Every summer, hundreds of ancient bones
emerge from the ice. A new genetic study helps explain how they got there.
By
Robin George Andrews
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Roopkund
Lake, in the Indian Himalayas, is frozen for much of the year. But in
warmer
months it delivers a macabre performance, earning the nickname
Skeleton
Lake.Credit Atish Waghwase
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Nestled in the Indian Himalayas, some 16,500
feet above sea level, sits Roopkund Lake. One hundred and thirty feet wide, it
is frozen for much of the year, a frosty pond in a lonely, snowbound valley.
But on warmer days, it delivers a macabre performance, as hundreds of human
skeletons, some with flesh still attached, emerge from what has become known as
Skeleton Lake.
Who were these individuals, and what befell
them? One leading idea was that they died simultaneously in a catastrophic
event more than 1,000 years ago. An unpublished anthropological survey from
several years ago studied five skeletons and estimated they were 1,200 years
old.
But a new genetic analysis carried out by
scientists in India, America and Germany has upended that theory. The study,
which examined DNA from 38 remains, indicates that there wasn’t just one mass
dumping of the dead, but several, spread over a millennium.
The report, published Tuesday in Nature
Communications, has led to a “far richer view into the possible histories of
this site” than previous efforts provided, said Jennifer Raff, a geneticist and
anthropologist at the University of Kansas who was not involved with the work.
Anthropologists have known about Roopkund
Lake for several decades, but little was known about the provenance of its
skeletons. Rockslides, migrating ice and even human visitors have disturbed and
moved the remains, making it difficult to decipher when and how the individuals
were buried, much less who they were. “In a case like this, that becomes
impossible,” said Cat Jarman, a bioarchaeologist at the University of Bristol
in England who was not part of the research team.
Genetic analysis has helped make some sense
of the jumble of bones. The researchers, led in part by Niraj Rai, an expert in
ancient DNA at the Birbal Sahni Institute of Palaeosciences in India, and David
Reich, a geneticist at Harvard University, extracted DNA from the remains of
dozens of skeletal samples, and managed to identify 23 males and 15 females.
Based on populations living today, these
individuals fit into three distinct genetic groups. Twenty-three, including
males and females, had ancestries typical of contemporary South Asians; their
remains were deposited at the lake between the 7th and 10th centuries, and not
all at once. Some skeletons were more ancient than others, suggesting that many
were interred at the lake lifetimes apart.
Then, perhaps 1,000 years or so later,
sometime between the 17th and 20th centuries, two more genetic groups suddenly
appeared within the lake: one individual of East Asian-related ancestry and,
curiously, 14 people of eastern Mediterranean ancestry.
How all these individuals met their end is
anyone’s guess. There’s no evidence of bacterial infections, so an epidemic was
probably not to blame. Perhaps the challenging high-altitude environment proved
fatal.
The earlier study, of five skeletal samples,
found three with unhealed compression fractures, perhaps inflicted by huge
hailstones, although that conclusion is open to debate. In any case, across a
range of centuries “it’s hard to believe that each individual died in exactly
the same way,” said Éadaoin Harney, a doctoral student at Harvard and the lead
author on the study.
The individuals included children and elderly
adults, but none were family relatives. Chemical signatures from the skeletons
indicate that the individuals had significantly different diets, adding support
to the notion that several distinct population groups are represented.
If accounts of their journeys exist
somewhere, none have been uncovered so far. “We have searched all the archives,
but no such records were found,” said Dr. Rai.
The researchers note that Roopkund Lake is
situated on a route known to modern-day Hindu pilgrims, so perhaps some of the
South Asian individuals died while taking part. But that is less likely to
explain the presence of individuals from the distant eastern Mediterranean.
Perhaps they weren’t actually Mediterranean
migrants, Dr. Jarman said. Their genetic ancestry resembles that of present-day
people from Greece or Crete, but current distribution may not apply to ancient
populations. Regardless, this group came from somewhere far from Roopkund Lake,
for reasons unknown.
Maybe the site held significance for groups
with various religious beliefs, said Dr. Jarman. Maybe some of the skeletons
were brought for burial, possibly to be left in the lake. Or maybe there were
ill-fated explorers — driven by a desire to see a spectacular mountain range,
killed by their own curiosity.
A few answers have begun to emerge, at least.
Archaeology is full of such enigmatic sites, Dr. Reich said, and when science
comes along and digs in, “it enriches the story in immeasurable ways.”
@ The New York Times
