Mysterious skeletons of Skeleton lake belong to genetically highly distinct groups

The lake was thought to be the site of an ancient catastrophic event that left several hundred people dead, but the first ancient whole-genome data from India shows that diverse groups of people died at the lake in multiple events approximately 1000 years apart.

Situated at over 5,000 meters above sea level in the Himalayan Mountains, Roopkund Lake is home to the dissipated skeletal remains of several hundred people of unknown origin. The lake has long puzzled scientists thinking about who these individuals were, what brought them to Roopkund Lake, and how they died.

There have been multiple proposals to explain the origins of these skeletons. It has also been suggested that these are the remains of an army or group of merchants who were caught in a storm. Finally, it has been suggested that they were the victims of an epidemic.

Now a study conducted by the international team of scientists has revealed that the mysterious skeletons belong to genetically highly distinct groups that died in multiple periods in at least two episodes separated by one thousand years.

Researchers analyzed the remains using a series of bioarcheological analyses, including ancient DNA, stable isotope dietary reconstruction, radiocarbon dating, and osteological examination. They found that Roopkund skeletons belong to three genetically distinct groups that were deposited during multiple events, isolated in time by around 1000 years. These discoveries disprove past proposals that the skeletons of Roopkund Lake were deposited in a single catastrophic event.

Ayushi Nayak preparing samples for analysis in the Stable Isotope Laboratory at the Max Planck Institute for the Science of Human History. The Photo is a screen grab from the video "Sampling and Pretreatment of Tooth Enamel Carbonate for Stable Carbon and Oxygen Isotope Analysis" which can be found at: www.shh.mpg.de/1032332 © Ventresca Miller, A., Fernandes, R., Janzen, A., Nayak, A., Swift, J., Zech, J., Boivin, N., Roberts, P. Sampling and Pretreatment of Tooth Enamel Carbonate for Stable Carbon and Oxygen Isotope Analysis. J. Vis. Exp. (138), e58002, doi:10.3791/58002 (2018).
Ayushi Nayak preparing samples for analysis in the Stable Isotope Laboratory at the Max Planck Institute for the Science of Human History. The Photo is a screen grab from the video “Sampling and Pretreatment of Tooth Enamel Carbonate for Stable Carbon and Oxygen Isotope Analysis” which can be found at: www.shh.mpg.de/1032332
© Ventresca Miller, A., Fernandes, R., Janzen, A., Nayak, A., Swift, J., Zech, J., Boivin, N., Roberts, P. Sampling and Pretreatment of Tooth Enamel Carbonate for Stable Carbon and Oxygen Isotope Analysis. J. Vis. Exp. (138), e58002, doi:10.3791/58002 (2018).

Co-senior author Kumarasamy Thangaraj of CCMB, who started the project more than a decade ago said, “We first became aware of the presence of multiple distinct groups at Roopkund after sequencing the mitochondrial DNA of 72 skeletons. While many of the individuals possessed mitochondrial haplogroups typical of present-day Indian populations, we also identified a large number of individuals with haplogroups that would be more typical of populations from West Eurasia.”

The leading group is made out of 23 individuals with ancentries that are related with individuals from present-day India, who don’t seem to belong to a single population, however, instead got from a wide range of groups. Surprisingly, the second biggest group is comprised of 14 people with ancestry that is most closely related to individuals who live in the eastern Mediterranean, mainly present-day Crete and Greece. A third individual has ancestry that is more typical of that found in Southeast Asia.

First-author Éadaoin Harney of Harvard University said, “We were extremely surprised by the genetics of the Roopkund skeletons. The presence of individuals with ancestries typically associated with the eastern Mediterranean suggests that Roopkund Lake was not just a site of local interest, but instead drew visitors from across the globe.”

Co-senior author Ayushi Nayak of the Max Planck Institute for the Science of Human History said, “Stable isotope dietary reconstruction of the skeletons also supports the presence of multiple distinct groups. “Individuals belonging to the Indian-related group had highly variable diets, showing reliance on C­3 and C4 derived food sources. These findings are consistent with the genetic evidence that they belonged to a variety of socioeconomic groups in South Asia.”

“In contrast, the individuals with eastern Mediterranean-related ancestry appear to have consumed a diet with very little millet.”

Radiocarbon dating indicates that the skeletons were not deposited at the same time, as previously assumed. Instead, the study finds that the two major genetic groups were deposited approximately 1000 years apart.

First, during the 7th-10th centuries CE, individuals with Indian-related ancestry died at Roopkund, possibly during several distinct events. It was not until sometime during the 17th-20th centuries that the other two groups, likely composed of travelers from the eastern Mediterranean and Southeast Asia arrived at Roopkund Lake.

Co-senior author Douglas J. Kennett of the University of California, Santa Barbara said, “This finding shows the power of radiocarbon dating, as it had previously been assumed that the skeletons of Roopkund Lake were the result of a single catastrophic event.”

Senior author Niraj Rai, of the Birbal Sahni Institute of Palaeosciences in Lucknow, India said, “It is still not clear what brought these individuals to Roopkund Lake or how they died. We hope that this study represents the first of many analyses of this mysterious site.”

Co-senior author David Reich of Harvard Medical School said, “Through the use of biomolecular analyses, such as ancient DNA, stable isotope dietary reconstruction, and radiocarbon dating, we discovered that the history of Roopkund Lake is more complex than we ever anticipated, and raises the striking question of how migrants from the eastern Mediterranean, who have an ancestry profile that is extremely atypical of the region today, died in this place only a few hundred years ago. This study highlights the power of biomolecular tools to provide unexpected insights into our past.”

The study, published this week in Nature Communications.

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