Scientists have for the first time deduced through genetic evidence that mysterious human skeletons discovered decades ago around the shores of Roopkund lake in Uttarakhand represent distinct populations from India, the eastern Mediterranean and Southeast Asia.

The researchers from India, Germany and the US announced on Tuesday that their studies on 38 skeletons from Roopkund have revealed three groups of unrelated individuals who died in multiple events but broadly separated by about 1,000 years.

Roopkund is about 5,000 metres above sea level near Chamoli.

One group of 23 people with ancestries related to people from across India died between 600 AD and 900 AD, while a second group of 14 individuals with eastern Mediterranean ancestry died between 1600 AD and 1950 AD.

A single individual — the 38th skeleton — represented Southeast Asian ancestry.

“Only a part of the mystery is solved,” said Kumarasamy Thangaraj, a senior scientist at the Centre for Cellular and Molecular Biology, Hyderabad, a team member. “We still don’t know what these people were doing there and the circumstances in which they died and (why) their bodies were scattered around the lake shores.”

Skeletal remains scattered around the Roopkund lake site Picture courtesy:Himadri Sinha Roy

Since mountaineers found the skeletons in the 1940s, multiple proposals have been put forward to explain their origins. Some people have suggested that they were merchants or soldiers. According to local folklore, they are the remains of a king and queen and their attendants on a pilgrimage to the nearby Nanda Devi shrine who were struck down by the wrath of the goddess because of their celebratory behaviour.

Thangaraj and collaborating researchers at the Max Plank Institute for the Science of Human History and Harvard University have pointed out that Roopkund lake is not a major trade route but is a pilgrimage route to Nanda Devi. They said a “mass death” during a pilgrimage is a “plausible explanation” for the first group of skeletons.

The scientists have published their findings in the research journal Nature Communications.

“It could have been the result of a flash flood or a landslide — but this is speculation,” Thangaraj said.

The second group of skeletons with eastern Mediterranean ancestry has puzzled scientists. Although it would be tempting to propose that they were descendants of Indo-Greek populations established after the time of Alexander the Great, the individuals show neither mixed ancestry with South Asians nor inbreeding which would be expected if they were descendants of people from Alexander’s time.

“We’ve discovered the history of Roopkund lake is more complex than we ever anticipated,” David Reich, a senior geneticist at Harvard Medical School and a co-author, said in a media release. (This) raises the striking question of how migrants from eastern Mediterranean died in this place only a few hundred years ago.”