new lines of evidence in favor of steppe origin. First, the
researchers detected genetic similarities that connect speakers of the Indo-
Iranian and Balto-Slavic branches of Indo-European.
They found that the present-day speakers of both these groups descend from
a subgroup of steppe herders who moved west toward Europe 5,000 years ago,
then spread back east to Central and South Asia in the following 1,500 years.
Another observation in favor of the theory: South Asians who today speak
Dravidian languages (mainly in southern India and southwestern Pakistan) had
very little steppe DNA, while those who speak Indo-European languages like
Hindi, Punjabi, Bengali have far more.
As far as agriculture is concerned, prior work has found that farming
spread to Europe via people of Anatolian ancestry.
South Asians, however, share little to no ancestry with the Anatolians,
ruling them out, while the archeological record shows the activity also
predates the steppe herders, leading researchers to conclude agriculture
arrived independently in the region.
A second paper, meanwhile, published in the journal Cell Press by several
of the same authors, describes the first genome of an individual from the
Indus Valley Civilization (IVC), one of the great civilizations of the
ancient world contemporaneous with Egypt and Mesopotamia.
Its towns, which first appeared 3000 years BCE, were populated by tens of
thousands of people, who used standardized weights and measures, built great
roads and traded with places as far away as East Africa.
The team was able to overcome technical challenges posed by the hot, humid
and monsoonal climate to sequence for the first time a Bronze Age individual
from South Asia.
The DNA belongs to a woman who lived four to five millennia ago buried at
Rakhigarhi, the biggest town of the IVC, also known as the Harappan
civilization.
Based on their findings, the authors believe that modern South Asians are
descended from the Harappan people who later mixed with steppe herders who
migrated from the north.
Beyond its academic value, sequencing ancient DNA can help improve modern
genome studies that look at genetic predisposition for diseases, a burgeoning
area of medicine.
“In Europe, this has been widely studied, and people use these all the time
in medical studies, but in South and Central Asia, there’s been a paucity of
this — and this paper sort of helps close that gap,” Narasimhan told AFP.