Roopkund lake amidst the Himalayan mountains has been a place of mystery. It is a shallow lake which is filled with the bones of human beings, due to which it is also known as Skeleton Lake and the reason behind the presence of skeletons is not yet known.
One hypothesis is that a large number of people died due to a single catastrophe. However, this idea is now challenged by DNA analysis of 38 skeletons present there. It reveals that different groups of people from distant places such as the Mediterranean came to the lake over a period of 1000 years. The paper appears in the journal Nature Communications.
David Reich, a geneticist from Harvard Medical School said that biomolecular analysis including radiocarbon dating and stable isotope dietary reconstruction reveals the history of the lake to be more complex than imagined. Geneticist Kumarasamy Thangaraj, CSIR Centre for Cellular and Molecular Biology sequenced mitochondrial DNA of 72 skeletons a decade ago. Some skeletons had DNA of a local Indian origin however several appeared to have come from West Eurasia. This led to a deeper analysis of genome sequencing in which genome-wide DNA was produced for 38 persons. These were compared against 1521 ancient and 7985 current persons from all over the world. 23 persons had similar DNA to that of people from India however 14 persons had similar DNA to that of residents in current Greece and Crete. And one person had DNA from Southeast Asian origin.
Eadaoin Harney, Harvard University said that scientists are highly surprised by this variation in the genetics of the skeletons. That the DNAs of the skeletons reveal similarities with the eastern Mediterranean suggests that the Lake attracted visitors from all over the world. Isotope analysis supports these findings. Some stable isotopes can be absorbed in plants which are then eaten by people. These replace some calcium in bones and teeth which can be matched suitably to specific locations.
Ayushi Nayak, archaeologist of Max Planck Institute for Science of Human History said that persons with Indian origins had a diet mainly depending on C3 and C4 derived food sources. It is consistent with the genetic evidence that they belonged to several socioeconomic groups in South Asia. However, people connected to the eastern Mediterranean had a diet with a lesser amount of millet.
What is even more mind-boggling is the time of arrival of these groups. Radiocarbon dating estimates that the bones related to Indian ancestry came between the 7th and 10th centuries and those from the Mediterranean and Southeast Asia were dated between the 17th and 20th centuries. It is very much possible that skeletons not tested could belong to other regions from different time periods.
We still do not know how these persons came to the Lake and what is the cause of their death. Scientists have to dig deeper to find the answers.
Journal Reference: Nature Communications