The study involving 28 researchers from institutions in India, the US and Europe revealed that the skeletons belonged to three genetically distinct groups.
The study, published in popular science journal 'Nature Communications', covered 38 skeletons found in Roopkund Lake and once thought to have died during a single catastrophic event. However, researchers found that they died in multiple periods separated by at least 1,000 years.
Genome-wide ancient DNA reveals that 23 of the individuals had ancestry that falls within the range of variation of present-day South As. A further 14 had ancestry typical of the eastern Mediterranean while one individual was found with Southeast Asian-related ancestry.
According to Hyderabad-based Centre for Cellular and Molecular Biology (CCMB), which was part of the study, it was the first ancient DNA ever reported from India.
Nestled deep in the Himalayan mountains at 5,029 metres above sea level, Roopkund Lake is colloquially referred to as "Skeleton Lake" due to the remains of several hundred ancient humans scattered around its shores.
"Little was known about the origin of these skeletons, as they have never been subjected to systematic anthropological or archaeological scrutiny, in part due to the disturbed nature of the site, which is frequently affected by rockslides, and which is often visited by local pilgrims and hikers who have manipulated the skeletons and removed many of the artifacts," says the study.
"There have been multiple proposals to explain the origins of these skeletons. Local folklore describes a pilgrimage to the nearby shrine of the mountain goddess, Nanda Devi, undertaken by a king and queen and their many attendants, who "due to their inappropriate, celebratory behaviour" were struck down by the wrath of Nanda Devi. 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."
The researchers analyzed the remains using a series of bioarcheological analyses, including ancient DNA, stable isotope dietary reconstruction, radiocarbon dating, and osteological analysis.
They obtained genome-wide data from 38 individuals by extracting DNA from powder drilled from long bones, producing next-generation sequencing libraries, and enriching them for approximately 1.2 million single nucleotide polymorphisms (SNPs) from across the genome.
A total of 76 skeletal samples (72 long bones and four teeth) were sampled at the Anthropological Survey of India, Kolkata. Skeletal sampling was performed in dedicated ancient DNA facilities at CCMB in Hyderabad.
A subset of samples were further processed at Harvard Medical School, Boston.
"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 genetic information typical of present-day Indian populations, we also identified a large number of individuals with genetic makeup that would be more typical of populations from West Eurasia (a term used in the study to refer to the cluster of ancestry types common in Europe, the Near East, and Iran)" says Kumarasamy Thangaraj, co-senior author and chief scientist at CCMB.
Dr Kumarasamy and then CCMB director Dr Lalji Singh, who is no more, had initiated the work of sampling the skeletons at ancient DNA lab more than a decade ago.
( With inputs from IANS )